The Bicon SHORT Implant – A Thirty-Year Perspective

Second Edition

THE BICON SHORT IMPLANT

A Thirty-Year Perspective

Edited by Vincent J. Morgan, DMD

The Bicon Short Implant: A Thirty-Year Perspective, Second Edition

The Library of Congress has cataloged the first edition as follows:

Names: Morgan, Vincent (Vincent J.), editor. Title: The Bicon short implant : a thirty-year perspective / edited by Vincent Morgan. Description: Hanover Park, IL : Quintessence Publishing Co., Inc., [2017] | Includes bibliographical references and index. Identifiers: LCCN 2017016059 | ISBN 9780867157284 (hardcover) Subjects: | MESH: Dental Implants--trends | Dental Implantation--methods Classification: LCC RK667.I45 | NLM WU 640 | DDC 617.6/93--dc23 LC record available at https://lccn.loc.gov/2017016059

©2018 Quintessence Publishing Co, Inc

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Project Manager: Bryn Grisham Editor: Marieke Zaffron Design: Erica Neumann Production: Angelina Schmelter Printed in China

THE BICON SHORT IMPLANT

A Thirty-Year Perspective, Second Edition

Edited by Vincent J. Morgan, DMD

President Bicon Boston, Massachusetts

Berlin, Barcelona, Chicago, Istanbul, London, Milan, Moscow, New Delhi, Paris, Prague, Sao Paulo, Seoul, Singapore, Tokyo, Warsaw

Contents

In Memoriam: Dr William Bell viii Foreword by Dr William Bell ix Preface x Contributors xii

CHAPTER 1 / The History of Dental Implants 1

Jeffrey Lehrberg

CHAPTER 2 / Overview of the Bicon System 9

Vincent J. Morgan | Thomas Driskell

CHAPTER 3 / Characteristics of Implant-Abutment Prosthetic Systems: A Paradigm Shift 25

Estevam A. Bonfante | Marcelo Suzuki | Gerson Bonfante | Ronaldo Hirata | Ernesto Byron Benalcazar Jalkh | Adolfo Coelho de Oliveira Lopes | Vinicius P. Fardin | Paulo G. Coelho

CHAPTER 4 / Biologic Response to Dental Implants 37

Jeffrey Lehrberg | Paulo G. Coelho

CHAPTER 5 / Engineering Aspects of Bicon Implants 49

Soroush Irandoust | Jeffrey Lehrberg | Vincent J. Morgan | Sinan Müftü

CHAPTER 6 / The Influence of the Implant-Abutment Interface on Peri-implant Health 63

Giorgio Lombardo | Jeffrey Lehrberg | Jacopo Pighi | Joseph Leary | Peter Chaloupka | Mauro Marincola

CHAPTER 7 / The Survival of Short Implants 75

Somkid Tantirungkij | Joseph Leary

CHAPTER 8 / Treatment Planning and Basic Procedures 85

Muneki Hirayama | Drauseo Speratti | Laura Murcko

CHAPTER 9 / Anterior Implant Placement 103

Shadi Daher | Muneki Hirayama | Mauro Marincola | Laura Murcko | Luca de Micheli | Joseph Leary

CHAPTER 10 / Implant Placement in Adolescents 115

Vincent J. Morgan | Paolo Perpetuini | Muneki Hirayama | Shadi Daher | Laura Murcko | Tan Min Seet | Lee Fuen Fuen | Rudolf Seemann | Joseph Leary

CHAPTER 11 / Restorative Techniques 123

Paolo Perpetuini | Kristina Pisarik | Vincent J. Morgan | Estevam Bonfante | Katherine Morgan | Drauseo Speratti | Muneki Hirayama | Laura Murcko | Stefano Carelli | David M. Hallowes

CHAPTER 12 / Sinus Lift Techniques 151

Mauro Marincola | Shadi Daher | Rolf Ewers | Jeffrey Lehrberg

CHAPTER 13 / Ridge Splitting and the Split-Thickness Flap 181

Shadi Daher | Rolf Ewers | Andrea Cicconetti

CHAPTER 14 / Atrophic Maxillary Ridges 199

Rolf Ewers | Paolo Perpetuini | Rudolf Seemann | Tom De Wit | Imraan Sarvan | Marieke Coetzer | Kristina Pisarik

CHAPTER 15 / Atrophic Mandibular Ridges 215

Rolf Ewers | Paolo Perpetuini | Rudolf Seemann | Kristina Pisarik

CHAPTER 16 / Factors Affecting Bone Levels and Restorations of Short Implants 231

Rainier A. Urdaneta | Sung-Kiang Chuang | Joseph Leary | Vincent J. Morgan

CHAPTER 17 / Implant Placement in Compromised Tissue 253

Rolf Ewers | Vincent J. Morgan | Dusan Poruban | Paolo Perpetuini | Olga Davydova | Alexey Davydov | Igor Kostin | Stan Politis

CHAPTER 18 / Bone Voids 277

Mauro Marincola | Laura Murcko | Miguel Simancas-Pallares | Pieter Boshoff | José Luis Alonso Padilla

CHAPTER 19 / Bone Regeneration: Materials and Techniques 287

Shadi Daher | Mauro Marincola | Dusan Poruban | Laura Murcko | John Morgan | Jeffrey Lehrberg

CHAPTER 20 / Conclusion 317

Vincent J. Morgan

Index 319

In Memoriam

Dr William “Bill” Harrison Bell, DDS (1927–2016)

Last year, the dental community lost an innovator in the field of orthognathic surgery. Dr William H. Bell passed away of natural causes in June 2016, surrounded by family. We are truly honored that his foreword to this book is one of the last contributions he made in dental literature. His kind words accurately reflect his thoughtful spirit, living not for personal gain but working only to help others.

Dr Bell’s career in oral and maxillofacial surgery spanned over 55 years and has touched the lives of many, both directly in his role as a surgeon and through the surgical practices he helped to develop. His research has not only resulted in incredible advances to the Le Fort

I osteotomy but contributed to the development of orthognathic surgery and distraction osteogenesis. Unwavering in his pursuit of scientific advancement, Dr Bell authored innumerable articles and book chapters as well as the multivolume works Surgical Correction of Dentofacial Deformities and Modern Practice in Orthognathic and Reconstructive Surgery . Dr Bell has also won many awards for his groundbreaking research, including the American Association of Oral and Maxillofacial Surgeons Research Award, the William J. Gies Award, and the W. Harry Archer Award. In his years at the University of Texas and the Texas A&M Baylor College of Dentistry, he served as more than a teacher and mentor—many considered him a father figure as well.

Dr Bell will be greatly missed by not only his family, mentees, and colleagues whose lives he has undoubtedly shaped, but the entire oral and maxillofacial surgical community. While we mourn this great loss, we take comfort and pride in the fact that this man’s work will impact generations to come.

Foreword

If you know anything about the Bicon implant, you will know why it’s often called “the shortest implant with the longest history.” Since 1985, Bicon has been an innovator in short implants. Dr Vincent Morgan and his extended Bicon family have generously shared their knowledge of implantology, providing clinicians the world over with a versatile, reliable treatment for their patients.

This text is a succinct and accessible compilation of over 30 years of knowledge concerning the Bicon system. With everything from historical and theoretical origins to detailed step-by-step surgical and restorative guides, this book is a must-read for anyone interested in implantology.

My experience with Bicon, however, extends beyond the professional arena: my wife has two Bicon dental implants of her very own. Before discovering Bicon, all of my professional colleagues advised me that the only way my wife could receive dental implants would be with serious additional bone-grafting procedures. Then the colleague whom I sought to perform the procedure told me that bone grafting would be unnecessary if my wife received treatment with the Bicon short implant system. This was the only implant system available that allowed her to have bilateral mandibular implants—without the need for additional surgical bone-grafting procedures. For over 6 years now, my wife has been enjoying the benefits of her dental implants, and she has no complaints.

In summary, I highly recommend this book for not only clinicians looking to treat their patients with a unique system that offers a wealth of benefits, but also anyone interested in implantology in general. I join with the chorus of those delighted Bicon patients and clinicians throughout the world in commending the amazing achievements of the Bicon family.

William H. Bell, DDS (1927–2016)

Clinical Professor Department of Surgery University of Texas Southwestern Medical Center Dallas, Texas

Preface

The publication of this book is not, I hope, the culmination of my 50 years in dentistry, but only a progress report along the way on what has been an amazing journey with dental implants.

My journey began soon after graduating from dental school in 1970, when I treated a young Irish girl. I strongly advised her of two things: first, to move forward with the preparation of her maxillary canines and central incisors for two fixed bridges; and second, to abandon her foolish hope that one day a dentist would be able to insert two posts into her jaw to support prosthetic teeth for her congenitally missing maxillary lateral incisors. Fortunately, she did not listen to me. Several weeks after my conversation with the young lady, the dentist with whom I shared my practice lost the last of his posterior maxillary teeth. If he had been only a patient rather than a colleague, we would have advised the extraction of his remaining anterior teeth and the fabrication of a denture. However, since he was more than a patient, we decided to purchase two newly marketed Miter titanium blade implants. With no training of any sort, and with only common sense and logic as our guides, we successfully inserted the two blade implants into his posterior maxilla. Beginner’s luck being what it is, these blade implants outlived even him, still functional some 20 years later.

In our small dental practice, we dabbled with implants, including Tom Driskell’s promising Synthodont system, but it was not until we used the IMZ implant that we became earnestly involved. In 1992, after restoring over 2,500 implants with prosthetic screws and becoming frustrated with all of their inherent shortcomings, I had essentially given up on finding a perfect implant. By great good fortune, it was then that a professor of prosthetics, Robert Chapman, introduced us to the Stryker implant, which had a unique design with no screws. At last, we had found what we were looking for—a design characterized by logic and simplicity.

After we had successfully used their implant for 2 years, Stryker informed us that they were going to sell it: all rights, patents, and obligations. Of course, whoever purchased the implant would have to come to our practice, since we were its largest and most knowledgeable user, but Stryker did not consider us as a purchaser. We were dentists, not businessmen. Eventually however, the idea crossed their minds and ours, and as improbable as it seemed at the time, we bought the implant. The initial purchase was made possible by the magnificent generosity of our friend and attorney, Charles W. Sullivan. He provided us not only with bountiful startup capital but also with sage advice about owning a medical device company.

There have been many unsung heroes in the Bicon story, and I wish it were possible to name them all here, as my gratitude is sincere. We would be remiss, however, if we did not mention a courageous few who were with us during our earliest years when the future was uncertain. Singular among them was my wife, Debbie, who faithfully stood by me through all my struggles. With their intelligence and common sense, my twin sons, VJ and Craig, helped to provide the foundation for today’s worldwide Bicon business. Later, my son-in-law, Tom Peterson, would help solidify that foundation with his acumen and tremendous work ethic.

Without the innovative talents of Thomas Driskell, there would, of course, be no Bicon story to tell. We were able to get off the ground because of the generosity and optimism of Drs Norman Shepherd, Katherine Morgan, Allen Cail, Robert Chapman, Mauro Marincola, Shadi Daher, Muneki Hirayama, Drauseo Speratti, David Donohoe, Joe Leary, and our clinical staff. Without Angelo “Paolo” Perpetuini, we would have neither our Integrated Abutment Crown (IAC) nor our TRINIA prosthetics. Carl Nordin has tirelessly managed our creative and marketing efforts with his colleague Ilya Rivkin, and George Mihal has expertly administered our technical and digital world. Susan Fay has patiently arranged our worldwide travels for over two decades. We could never have succeeded without the understanding and support of United Titanium’s owner, Mike Reardon, and his management team, Fred Weekley and Charlie Gray; they are the ones who turn our ideas into reality—or in this case, titanium implants.

We have been fortunate in so many ways, but most importantly, we always seemed to come upon the right person at the right time. For example, my classmate, Boyd Tomasetti, introduced me to Dr Laura Murcko and to Prof Dr Rolf Ewers, who gave credibility not only to Bicon’s 4.0 × 5.0–mm implant and TRINIA prosthetics but also to the publication of this text. Visitors to our Boston headquarters are always impressed by our diverse and eclectic staff who are drawn from all corners of the earth. Bicon owes its phenomenal success to these talented and devoted professionals.

We started as dabblers in implantology in a small dental practice; we are now an international medical device company in 90 countries. How did we do it? We always looked forward: We concentrated on what we knew and what we wanted to achieve and did not concern ourselves with what others were saying or doing. We have known for years that the truth is a powerful ally and that it usually triumphs over time. Recently, a professor in Zurich greeted me by saying, “I know Bicon is a viable organization, for dead fish cannot swim against the stream. You have been going against the collective beliefs of the profession for decades, and now they are copying your ideas.”

We have been guided by the lesson of my Dominican friar teacher who said, “If it is logical, follow it; if it is illogical, avoid it, and you will be successful.” His words have proven steadfastly true.

The scientifically explained and clinically proven Bicon dental implant system offers a variety of unmatched clinical benefits for clinicians, technicians, and patients. This book provides readers with the theoretical background behind the Bicon implant system and detailed instruction for its use. Discerning clinicians and teachers of implantology should gain a clear understanding of not only the science behind the unique Bicon system but also the significant unmatched clinical benefits Bicon can provide for their patients and students. Simply stated, this book will show why, for over three decades, Bicon has provided a consistent and logical approach to implant dentistry for the primary benefit of patients.

Now we must ask: Where do we go from here? We shall remain committed to the Dominican logic and to telling the truth as we know it to be. We shall continue to focus primarily on the needs of patients and on supporting those professionals who provide for their care. We shall remain totally committed to patients and those who care for them by offering nothing less than the world’s finest dental implants. We shall focus on worthy goals like making our implants even shorter, and continue looking and moving in the best direction we know: forward.

Vincent J. Morgan

Note: Unless otherwise specified, all products referenced in this book are Bicon products.

Contributors

Estevam A. Bonfante, DDS, MS, PhD

Assistant Professor Department of Prosthodontics and Periodontology Bauru School of Dentistry University of São Paulo Bauru, Brazil

Gerson Bonfante, DDS, MS, PhD Professor Department of Prosthodontics and Periodontology Bauru School of Dentistry University of São Paulo Bauru, Brazil

Pieter Boshoff, DMD

Private Practice Limited to Maxillofacial Surgery Knysna, South Africa

Stefano Carelli, DDS Clinical Instructor Bicon Italy

Private Practice Limited to Odontology Rome, Italy

Peter Chaloupka, DMD

Private Practice Limited to Dental Implantology and Endodontics Garching bei München, Germany

Sung-Kiang Chuang, DMD, MD, DMSc

Clinical Professor Department of Oral and Maxillofacial Surgery School of Dental Medicine University of Pennsylvania Philadelphia, Pennsylvania

Private Practice Limited to Oral and Maxillofacial Surgery Brockton, Massachusetts

Andrea Cicconetti, MD, DDS

Assistant Professor Department of Oral and Maxillofacial Surgery University “Sapienza” Rome, Italy

Adolfo Coelho de Oliveira Lopes, DDS Researcher and Master’s Candidate Department of Prosthodontics and Periodontology Bauru School of Dentistry University of São Paulo Bauru, Brazil

Paulo G. Coelho, DDS, PhD

Leonard I. Linkow Associate Professor Biomaterials and Biomimetics College of Dentistry New York University

Hansjörg Wyss Department of Plastic Surgery Langone Medical Center New York University New York, New York

Marieke Coetzer, BChD

Private Practice Limited to Implantology and Restorative Dentistry Cape Town, South Africa

Shadi Daher, DMD

Clinical Assistant Professor Department of Oral and Maxillofacial Surgery Goldman School of Dental Medicine Boston University

Clinical Instructor Bicon

Private Practice Boston, Massachusetts

Alexey Davydova, MD, PhD

Professor Department of Oral and Maxillofacial Surgery Vice-Rector for Clinical Affairs Tver State Medical University Tver, Russia

Olga Davydov, DMD, PhD Assistant Professor Department of Postgraduate Dental Education Head of Implant Dentistry Center Tver State Medical University Tver, Russia

Tom De Wit, DMD

Private Practice Limited to Implantology and Prosthodontics Alken, Belgium

Thomas Driskell, BSc

Inventor of Bicon Implant and SynthoGraft Consultant, Technical Advisor Bicon Boston, Massachusetts

Rolf Ewers, MD, DMD, PhD

Chairman Emeritus University Hospital for Cranio Maxillofacial and Oral Surgery Medical University of Vienna

Chairman Cranio-Maxillo-Facial Institute Vienna, Austria

Vinícius P. Fardin, DDS, MS

Doctoral Candidate Department of Prosthodontics and Periodontology Bauru School of Dentistry University of São Paulo Bauru, Brazil

Lee Fuen Fuen, DMD

Private Practice Limited to General Dentistry Republic of Singapore

David M. Hallowes, MS

Director of Media Bicon Implant Dentistry Centre Boston, Massachusetts

Ronaldo Hirata, DDS, MS, PhD

Assistant Professor Department of Biomaterials and Biomimetics New York University New York, New York

Muneki Hirayama, DMD

Clinical Director Bicon Japan Tokyo, Japan

Clinical Instructor Bicon

Private Practice Boston, Massachusetts

Soroush Irandoust, BSc

Graduate Research Assistant Department of Mechanical Engineering Northeastern University Boston, Massachusetts

Ernesto Byron Benalcazar Jalkh, DDS

Master’s Candidate Department of Prosthodontics and Periodontology Bauru School of Dentistry University of São Paulo Bauru, Brazil

Igor Kostin, DMD, PhD

Department of Prosthodontics Implant Dentistry Center Tver State Medical University Tver, Russia

Joseph Leary, DMD Private Practice Limited to Periodontology Norwood, Massachusetts

Jeffrey Lehrberg, PhD

Research Scientist Department of Biomaterials Implant Dentistry Centre Boston, Massachusetts

Giorgio Lombardo, DDS Associate Professor Department of Dentistry and Maxillofacial Surgery University of Verona Verona, Italy

Mauro Marincola, DDS, MS

Professor Department of Implant Dentistry University of Cartagena Cartagena, Colombia

Clinical Director Bicon Europe Rome, Italy

Luca de Micheli, DDS Scientific Director Head of the Periodontal and Implantology Department Istituto Stomatologico Italiano

Private Practice Limited to Implantology, Periodontology, and General Dentistry Milan, Italy

John Morgan, DDS

Clinical Assistant Professor Department of Oral and Maxillofacial Surgery Goldman School of Dental Medicine Boston University

Clinician Implant Dentistry Centre

Private Practice Boston, Massachusetts

Katherine Morgan, DMD Clinical Instructor Bicon

Private Practice Boston, Massachusetts

Vincent J. Morgan, DMD President and Clinical Instructor Bicon

Private Practice Boston, Massachusetts

Honorary Professor Tver State Medical University Tver, Russia

Sinan Müftü, PhD

Professor Department of Mechanical Engineering Northeastern University Boston, Massachusetts

Laura Murcko, DMD Clinical Instructor Bicon

Private Practice Boston, Massachusetts

José Luis Alonso Padilla, DDS

Director of Implant Fellowship Program School of Dentistry Universidad Intercontinental Mexico City, Mexico

Clinical Instructor Graduate Prosthodontics and Implantology Program Instituto Ross Morelia, México

Paolo Perpetuini, CDT

Master Dental Technician Dental Laboratory Bicon Italy Rome, Italy

Jacopo Pighi, DDS

Research Scientist Clinic of Dentistry and Maxillofacial Surgery University of Verona Verona, Italy

Kristina Pisarik, BA

Media Specialist Bicon

Clinical Photographer Implant Dentistry Centre Boston, Massachusetts

Stan Politis, DMD

Chief of Medicine Department of Oral and Maxillofacial Surgery University Hospitals Leuven Leuven, Belgium

Dusan Poruban, MD, PhD

Assistant Professor Senior Consultant, Senior Lecturer Medical Faculty of Comenius University

Department of Oro-Maxillofacial Surgery Stomatological Clinica Saint Elizabeth Institute of Oncology Bratislava, Slovakia

Imraan Sarvan, BChD

Private Practice Limited to Maxillofacial and Oral Surgery Brackenfell, South Africa

Rudolf Seemann, MD, DMD, PhD Associate Professor University Clinic for Cranio Maxillofacial and Oral Surgery Medical University of Vienna Vienna, Austria

Tan Min Seet, DMD

Private Practice Limited to Oral and Maxillofacial Surgery Republic of Singapore

Miguel Simancas-Pallares, DMD, MSc

Assistant Professor — Assistant Professor Faculty of Dentistry University of Cartagena Cartagena, Colombia

Drauseo Speratti, DDS

Clinical Director Bicon Brazil São Paulo, Brazil

Clinical Instructor Bicon Boston, Massachusetts

Marcelo Suzuki, DDS

Associate Professor Department of Prosthodontics and Operative Dentistry School of Dental Medicine Tufts University Boston, Massachusetts

Somkid Tantirungkij, DDS, MS

Private Practice Limited to Maxillofacial Prosthodontics Chonburi, Thailand

Rainier A. Urdaneta, DMD

Private Practice Limited to Prosthodontics Worcester, Massachusetts

01

The History of Dental Implants

Jeffrey Lehrberg

While exploring the muddy banks of the Rio Ulúa—a location ominously named the “beaches of the dead”—archeologist and adventurer Dorothy Popenoe unearthed a fascinating discovery. Tucked away and preserved for over a millennium, the mandible of a young Maya woman was exhumed from its resting place. Boxed and cataloged, the ancient mandible was relegated to the recesses of a museum storage facility where it remained mostly forgotten for over 40 years. Dorothy Popenoe would never know the significance of her discovery: dating back to the year 600 ce, the mandible of the young Maya woman would turn out to be the oldest known example of a functioning dental implant.

Since its humble and ancient beginnings, the field of dental implantology has seen a plethora of changes, both in implant design and human understanding of the cellular and molecular underpinnings of dental implant biology. From the ancient Maya to the pioneers of modern-day titanium implants, this chapter examines the long and colorful history of dental implants.

Ancient Origins

Dental implants and their associated procedures might be considered a modern convention, but their origination can actually be traced back to ancient Mesoamerica. We are cognizant of the origins of dental implantology thanks mainly to the discoveries of Dorothy Popenoe and the careful eye of dental researcher and historian Amadeo Bobbio.

A husband-and-wife team of hobby-archeologists, Wilson and Dorothy Popenoe moved to Honduras in 1925, after Wilson Popenoe took the position of director of tropical agricultural experiments for United Fruit.[1] While preparing the construction site of the Lancetilla Agricultural Experiment Station, workers found a number of Maya artifacts—the discovery of which was fortunate for the couple, owing to their shared love of archeology.[1] Over the next few years, Dorothy unearthed and documented a great many artifacts found around her new Honduran home. Then, in 1931, while exploring a Maya dig site near the Rio Ulúa, she happened upon what appeared to be a human mandible with three sea shells embedded in the location of the central incisors (Fig 1-1a).[1,2] Unbeknownst to Dorothy at the time, the three shells in the mandible would turn out to be the earliest dental implants ever recorded. Unfortunately, Dorothy Popenoe would never learn the importance of her discovery; she died shortly after finding the mandible.[1] Fig 1-1 (a) The first functional dental implant. This human mandible, dating back to 600 ce, and its three mollusk shell teeth are the oldest evidence of osseointegrated dental implants. (Reprinted courtesy of the President and Fellows of Harvard College, Peabody Museum of Archaeology and Ethnology.) (b and c) Radiographs of the ancient Maya dental implants (600 ce) show the left side (b) and right side (c) of the mandible. The asterisks indicate the positions of the shell implants. (Reprinted with permission from the Journal of Dental History .[2] )

After Dorothy’s death, the mandible was shipped to the Peabody Museum at Harvard University, where it sat undisturbed for over 20 years.[1,2] The next time the mandible saw the light of day was in 1956, when the chairman of the Dental Implant Society of Great Britain, Boris Trainin, wrote to the Peabody Museum inquiring about the implants the mandible contained.[2] In response to Trainin’s inquiry, Dr J. O. Brew (acting director of the museum collection at the time) wrote back suggesting that the implants in question were probably part of a funeral ritual and had been placed posthumously.[2] The brief examination by Trainin and Brew appeared to confirm this, and the mandible was again stored away and remained mostly ignored for over 15 years. The rediscovery of the mandible, and the realization of its significance, may not have occurred if not for the keen eye of Amadeo Bobbio.

During his research into historical examples of dentistry, Prof Amadeo Bobbio stumbled upon the mandible while going through the catalog at the Peabody Museum. Despite the assessment by Trainin and Brew that the shells were placed posthumously, Bobbio decided that the mandible warranted reevaluation. Of course, at the time, finding ancient human remains possessing dental implants was definitely interesting but certainly not unprecedented (as made evident by Trainin and Brew’s assessment). Numerous jawbone fragments containing posthumously placed dental implants had been discovered at ancient Egyptian, Etruscan, and Phoenician archeological sites.[3–5] Nevertheless, Bobbio was able to recognize that there was something different and amazing about the implants in the Maya mandible.

What made this mandible so amazing was that unlike the other examples of ancient implants that had been found up until that point, the mollusk shells in the Maya mandible showed evidence of osseointegration (Figs 1-1b and 1-1c).[2] However, an even more amazing fact was that the radiographs taken of the Maya mandible showed a level of osseointegration similar to what is seen in modern-day titanium implants.[2]

Their incredible technologic and mathematic achievements notwithstanding, it is astonishing that the Maya were able to accomplish this feat of dental craftsmanship without the aid of modern imaging, antibiotics, or surgical tools. To put it into perspective, the prototypical Maya surgeon achieved the successful osseointegration of bioceramic implants at the same time King Arthur was purportedly searching for the Holy Grail. The fact that another successful dental implant procedure would not occur for another 1,400 years is a testament to the skill of this early Maya surgeon.

Early Attempts

Aside from the above example of the Maya mandible, evidence of implants or implant procedures (as we have come to define them today: endosseous, osseointegrated implants) existing prior to the 20th century is lacking. This does not mean, however, that the desire for functional tooth replacement escaped the ancient dental practitioner’s mind. Many scholars from the past have proposed ingenious methods to restore a missing tooth—usually in the form of a partial denture or crown. For example, Abu al-Qasim al-Zahrawi, a famous surgeon from the 11th century Abbasid Caliphate, suggested the use of ox bone prosthetics, which could be secured to neighboring teeth with wire.[6] Despite the creative prosthetic solutions suggested by early dental trailblazers, modalities involving the surgical implantation of biomaterials (including human teeth allotransplants) would not be seriously implemented until the 16th century.

Many of the first attempts to replace missing teeth in the 16th century involved using teeth obtained from human donors or domestic animals. The first written account of an implant procedure using human tooth allotransplantation occurred in 1562, with Ambrose Pare’s description of a successful allograft of a maxillary incisor (donated by a handmaiden—surely without coercion—to the noblewoman she served).[7,8] Just over 100 years later (based on descriptions from Charles Allen’s seminal text, The Operator for the Teeth , 1685) tooth transplantation was described as a common Renaissance-era procedure.[7] Be this as it may, even if tooth allografts were as prevalent as Charles Allen’s text suggests, the success of such procedures is undoubtedly questionable. The frequency of allotransplants and their success notwithstanding, concerns about infection (eg, fears of syphilis transmission), along with objections based on moral and ethical grounds (eg, stealing teeth from the dead), led to public outcry. Reports of tooth transplantation all but disappeared by the end of the 17th century.[6,9]

Unlike the ethical and moral quandaries that allogenic tooth implants raised (namely that they were forcibly taken from live donors or stolen from corpses), natural metal materials presented a more conscientious alternative. Along with its abundance and availability, advancements made in metallurgy, physics, and medicine during the industrial era allowed the use of metal to become the logical next step in dental implantology.

Fig 1-2 The first endosseous metal implant. Maggiolo’s implant, introduced in 1807, was designed to replicate a human tooth.

Maggiolo summarizes the usefulness of his implant system: “I have almost always obtained results that were as satisfactory to me as to the persons on whom I have operated.”[11] Although Maggiolo’s definition of satisfactory is unknown, there is no reason to doubt the success of his implant. In fact, in addition to his emphasis on aseptic technique, Maggiolo’s implant procedure shares many similarities with current two-stage implant surgeries.[11]

The remainder of the 19th century gave birth to a variety of implant shapes and materials, with clinical results ranging from catastrophic to outstanding. In the late 1880s, Drs S. M. Harris and J. M. Edmunds both experimented with implanting platinum posts coated with roughened lead.[12] Dr W. G. A. Bonwill tried his hand at implanting gold and iridium rods.[12] At the turn of the century, Dr R. E. Payne pursued the use of silver capsules attached to crowns as a method to replace missing teeth.[12] Even nonmetal materials such as rubber and porcelain were attempted, as illustrated by Dr C. R. Scholl’s use of a porcelain root in 1905.[12] Despite the multitude of different implant shapes and materials that were introduced during this period, it would take another decade before the true antecedents of modern dental implants would begin to fully emerge.

Greenfield’s Basket and Modern Implantology

Implantology in the Industrial Age

The first procedure involving the placement of an endosseous metal implant is attributed to Maggiolo in 1807.[2,3,10] Maggiolo’s implant was fashioned from three pieces of gold and designed to replicate the root of a human tooth (Fig 1-2).[11] In his monograph , Le Manuel de l’art du dentiste ,

Arguably one of the most important and unrecognized heroes of dental implantology is E. J. Greenfield, a man whose implant system has the distinction of being the predecessor of all modern implants. Consisting of an endosseous implant and fixed abutment and crown combination, Greenfield revealed his system and surgical procedure in Fig 1-3 The Greenfield Basket. The iridium-platinum basket (a) attached to a 24-karat gold head with porcelain crown (b) and the “tubular knife” (c) used for the surgery. (d) A cross-section of the alveolar crest shows the implant in situ. (Modified from Greenfield[12] ).

1913.[12] Struck with the idea for a dental implant after observing an orthopedic fracture surgery involving the use of silver-wire suture, Greenfield devised an implant of an iridium-platinum wire alloy that possessed a basket-like design (Fig 1-3).[12] The iridium-platinum basket was soldered to a 24-karat gold head, by which the crown could be attached.[12]

Greenfield reported performing eight successful implant procedures using his iridium-platinum design; each procedure had healing times and outcomes analogous to modern-day implant procedures (Fig 1-4).[12] Perhaps the most impressive aspect of Greenfield’s report was his explanation of the mechanism behind his procedure. In what reads like a proposed mechanism from a modern-day journal, Greenfield speculated as to what was happening at a cellular level, in and around his implants, with eerie accuracy considering his limitations. (There is no evidence that he performed histology as there is no mention of it in his text 12.) Thus, Greenfield became the first researcher to describe the process of osseointegration (though it would not be called this for another half century).[12,13] Moreover, Greenfield was so ahead of his time that aspects of his implant system were still being incorporated into implant designs as late as the 1970s.[13,14]

Despite Greenfield’s reported success with his implant system (known in the dental community as the “Greenfield Crib” or the “Greenfield Basket”), it was nevertheless controversial. In the years that followed its release, ambitious dentists would modify Greenfield’s design and procedure, looking to cut corners or make what they considered improvements.[15] When these modified implants failed, blame was placed on Greenfield’s design rather than the impromptu modifications themselves. Adding to Greenfield’s troubles were prominent dentists of the day who believed that Greenfield’s implants would eventually fail and that implantology itself did not represent a realistic treatment with any possible future.[11,15]

Fig 1-4 Postoperative radiograph showing a Greenfield Basket. (Reprinted from Greenfield[12] ).

Even the more forward-thinking clinicians who did recognize the potential of dental implants were often at odds with Greenfield’s interpretation of his results.[11,15,16] An example of this can be found in a 1914 report on conical implants, where H. J. Peter asserted that implant stability was achieved via a thick connective tissue that forms around the implant, as opposed to the bone that grew within its core, as claimed by Greenfield.[15] Though we now know that Peter was describing fibrous encapsulation (a cause of implant failure and arguably the antithesis to osseointegration), he was still able to use Greenfield’s method—albeit modified with the addition of a bismuth iodine paraffin paste, different implant design, and surgery. Peter was still able to achieve an 80% survival rate despite his disagreement with Greenfield regarding the mechanism of implant stability.[15] Peter’s modifications to Greenfield’s design appeared to be successful; however, other clinicians were not so lucky.

It only took 2 years before Greenfield’s implant was roundly stigmatized. The meeting notes from the 1914 New Jersey State Dental Society are particularly unfavorable to Greenfield’s system. Dr H. J. Kauffer (in the introduction to his implant pilot study presented at the meeting) states “[Greenfield’s] operation has been abandoned owing to the large percentage of failure.”[17] In the discussion that followed Kauffer’s presentation, Dr A. E. Smith added how he had placed a number of Greenfield implants with varying success.[17] Despite Smith’s mixed results (and the admission that he himself had a Greenfield implant in his own mouth), he stated that he would be abandoning the Greenfield system for one of his own creation.[17]

Especially considering that aspects of Greenfield’s design were incorporated into modern implants, it is conceivable that, rather than some intrinsic design flaw, the allegedly high number of Greenfield implant failures resulted from causes such as improper loading, incorrect surgical procedures, or lack of proper hygiene.[13] Whatever the reason for the high number of failures, Greenfield’s implant system was all but abandoned by the dental community after a few short years.

According to critiques of Greenfield’s system in the years that followed, one possible reason for its failure was the choice of material. Greenfield does not expound on his rationale for using iridium-platinum alloy; he merely states, “It is impervious to acids, and does not injure the tissue which grows about it.”[12] However, it is fortunate that Greenfield chose this iridium-platinum, as an alternative metal might have yielded far worse results. A report by Dr A. A. Zierold, published 11 years after Greenfield’s implant article, confirmed that different materials did in fact elicit different reactions from tissues.[13,18] Zierold’s report, along with others like it, were some of the first that tackled the topic of implant biocompatibility—a topic that subsequently placed increased focus not only on implant design, but on the composition of materials as well.

Advances in Implant Composition and Design

Weary of the seemingly haphazard selection of dental implant materials by researchers and clinicians, along with the ambiguous description of research methods ubiquitous throughout the literature, Drs C. S. Venable, W. G. Stuck, and A. Beach set out to determine which metals were best tolerated by bone.[19] After testing a wide variety of pure metals and alloys, Venable et al determined that the alloy Vitallium, consisting of chromium, cobalt, and molybdenum, “showed complete resistance to body fluids and no changes whatever in either the surrounding tissues or in the bone.”[19] At the time of their study, the examination of electrical influences of different metals on tissues had emerged as a hot topic in science, generating a surge in research. Three years after Venable et al published their report in 1937, another group studying the electrolytic impact of multiple metals embedded in bone made a seemingly trivial observation that would turn out to have far-reaching implications.[20]

As was the case with other researchers of the day, R. T. Bothe, K. E. Beaton, and H. A. Davenport were curious how tissues responded to the electrolytic behavior of dissimilar metals.[20] Although they mainly focused on Vitallium (based on its properties demonstrated by Venable et al), the researchers also evaluated the biologic response to two previously untested metals: manganese and titanium.[20] Using cats as their experimental animals, Bothe et al drilled 1.5-mm-diameter holes into their femurs and then inserted anywhere from one to four metal pegs of varying composition (Fig 1-5).[20] The electrolytic activity was unremarkable; however, Bothe et al happened to comment on the response of bone to titanium: “Titanium was fully as well tolerated as Vitallium and stainless steel, perhaps better in that the bone had a tendency to grow into contact with it.”[20] The description by Bothe et al in their report—of bone growing into contact with titanium—would be the first description of titanium implant osseointegration.[20] Although the report by Bothe et al showed that titanium was superior to the other metals tested, both its price and its limited accessibility prevented its implementation as a potential biocompatible implant material for over a decade.[20,21] Fig 1-5 Radiographs of cat femurs implanted with various metal pegs, taken 224 days after surgery. Implantation sites on a given femur are indicated by black arrows . Mg, Magnesium; Mn, Manganese; Ti, Titanium; Vit, Vitallium; Cu, Copper. (Reprinted with permission from the Journal of the American College of Surgeons[20] ).

Eleven years after Bothe et al published their report, new manufacturing methods allowed titanium to become more available and less costly. This increased availability at a lower price caused titanium to be reevaluated as an implant material.[21] Gottlieb S. Leventhal, a researcher at Mount Sinai hospital, decided to follow up on Bothe’s findings: Leventhal tested the biologic effect of titanium placed in both subcutaneous tissue and bone.[21] Similar to the results seen by Bothe et al, Leventhal in 1951 found that bone readily adhered to titanium.[21] However, unlike Bothe et al, Leventhal quickly saw the potential of titanium in the field of medicine, going so far as to state that it represented the ideal metal for both fracture fixation and surgery in general.[21] Sadly, the contributions of Bothe et al and Leventhal have been mostly forgotten; they are not credited with the “discovery” of titanium osseointegration, and their manuscripts are difficult to access. Instead, history has given credit for the discovery of osseointegration to the man who conceived the term itself.

Early Pioneers of the Modern Era

Similar to what was seen toward the end of the 19th century, the 1950s and 1960s experienced an explosion of new implant designs. Unlike the regulatory standards in place today, medical devices devised in the mid-20th century did not require stringent evaluation prior to their release; this ultimately led to a relaxed atmosphere where implant designs and modifications were extemporaneously concocted.[22] Although many implant innovators of the day were dentists in private practice, oftentimes operating with a cavalier attitude toward the scientific method, one researcher in particular stands out for his more methodical approach: Per-Ingvar Brånemark. Thanks to Brånemark’s disciplined methods and the overall quality of his research, endosseous dental implants were brought into the realm of mainstream dentistry. Brånemark also stands out in this time period because he coined the term osseointegration .

Brånemark’s decision to work on osseointegration began accidentally.[3,23,24] During his investigations into the vascularization of rabbit bones, Brånemark noticed that the in vivo titanium microscope chambers had become infused with bone, making them exceedingly difficult to remove.[3,24,25] With the help of otolaryngologists and plastic surgeons at his university, Brånemark began experimenting with titanium fixtures as a means to repair bone defects and edentulous sites.[24,25] However, a major difference between the research performed by Brånemark et al and that of other contemporary implant experimenters was their strict adherence to aseptic guidelines: each experimental implant was properly sterilized and placed using aseptic surgical techniques in a hospital setting.[22] Another difference that separated Brånemark et al from researchers of the day was their longitudinal studies. In Brånemark’s 1969 animal study, dental implants placed in dogs were shown to survive after 5 years (the endpoint of the experiment).[25] Previous long-term reporting of implant experiments up until that point had mainly consisted of anecdotal data.[11]

In 1965, following their successful study of titanium implants in animal models, Brånemark and his team began clinical trials that continued for 10 years; it was here in their report of the results that Brånemark first used the word osseointegration to describe the regeneration of bone around titanium implants.[26] Brånemark’s report was extremely thorough: implant response was examined on both a physiologic and psychosocial level using a variety of techniques.[26] However, despite Brånemark’s rigorous research approach, the dental community responded with skepticism to his findings.[27] Nonetheless, Brånemark and his colleagues were able to convince the dental community that endosseous dental implants were not only possible, but that they represented the future of implant dentistry.

A Revolution in Implantology

The wide assortment of implant designs proposed during the period leading up to the late 1960s is a testament to the creativity of their creators. To mention every design and inventor is beyond the scope of this book; however, there are some landmark designs worth mentioning. Leaders in the field, such as Formiggini in the late 1940s, and later Cherchieve in the 1950s (who originally advocated the use of block implants), proposed screw-type designs in the shape of a helix (Fig 1-6).[22,28]

Leonard Linkow—who along with Brånemark should be considered one of the great early pioneers of implantology—was a proponent of unique designs such as his blade implants and of more conventional designs such as his vent-plant self-tapping implants (Figs 1-7 and 1-8).[3,22,29] Finally, other designers presented deviations from the screw root form (SRF) implant used by Brånemark that are ubiquitous today. Among the great many nascent implant designs of the 1960s emerged a unique and oddly shaped implant called the plateau-root form (PRF) or finned implant. Created by inventor Thomas Driskell, the PRF implant possessed a unique macrogeometry that would go on to serve as the basis for all future Bicon implants.

The development of the antecedent of the Bicon implant began at the Battelle Memorial Institute in Columbus, Ohio. Toward the end of 1968, as the Vietnam conflict was beginning to escalate, Driskell and his team initiated studies aimed at addressing the rapid and effective restoration of missing teeth in a combat or field situation.[30] Encouraged by the promising advancements made with ceramic materials, Driskell and his team sought to develop a freestanding alumina-coated root structure that would be stronger than plastic or acrylic implants and require less healing time than metallic implants. (Owing to the two-stage technique, procedures that used metallic implants could take 4 to 6 months.[31] ) Using monkeys as their experimental organism, Driskell et al evaluated a number of designs with different surface properties, all of which possessed a macrogeometry that was a general approximation of mammalian teeth (Fig 1-9).[32]

The initial implants used in Driskell’s studies were smooth, since his rationale was that the surface would act as a pseudo-cementum, and Sharpey’s fibers would secure the implant in place.[22,32] However, after uncovering and loading the smooth implants, most of them failed.[32] Subsequent implant designs included a porous surface, a coarse surface, and a porous surface with a “grooved or corrugated pattern” (Fig 1-10).[32] By systematically testing each design, Driskell et al discovered that the bifurcated grooved or finned design resulted in greater bone-implant contact compared with other designs.[22] Furthermore, the grooved design (henceforth referred to as PRF design ) permitted occlusal loads to be transferred onto the bone that infiltrated the space between grooves.[22] The bifurcated grooved design later evolved into the single root type II implant, which was the antecedent of all modern Bicon implants (Fig 1-11).[22,32]

In the mid-1970s, Driskell took his findings to Miter, Inc, where a spin-off of the type II design called the Synthodont implant (Miter) was released for commercial use (Fig 1-12). Like the implants devised in the Battelle studies, the Synthodont implant was made from high-density alumina and

Fig 1-6 Illustration of a typical helix implant like those proposed by early pioneers such as Formiggini and Cherchieve.

Fig 1-7 Illustration of Linkow’s blade implant. The idea was that the blade at the bottom of this illustration could be inserted in narrow alveolar crests and preclude the need for bone regeneration surgery.

Fig 1-8 Illustration of Linkow’s selftapping vent-plant implant.

Fig 1-9 Depiction of Driskell’s alumina implant and crown. The early alumina implants were smooth and possessed a macrogeometry that was a general approximation of mammalian teeth.

Fig 1-10 Illustration of Driskell’s grooved or corrugated implant. Driskell’s later implants were finned and bifurcated.

Fig 1-11 The type II implant. The Fig 1-12 The Synthodont implant. Fig 1-13 The Titanodont implant. single-root, finned design of the type II implant is the antecedent of all modern Bicon implants.

was a freestanding, nonsubmergible implant. Despite evidence of osseointegration, the Synthodont’s nonsubmergible design and lack of specialized surgical instruments resulted in unpredictable outcomes.[22] Even in the most skilled of hands, the implant required splinting and had to remain out of function to ensure osseointegration took place.[22] To overcome the challenges that nonsubmergible implants presented, the Synthodont implant further evolved into the Titanodont (Miter), a submergible implant made of titanium and with a removable abutment (Fig 1-13).[22] The Titanodont was special not only for its PRF design, but also because it was the first implant to possess an acid-etched surface. Most impressive of all, however, was that the Titanodont saw the implementation of a locking-taper implant-abutment interface, a characteristic that provided 360 degrees of abutment positioning and a bacterial seal.[22]

Bicon’s Beginnings

After serving as the director of research for Miter, Driskell and his partners formed a company called DB Bioengineering. In October of 1985, DB Bioengineering received premarket notification for the DB Precision Fin Implant System—an implant based on Driskell’s Batelle Institute designs (Fig 1-14). Although it retained the PRF design and locking taper of its predecessors, the DB Precision Fin Implant had new features that would set it (and all modern Bicon implants) apart from its competitors: a sloping shoulder, short overall length, specialized titanium instruments, and the implementation of slow-speed drilling.

Two years after this unveiling, DB Bioengineering was sold to the multinational conglomerate the Stryker Corpo-

Fig 1-14 The DB Precision Fin implant possessed all of the features of modern Bicon implants, including a PRF macrogeometry, locking-taper implant-abutment interface, sloping shoulder, and shorter overall length.

3. Abraham CM. A brief historical perspective on dental implants, their surface coatings and treatments. Open Dent J 2014;8:50–55.

4. Forshaw RJ. The practice of dentistry in ancient Egypt. Br Dent J 2009;206:481–486.

5. Irish JD. A 5,500 year old artificial human tooth from Egypt: A historical note. Int J Oral Maxillofac Implants 2004;19:645–647.

6. Ring ME. Dentistry: An Illustrated History. New York: Abradale Press, 1992.

7. Noble HW. Tooth transplantation: A controversial story. History of Dentistry Research Group Newsletter, 2002.

8. Forrai J. Ambroise Paré - The “Father of Surgery.” Rev de Clin Pesq Odontol 2006;2:447–450.

9. Atkinson ME. Histopathological and immunological aspects of tooth transplantation. J Oral Pathol 1978;7:43–61.

10. Jourdan, Maggiolo. Le Manuel De L’art Du Dentiste. 1807.

11. Kirk EC. Academy of Stomatology of Philadelphia regular monthly meeting. Dental Cosmos 1913;55.

12. Greenfield EJ. Implantation of artificial crown and bridge abutments. Dental Cosmos 1913;55:364–369.

ration, where the DB Precision Fin Implant was renamed the Stryker Precision Fin Implant.[33] In 1994, Stryker sold the Precision Fin Implant System to a group of entrepreneurs in Boston who would later name their company Bicon (a combination of bi and con , reflecting the simple two-part design of the implant/abutment connection).

13. Rudy RJ, Levi PA, Bonacci FJ, Weisgold AS, Engler-Hamm D. Intraosseous anchorage of dental prostheses: An early 20th century contribution. Compend Contin Educ Dent 2008;29:220–229.

14. Scacchi M. The development of the ITI dental implant system. Part 1: A review of the literature. Clin Oral Implants Res 2000;11(suppl 1):8–21.

15. White JD, McQuillen JH, Ziegler GJ, White JW, Kirk EC, Anthony LP. Dental Cosmos. SS White Dental Manufacturing Company, 1915.

16. Harlan AW, Johnson CN. The Dental Review: A Monthly Journal Devoted to the Advancement of Dentistry 1914;28.

17. Ottolengui R. Dental Items of Interest: A Monthly Magazine of Dental Art, Science and Literature 1915;37.

18. Zierold AA. Reaction of bone to various metals. Arch of Surg 1924;9:365.

The Future of Implantology and Beyond

Since its humble beginnings in ancient Mesoamerica, the tools and techniques of dental implantology have come a very long way. Breakthroughs in materials science and understanding of biology have allowed the safety and efficacy of dental implants to proceed in leaps and bounds. Furthermore, new and emerging technologies continue to allow us to further elucidate the biologic underpinnings of implant success in terms of survivability and extent of osseointegration—both of which are the focus of subsequent chapters of this book.

Since its creation, the Bicon implant has undergone several groundbreaking innovations and improvements, all the while staying true to its time-tested design. Similarly, Bicon as a company has stayed true to its commitment to quality and excellence, along with its drive to propel advancements in implantology and aesthetics. New materials such as the versatile TRINIA material and new designs such as the Universal Abutment with milled retentive copings for telescopic restorations signify a paradigm shift in implantology. With these new innovations and discoveries, Bicon is paving the way to the future.

References

19. Venable CS, Stuck WG, Beach A. The effects on bone of the presence of metals; based upon electrolysis: An experimental study. Ann Surg 1937;105:917–938.

20. Bothe RT, Beaton KE, Davenport HA. Reaction of bone to multiple metallic implants. Surg Gynecol Obstet 1940;71:598–602.

21. Leventhal GS. Titanium, a metal for surgery. J Bone Joint Surg Am 1951;33A:473–474.

22. Driskell TD. History of implants. CDA J 1987;15(10):16–25.

23. Chug A, Shukla S, Mahesh L, Jadwani S. Osseointegration—Molecular events at the bone–implant interface: A review. J Oral Maxillofac Surg Med Pathol 2013;25:1–4.

24. Brånemark PI. Osseointegration and its experimental background. J Prosthet Dent 1983;50:399–410.

25. Brånemark PI, Adell R, Breine U, Hansson BO, Lindström J, Ohlsson A. Intra-osseous anchorage of dental prostheses. I. Experimental studies. Scand J Plast Reconstr Surg 1969;3:81–100.

26. Brånemark PI, Hansson BO, Adell R, et al. Osseointegrated implants in the treatment of the edentulous jaw. Experience from a 10-year period. Scand J Plast Reconstr Surg Suppl 1977;16:1–132.

27. Albrektsson T, Wennerberg A. The impact of oral implants - past and future, 1966-2042. J Can Dent Assoc 2005;71:327.

28. Cherchieve R. Considerazioni Fisiologiche E Pratiche Su Una Osservazione Originale Di Un Impianto Endosseo. Inform Dent 1959;24:677–680.

29. Linkow LI. Clinical evaluation of the various designed endosseous implants. J Oral Implant Transplant Surg 1966;12:35–46.

30. Driskell TD, O’Hara MJ, Niesz DE. Surgical Tooth Implants, Combats and Field. Columbus: Battelle, 1972.

31. Driskell TD, O’Hara MJ, Greene GW. Surgical Tooth Implants, Combat and Field. Ft Belvoir, VA:Defense Technical Information Center, 1971.

32. Driskell TD, McCoy LG, Tennery VJ, Niesz DE. Surgical Tooth Implants, Combat and Field, Report Number 3: Annual Report. Columbus: Battelle, 1973.

33. McKinney RV. Endosteal Dental Implants. St. Louis: Mosby Year Book, 1991.

34. Claassen C. Women in Archaeology. Philadelphia: University of Pennsylvania, 1994.

35. Bobbio A. The first endosseous alloplastic implant in the history of man. Bull Hist Dent 1972;20:1–6.

02

Overview of the Bicon System

Vincent J. Morgan | Thomas Driskell

Origins of the Bicon Implant

The origins of the Bicon Implant System can be traced back to 1968 with the United States Army’s funding of Thomas Driskell’s development of a freestanding single tooth replacement implant at Battelle Memorial Institute in Columbus, Ohio. Driskell’s initial implant design—the Synthodont implant (Miter)—was made of a high-density aluminum oxide.[1] In 1981, Driskell introduced the Titanodont (Miter), an implant made of surgical-grade titanium alloy (Ti-6Al-4V).[2] Titanium’s compatibility with bone and consequent merits for surgery were recognized as early as 1940 by Bothe et al[3] and later in 1951 by Gottlieb Leventhal.[4] The current design of the Bicon implant was introduced in 1985 as the DB Precision Fin Implant (DB), subsequently known as the Stryker Precision Fin Implant (Stryker). Since 1994, this uniquely designed short, plateau-root form (PRF) implant has been known as the Bicon implant (see chapter 1). Thanks to the steadfast design and precision crafting under the supervision of Fred Weekley at United Titanium in Wooster, Ohio, all components and instrumentation manufactured in 1985 are still fully compatible with the modern Bicon implants of today.[5]

The Science Behind the Design

In 1892, German surgeon Julius Wolff[6] published his seminal observation that bone changes its external shape and internal cancellous architecture in response to stresses acting on it (Figs 2-1 and 2-2). Wolff’s[6] law of bone modeling and remodeling, and the subsequent work performed by Frost,[7] provide the physiologic framework behind Bicon’s time-proven and clinically successful implant design (see chapter 4). Fig 2-1 An example of bone modeling and remodeling around Bicon implants. (a) Preoperative radiograph. (b) Postsurgical radiograph taken on insertion day. (c) Four-year follow-up radiograph. Fig 2-2 Histologic sections showing bone modeling and remodeling around a Bicon implant in situ for 14 years (a) and 23 years (b) . Fig 2-3 This quadriplegic patient used his Bicon implant as both a tooth and a surrogate hand, reflecting the efficient transfer of occlusal forces into surrounding bone and consequent strength of the implant. (a) Radiograph 25 years after insertion. (b) Clinical appearance 25 years after insertion. (Courtesy of Dr Don Rothenberg, Marblehead, Massachusetts.)

Achieving the current Bicon design required the understanding and application of many biologic, mechanical, and metallurgic principles, along with over 30 years of clinical and laboratory trials. A significant engineering challenge for dental implants has always been the efficient transfer of occlusal forces from the prosthesis to the bone surrounding the implant, especially where freestanding, unsplinted restorations are concerned. Owing to the PRF design of Bicon implants, this engineering challenge has been overcome, as the design allows for very short, narrow implants to efficiently transfer forces into bone. The Bicon implant’s ability to transfer occlusal forces is exemplified in the case of a quadriplegic patient who used his implant and prosthesis as both a tooth and surrogate hand (Fig 2-3).

In developing the Bicon implant, every design aspect was thoroughly accounted for; the result is an outstanding clinical success, achievable through the seamless integration of the implant’s individual features. Thus, it is the totality of Bicon’s implant design that makes it unique and provides clinicians and patients with a wide range of clinical capabilities. Fig 2-4 (a) Key features of the Bicon dental implant system: restorative flexibility, extraoral cementation and Integrated Abutment Crowns (IACs), platform switching, sloping shoulder, locking-taper implant-abutment interface (IAI), plateaued and tapered macrogeometry, short overall length and narrow width, and use of slow drilling. (b and c) Transfer of angled occlusal forces into implants and surrounding bone. (b) A long, cylindric implant has occlusal forces applied at an angle. This causes stress only at points indicated by the green arrows and not throughout the central length. Large areas of bone adjacent to the implant that are not involved in occlusal force transfer are indicated by blue lines . (c) When occlusal forces are applied at an angle to a Bicon implant, the forces are absorbed by bone within the plateaus. Directions of forces are indicated by the green arrows .

Key Attributes of the Design

Bicon’s unique design and unmatched clinical capabilities distinguish it from other implant systems (Fig 2-4a). Since its inception, the Bicon implant system has maintained a series of core design features and attributes:

• Plateaued and tapered macrogeometry

• Sloping shoulder

• Bacterial seal

• 360-degree abutment positioning

• Hemispheric abutment base

• Slow drilling

• Short length

• Narrow width

• Peri-implant bone gain

These key design features and attributes provide for Bicon’s clinical success and are examined in more detail in the sections that follow. Fig 2-5 (a) Threaded implants initially cause pressure necrosis of the bone, whereas Bicon plateaus immediately provide for cortical-like Haversian bone formation. (b) After the initial bone necrosis, threaded implants provide for the formation of a slower-growing appositional bone without blood vessels, whereas the bone chambers of the Bicon plateaus provide for a faster-growing cortical-like Haversian bone with blood vessels. (c) The appositional bone around threaded implants and the cortical-like Haversian bone around Bicon implants have significantly different mechanical properties, which accounts for why Bicon short implants can provide clinical capabilities that threaded implants cannot.

Plateaued and tapered macrogeometry

When discussing implants, it is important to acknowledge what may not be obvious: an implant, unlike a normal healthy tooth, is an ankylosed structure; therefore, the normal occlusal range of forces is transmitted directly into the bone. The Bicon implant design distributes these occlusal forces through the use of plateaus or fins. This design element has expanded the implant’s load-bearing capacity to a startling extent, all the while protecting the implant and restoration from fracture and protecting surrounding bone from undue stress. The plateaus on a Bicon implant successfully dissipate the forces generated via normal chewing (and even during parafunctional activity such as bruxism) by effectively dissipating them from the plateaus into the surrounding bone. The surrounding bone then treats these dissipated forces as acceptable strains that stimulate the continued development of a cortical-like bone with central vascular systems.[8]

The plateaus on Bicon implants provide approximately 30% more surface area than comparably sized threaded implants.[9] More importantly, the plateau design results in the formation of intramembranous-like, fast-growing bone (ie, 20–50 μm per day) that possesses unique cortical-like Haversian structures[9,10] (see Fig 2-2). This cortical-like bone possesses different clinical capabilities than the slower-forming (1–3 μm per day) appositional bone seen around threaded implants[9,10] (see chapter 4). One could think of the Bicon implant anchored in its cortical-like Haversian bone as having better mechanical properties than threaded implants surrounded by appositional bone, analogous to a post secured in cured concrete having better mechanical properties than a post seated in soil (Figs 2-4b and 2-5).

Cortical-like Haversian bone is not the only benefit of the plateau design: The plateaus transfer compressive forces into the bone throughout the entire length of the implant body. Compressive occlusal forces are absorbed by the bone within the plateaus and then propagated out to the surrounding bone, a feature especially important when forces are applied at an angle; unlike Bicon implants, threaded or cylindric implant designs do not absorb occlusal forces in this manner and thus are limited in their potential to adapt to increased occlusal loads.[11,12]

Sloping shoulder

The coronal-most part of a Bicon implant, also known as the implant’s shoulder, slopes inward; this sloping shoulder provides space to promote the development of healthy interdental papillae and subsequent placement of an aesthetic restoration, even when implants are in close proximity to other implants or teeth[13] (Fig 2-6). Aesthetic-looking papillae require sufficient space and bony support: The sloping shoulder design provides sensible biologic space where bone can grow and support such aesthetic papillae[14] (Fig 2-7). As far back as 1968, long before the term platform switching was coined, Driskell’s design of the sloping shoulder allowed for this bone growth. In fact, the Bicon design has a double platform switch. The first platform switch occurs between the wide implant body and the narrower abutment shaft. The second occurs between the abutment Fig 2-6 The sloping shoulder provides space for bone growth, which provides support for healthy and aesthetic interdental papillae.

Fig 2-7 The sloping shoulder supports healthy, aesthetic papillae. (a and b) Aesthetic papillae in the maxilla: (a) Clinical appearance of closely spaced maxillary implants after 15 years. (b) Radiograph at the 15-year follow-up. (c to f) Aesthetic papillae in the mandible: (c) Postinsertion radiograph. (d) Papillae on insertion day. (e) Papillae at 1-year follow-up. (f) Papillae at 3-year follow-up.

shaft and the wider hemispheric base of the abutment. It also acts as a loading mechanism, creating another plateaued space for bone between the sloping shoulder of the implant and the abutment’s hemispheric base (see Fig 2-4).

Bacterial seal

Unlike implant systems that utilize a screw-in or screw-in tapered implant-abutment interface (IAI), Bicon implants secure the abutment to the implant by means of a 1.5-degree locking taper. Locking-taper IAIs provide several benefits to patients and clinicians. For example, abutments can be easily inserted and removed, even after long periods, with the simple use of extraction forceps. Similarly, a locking-taper IAI allows for easy rotational adjustments prior to, during, and even after the seating of a restoration.

By virtue of their connection method, locking-taper IAIs create a seal that prevents bacteria from contaminating the interior of the implant. Possessing a bacterial seal at the IAI eliminates the bacterial flux associated with clinical odors, unpleasant tastes, soft tissue inflammation, and bone loss commonly observed with threaded abutment connections.[15–17] The deleterious effects of harmful bacteria and micromovement on gingival tissues and alveolar bone cannot be overstated; an in-depth discussion on the Bicon locking-taper IAI, and the effect of bacterial contamination on peri-implant health, can be found in chapter 6. In addition to providing a bacterial seal, the locking taper also provides for 360 degrees of universal abutment positioning, allowing easy, chairside positioning and modifications to take place.

360 degrees of abutment positioning

An additional benefit of a locking-taper IAI is 360 degrees of universal abutment positioning. This characteristic allows multiple abutments to be easily paralleled, even in the case of nonparallel implants (Fig 2-8). This feature is especially useful when orienting and seating multiple abutments to a prosthesis (Fig 2-9). Having 360 degrees of positioning also permits the easy use of angled abutments and allows for the cementation of crowns to take place extraorally. Moreover, fixed partial dentures can be bonded intraorally, eliminating the need for cutting, indexing, and soldering partial denture frameworks. Finally, the locking-taper IAI with its 360 degrees of positioning allows the creation of aesthetic restorations even when implants are not ideally positioned.

Hemispheric abutment base

The hemispheric base has been an integral feature of Bicon’s abutment design since its inception; however, only recently have the full merits and functions of this geometry been recognized. As reported by Urdaneta et al,[13] the hemispheric base of the abutment acts as a loading Fig 2-8 The 360 degrees of abutment positioning allows multiple abutments to be easily paralleled, even in the case of nonparallel implants. (a) The first abutment is inserted. (b) The second abutment is inserted. (c) The postinsertion radiograph illustrates the nonparalleled implants with a TRINIA prosthesis, which was restored in only two clinical visits.

Fig 2-9 A TRINIA prosthesis is used to orient and seat four Bicon abutments. Orienting and seating four abutments in this manner is easily performed because of the locking-taper IAI.

Fig 2-10 The hemispheric base transmits occlusal force into the bone beneath it. Green arrows indicate the horizontal loading element. Fig 2-12 Evidence of soft tissue attachment between the hemispheric abutment base and oral mucosa. Seconds after removing an abutment, slight petechial bleeding occurs. This image shows the clinical appearance of the oral mucosa after removal of an abutment that was in place for 13 years.

Fig 2-11 The hemispheric abutment base plays a role in bone gain around Bicon implants. (a) Postinsertion radiograph. (b) Four-year follow-up radiograph.

element that creates a horizontal surface, which transmits compressive occlusal loads into the bone between it and the sloping shoulder (Fig 2-10).

Along with the dual roles it plays in both bone loading and as a second platform switch, the hemispheric abutment base is also an important factor in bone gain around Bicon implants[18] (Fig 2-11). In addition, there is ample anecdotal evidence to suggest the formation of a soft tissue attachment between the oral mucosa and the base. Many clinicians have remarked that shortly after removal of a seated abutment from its implant, there is slight petechial bleeding, which suggests that soft tissue attachments may have been torn (Fig 2-12).

The new Universal Abutments and their corresponding transitional abutments possess a hemispheric base with the added benefit of a single shaft length. This prevents a mis- Fig 2-13 Bone harvested through the use of slow-speed drilling.

Fig 2-14 Slow drilling does not require irrigation; this prevents important cellular and molecular factors from being washed away at the surgical site. (a) View of implant being inserted into the osteotomy with blood. (b) Implant seated in osteotomy with blood.

Fig 2-15 Eighteen-year postinsertion radiograph showing two short implants supporting long crowns.

match between the diameters and shaft lengths of transitional and definitive abutments, which could be a potential source of inflammation and bone loss, as seen with previous abutments with different shaft heights and base diameters.

Slow drilling

Although slow drilling is not a feature of the Bicon design itself, it has been a significant aspect of Driskell’s surgical protocol since 1968. The heat generated by high-speed drilling of an osteotomy can be extremely damaging to the surrounding bone.[19,20] Moreover, to compensate for the heat generated during drilling, irrigation with water is required; however, this flushes away important cellular and molecular factors involved in bone healing and decreases a clinician’s visibility. Irrigation also necessitates suction (occupying an assistant’s hand) and requires the purchase of expensive burs with internal bores—a possible source of pyrogenic contaminants. Therefore, to avoid these problems, osteotomies prepared for Bicon implants are generated using slow drilling (ie, 50 rpm).

In addition to preserving the healthy bone at the osteotomy site, there are other benefits to slow drilling. Slow drilling allows bone to be easily harvested within the flutes of reamers to be used as a grafting material (Fig 2-13). It also provides greater tactile awareness during the preparation of an osteotomy, particularly in seemingly impossible sites such as those requiring ridge splitting or sinus floor elevation. As previously mentioned, slow drilling avoids the need for irrigation, thus preserving the patient’s blood (with its important cellular and molecular factors) at the surgical site; this also results in superior osseointegration and high-quality bone[21] (Fig 2-14).

Finally, slow drilling extends the life of surgical instruments and provides for easier cleaning of the surgical reamers. This further extends their life, allowing significantly more osteotomy preparations than the more expensive internally irrigated burs. Approximately 200 osteotomies may be prepared with a Bicon reamer, significantly reducing the cost needed to replace surgical reamers or burs per osteotomy prepared.

Short length

The most striking characteristic of Bicon implants is their short length and narrow width (Fig 2-15). A short overall length allows Bicon implants to be placed in edentulous sites where there is minimal bone height and width—a common feature of such sites. The ability to place implants in areas of minimal bone height eliminates the costs and morbidity associated with bone-grafting procedures. Moreover, owing to their short length and narrow width, Bicon implants avoid extensive and expensive surgical modalities such as bone grafting and nerve repositioning, as well as complex splinted restorations with custom-made attachments[18] (Fig 2-16). Although long implants seem to function well, short implants present a much less invasive option (see Fig 2-16d).

Recommended implant guidelines can be found in chapter 8. As a brief overview, Bicon implants with a 2.0-mm well are best suited to replace mandibular incisors. Implants with a 2.5-mm well should be used for maxillary freestanding anterior restorations because their locking taper has greater resistance to displacement. Implants with a 3.0-mm well are ideal for all posterior restorations (Fig 2-17). Fig 2-16 Short implants provide exceptional versatility. A Bicon implant has been placed over a broken implant from a different manufacturer. Using a short implant eliminated the need for a more invasive procedure. (a) Preoperative radiograph showing the broken implant. (b) Postinsertion radiograph. (c) Four-month follow-up showing remarkable bone gain around the Bicon implant. (Courtesy of Dr Steven Milman, Round Rock, Texas.) (d) Radiographic view comparing a short Bicon implant and a zygomatic implant. (e) Panoramic radiograph comparing short Bicon implants and zygomatic implants. (f) Panoramic radiograph of a TRINIA prosthesis supported by short Bicon implants.

Crown-to-implant ratio (CIR) has long been used by clinicians to determine the appropriateness of a given implant/ crown combination, with unfavorable CIR seen as carrying higher risk.[22] This may cause some clinicians to pause when considering short implants; however, clinical studies have shown that increased stress as measured by increased CIR does not have a deleterious effect on peri-implant bone surrounding Bicon implants (see chapter 16). Urdaneta et al[23] reported that CIR of up to 4.95:1 had no significant effect on crestal bone levels around single-tooth Bicon implants. Birdi et al[22] evaluated 309 short Bicon implants and concluded that there was no significant relationship between CIR and crestal bone levels. Schulte et al[24] reported only 16 failures out of 889 locking-taper single-tooth implants and concluded that there was no clinically significant difference between the CIR of those implants that were in function and those implants that failed. The consensus report of the European Association of Dental Implantologists[25] states that the use of short or narrow implants can be a reliable treatment option.

Finally, placing longer, threaded implants in adolescent patients is considered inadvisable due to the continuous growth of the alveolar bone. However, because Bicon implants are ideally placed 2.0 to 3.0 mm below the crest of the alveolar bone, implants can be successfully placed in patients as young as 8 years old (Fig 2-18). (Chapter 10 provides further analysis of implant placement in adolescents.)

Narrow width

Bicon’s narrow implants make the restoration of congenitally missing maxillary lateral incisors and mandibular incisors, as well as severely atrophic alveolar ridges and fibular bone grafts, a less challenging proposition (Fig 2-19; see chapter 17). Bicon has offered 3.5-mm-diameter implants since 1985 and 3.0-mm-diameter implants since 2010. As with all other Bicon implants, the sloping shoulder enhances the preservation of scarce crestal bone, which is especially important in cases where the alveolar bone is atrophic. Even in the presence of minimal space, the narrow implants provide for natural-looking gingival aesthetics because their platforms are only 2.0 mm in diameter at the orifice of the implant well (Fig 2-20). Fig 2-18 Implant placement in adolescents. (a) Postinsertion radiograph in an adolescent patient. (b) Clinical image revealing healthy papillae. (c and d) Clinical and radiographic images 12 years after implant placement in a different adolescent patient. Fig 2-19 Narrow implants reduce the challenges of placement in atrophic ridges. (a) Preoperative radiograph illustrating the atrophic ridge ( yellow line = 3.83 mm; red line = 4.5 mm). (b) Inserting the implant. (c) Postinsertion radiograph. Fig 2-20 Narrow implants provide for natural-looking gingival aesthetics. (a) Clinical appearance 3 years after implant placement. (b) Radiograph after 3 years. Because the implant platform is only 2.0 mm in diameter at the orifice of the implant well, it supports a healthy, aesthetic papilla. Fig 2-21 Peri-implant bone gain around Bicon implants. (a) Postinsertion radiograph. (b) Seven-year follow-up radiograph. Areas of bone gain are indicated by the white arrows . (Courtesy of Robert Noone, Camp Verde, Arizona.)

Peri-implant bone gain

Another highly appealing feature of Bicon implants is their propensity for peri-implant bone gain. Peri-implant bone gain is even observed well after crown insertion (Fig 2-21). Yoo et al[26] evaluated changes in crestal bone levels adjacent to immediately loaded Bicon implants and came to the surprising conclusion that instead of bone loss, there was bone gain. Of the implants evaluated, Yoo et al[26] reported that 32.2% showed bone gain, with five implants showing bone gain greater than 2.0 mm (bone levels remained constant in the other implants and did not decrease).

In a similar study, Urdaneta et al[18] showed that 24.8% of implants demonstrated crestal bone gain 5 years after crown insertion, with significant bone gains around 5.0 × 8.0–mm implants in the mandible. The authors hypothesized that the magnitude of stress produced by masticatory forces in the posterior mandible are distributed around the implant in a manner that causes adjacent bone to be loaded at levels equal to, or higher than, the minimum effective strain necessary for bone modeling and remodeling. This resulted in positive gains in both bone density and crestal height[18] (see chapter 16).

It is entirely possible that the crestal bone stability and gain observed around Bicon implants is a biologic response to mechanical load: Wolff’s law[6] and Frost’s work[7] are certainly in agreement with such a hypothesis (see chapter 5). Even when bone loss does occur around Bicon implants— stemming from damage caused by extraneous cement, hypo-occlusion, or food impaction—it can often be reversed using the techniques discussed in chapter 6.

Using Bicon Implants

Bicon implants can be used for all conventional and guided surgery techniques; more importantly, because of their singular design, Bicon implants can be used in a wide variety of situations that would prove impossible with other implant designs.

The ideal placement of Bicon implants is 2.0 to 3.0 mm below the alveolar crest; however, they may be placed at or above the crest of the bone in certain clinical situations. They may be placed using a single-stage, two-stage, or immediate stabilization and function technique. Many experienced clinicians prefer to position implants slightly deeper for better aesthetic results when immediately placing implants or after a ridge-splitting procedure.

Basic implant procedures are discussed in detail in chapter 8. Briefly, a pilot drill is used at 1,100 rpm with or without external irrigation to prepare the initial osteotomy and establish the implant’s final position and depth (Fig 2-22a). Hand or Latch Reamers (rotating at 50 rpm) are then used without irrigation to sequentially widen the osteotomy in 0.5-mm increments to the desired implant diameter (Fig 2-22b). Using Hand Reamers or Latch Fig 2-22 (a) A pilot drill is used to initiate the osteotomy. (b) A 2.5-mm reamer is used to widen the osteotomy.

Reamers at this speed enables clinicians to harvest autogenous bone at the same time they are preparing the osteotomy. Once the osteotomy preparation is completed, the implants are passively seated without torque, which causes bone dieback, and the harvested bone is placed over the implant (see chapter 4).

Restorative Capabilities

The Bicon implant system is fully compatible with all conventional restorative techniques and materials such as gold, zirconia, and lithium disilicate. Additionally, there are restorative techniques that are only available with the Bicon system. The compatibility of the Bicon system with both conventional and specialized restorative techniques is due in large part to its innovative abutment design: a design that has evolved over the years while maintaining its locking-taper IAI and its double platform-switching hemispheric base.

Evolution of Bicon Abutments

Bicon abutments have evolved to meet changing clinical needs, restorative techniques, and materials. The original Bicon abutment possessed a 2.0-mm shaft with either a 0- or 15-degree prosthetic post; this original post size was later expanded to a diameter of 2.5 or 3.0 mm. The 3.0-mm-diameter post was introduced in 1997 as a response to potential metal fatigue concerns with 2.0-mm abutment shafts. The 2.5-mm post was implemented in 2010 to produce a tighter locking-taper connection and in-

Fig 2-23 The Brevis Abutment system offers a Fig 2-24 Fixed-Detachable Abutments have re- Fig 2-25 The original Non-Shouldered Abutment desmaller male retentive post and corresponding o-ring tained the same design since their inception. signs used for all restorations can be readily modified. attachment that offers a lower profile than cup-shaped attachments.

Fig 2-26 Stealth Abutments reduced the need for Fig 2-27 The Universal Abutment takes full advanmodifications as required for Non-Shouldered Abutments. tage of modern materials and techniques.

crease the shaft’s resistance to displacement for maxillary anterior freestanding implants.

Abutments intended for cemented removable prostheses originally consisted of a single 4.0-mm ball attached directly to a locking-taper shaft; there were also 4.0-mm ball abutments with a shoulder and a hemispheric base attached to a shaft with an angle of either 0 or 15 degrees. Abutments with magnetic attachments were also available. These initial abutments were replaced with the Brevis Abutment system in 2005, which offered a smaller male retentive post and corresponding o-ring attachment (Fig 2-23). Overall, the Brevis Abutment system offers a lower profile as well as other clinical benefits that cup-shaped abutment systems cannot provide.

While changes to materials and clinical practice have led to new abutment designs, the Fixed-Detachable Abutment, or the abutment for screw-retained prosthetics, has retained the same design since its inception (Fig 2-24). In addition to standard Bicon features, the Fixed-Detachable Abutment possesses a 25-degree cone with a hemispheric base attached to either a 0- or 15-degree shaft and a four-threaded bore for a prosthetic retention screw. Having a retention screw with only four threads offers the clinician the ability to readily determine if a prosthesis is fitting passively (ie, if the retention screw head is flush with the conical abutment, then the prosthesis is fitting passively). The 25-degree conical abutment head eliminates the possibility for any adverse lateral loading of the retention screw.

The original abutment design for all fixed, cemented, and telescopic restorations was the Non-Shouldered Abutment, essentially a replica of a prosthetically prepared natural tooth (Fig 2-25). The Non-Shouldered Abutment frequently required modification to accommodate restorations; to facilitate this, the Stealth line of Shouldered Abutments was introduced in 2000 (Fig 2-26). Nevertheless, with the advent of the new, revolutionary, and eminently successful polyceramic or nanoceramic indirect composite materials, along with digital imaging, computer-aided design/computer-assisted manufacturing (CAD/CAM) techniques, and their associated materials (eg, TRINIA, a fiber-reinforced resin CAD/CAM material), it was apparent that a different abutment design was necessary.

In 2014, a new abutment system was introduced that maximized the efficiencies provided by new materials and techniques: the Universal Abutment (Fig 2-27). The geometric design of the Universal Abutment provides for en- Fig 2-28 Prefabricated titanium copings for telescopic TRINIA prosthetics are available as red retentive and metallic nonretentive copings. (a) A telescopic TRINIA prosthesis. (b) Highly retentive and easy-release coping styles.

Fig 2-29 White Scanning Posts make virtual implant-level transfer impressions possible using intraoral digital imaging devices. Fig 2-30 The Bicon system can accommodate crowns as much as five times longer than the implant.

Fig 2-31 Abutments with 0, 10, 15, and 25 degrees of angulation allow the paralleling of abutments with nonparallel implants. (a) Guide pins illustrate nonparalleled placement of implants. (b) An angled abutment is inserted. (c) Clinical appearance of the paralleled abutments.

hanced digital imaging without sacrificing the ability to be replicated and restored with conventional impression materials and techniques. The Universal Abutment also requires minimal reduction or modification to accommodate the greater space requirements of the newer polyceramic indirect composites and CAD/CAM materials, and its parallel sides facilitate telescoping restorations. Furthermore, different hemispheric base heights with angulations of 0 or 10 degrees can accommodate a variety of clinical situations.

In addition to the various prosthetic components associated with the Universal Abutment, prefabricated titanium retentive copings were also offered, making the fabrication of telescopic prosthetics a more cost-effective and convenient proposition (Fig 2-28). White Scanning Posts were also introduced in 2015 to make virtual implant-level transfer impressions possible using intraoral digital imaging devices (Fig 2-29). Because of the significant improvements in its clinical and laboratory capabilities, the new Universal Abutment will soon become the abutment of choice.

Unique Capabilities

The Bicon system can accommodate crowns as much as five times longer than the implant, even for single freestanding restorations (Fig 2-30). Moreover, abutments with 0, 10, 15, and 25 degrees of angulation allow the paralleling of abutments with nonparallel implants; these facts taken together provide for infinite restorative possibilities (Fig 2-31). Although the Bicon implant can be restored with all conventional restorative techniques and materials (eg, gold, zirconia, and lithium disilicate), the following section demonstrates the restorative capabilities and procedures that are only practical or possible with Bicon implants:

• Porcelain fused to metal

• Integrated Abutment Crowns (IACs)

• Intraoral bonding of partial dentures or pontics

• Extraoral cementation

• Insertion of fixed partial dentures and splinted restorations Fig 2-32 IACs allow the use of small prosthetic posts. (a and b) Clinical and radiographic images depicting minimal prosthetic metal support. (c) A 5-year follow-up radiograph showing that a short implant can support a large molar prosthesis. Fig 2-33 The seamless interface between the abutment and crown of an IAC promotes gingival health. (a) IAC restorations on the day of insertion revealing metal margin and insufficient papillae. (b) The health of the mucosa and papillae is considerably improved in only 3 weeks.

• Telescopic prostheses without primary castings, using prefabricated retentive copings

• Minimal-size prosthetic posts

• CAD/CAM fixed prosthetics

• IAC and TRINIA maintenance

Porcelain fused to metal

Clinicians familiar with post-and-core restorations will find similarities when restoring a Bicon implant. An abutment with the largest hemispheric base that supports the papillae without encroaching upon them is selected to fit the edentulous space and can be modified as desired using carbide burs. A digital impression or a regular closed-tray impression, similar to what is used for natural teeth, is made and followed by an intraoral crown cementation. Alternatively, an implant-level or abutment-level transfer impression can be made in the conventional manner or by digital scanning, enabling the technician to select the appropriate abutment and fabricate the crown. Because of the 360 degrees of universal abutment positioning, crowns can also be cemented extraorally, eliminating the issues associated with extraneous cement.

Integrated Abutment Crowns

The revolutionary cementless and screwless IAC is the ideal telescopic crown, providing excellent aesthetics.[27] IACs provide the opportunity to use prosthetic posts as small as 4.0 × 2.0 mm (Fig 2-32).[28,29] Thus, because of its short trajectory, each abutment is more universal in its use; however, excessive thicknesses over 5.0 mm should have a TRINIA core, thereby eliminating many aesthetic and technical issues inherent with screw-retained abutments and with materials that require maximum metallic support. Additionally, the seamless interface between the titanium abutment and the polished polyceramic crown—so well fabricated it is undetectable by scanning electron microscope—allows papillae to return to clinical health in as little as 3 weeks (Fig 2-33).

After an implant-level impression is made or an intraoral digital scanning is performed, an IAC is fabricated in the laboratory by chemically and mechanically bonding a nanoceramic or polyceramic indirect composite material to the titanium surface of an abutment. Alternatively, a CAD/ CAM-fabricated restoration can be bonded to an abutment alone or in combination with an indirect composite. The abutment must have the widest titanium hemispheric base to support the interdental papillae without encroaching upon them. Polyceramic materials in close proximity to bone have been shown to be associated with bone loss, whereas the titanium hemispheric abutment base has been associated with bone gain (see chapter 16). Fig 2-34 IACs allow metal margins to be easily concealed. (a) A metal margin is revealed upon insertion. (b) Polyceramic is added to the IAC. (c) The IAC is polished. (d) The IAC is reinserted. (e) Final appearance.

IACs give the clinician the ability to easily conceal metal margins and clinical crown length discrepancies at the initial insertion or even years later. After adjusting the metal margin with a bur, primer is applied to the titanium abutment prior to its being opaqued. A polyceramic material is then added, light cured, and polished (Fig 2-34).

Another benefit of the IAC is the ease with which intraoral closure of open interproximal or occlusal contacts can be carried out: This is achieved by roughening and cleaning the surface with ethyl alcohol before applying modeling liquid, then adding and light curing the necessary polyceramic material to correct the deficient interproximal or occlusal contact, and finally polishing (Fig 2-35).

Intraoral bonding of partial dentures or pontics

Intraoral bonding of partial dentures or pontics is reliably achieved with IACs by roughening and applying modeling liquid to the interproximal surface of adjacent polyceramic surfaces. After polyceramic material is added to all, they are definitively positioned, and the added material is then light cured and polished.

Extraoral cementation

A crown can be cemented to a Bicon abutment extraorally because of its 360 degrees of universal positioning. After the removal of any extraneous cement, the cemented prosthetic unit can be inserted into the well of the implant. The ability to do this essentially affords the clinician the opportunity to fabricate an IAC chairside using CAD/CAM materials.

Inserting fixed partial dentures and splinted restorations

Bicon’s locking-taper IAI allows abutments to be rotated 360 degrees in the well of the implant; this positioning is especially advantageous when seating multiple abutments, such as those for a fixed partial denture or splinted restoration. Clinicians can use the definitive prosthesis or a seating jig to orient and seat abutments into their respective wells at the same time, even when their implants are not parallel (Fig 2-36). Fig 2-35 IACs allow the easy intraoral closure of open interproximal or occlusal contacts. (a) The IAC is removed and its surface is roughened. (b) The interproximal contact is adjusted. (c) The IAC is retried. (d) Light curing the newly added material. (e) Final clinical appearance. Fig 2-36 Fixed partial denture and splinted restorations can be easily inserted owing to Bicon’s locking-taper IAI. Here a seating jig is used to orient and seat the abutments into their respective wells. Fig 2-37 TRINIA is a CAD/CAM fiber-reinforced resin material recommended for partial and full-arch fixed prosthetics. TRINIA is available in two colors: pink (a) , and white (b) . (c) Five-year follow-up clinical appearance of TRINIA. (d) Five-year follow-up radiograph showing the four short implants supporting the TRINIA prosthesis. Fig 2-38 Relining TRINIA is easy and cost-effective and can be achieved chairside. (a) TRINIA relining materials. (b) The material is added to the TRINIA extraorally. (c) The modified TRINIA prosthesis is reinserted, and excess material is removed. (d) Light curing the material intraorally. Fig 2-39 (a) An air-abrasion device can be used extraorally to remove heavy stains on IACs or TRINIA restorations. (b) A bristle brush with diamond paste can be used intraorally to remove heavy stains on an IAC.

Telescopic prostheses without primary castings

Because the solid 0-, 10-, 15-, and 25-degree abutments are screwless and have 360 degrees of universal positioning, the parallelism required for telescopic restorations can be easily achieved (see Fig 2-28). Furthermore, because the abutments themselves can be milled or modified, there is no need for primary castings.

Minimal-size prosthetic post

Unlike metal-ceramic crowns, polyceramic or nanoceramic materials require minimal metal support; therefore, fewer abutment sizes are required because smaller abutments are more universal in their use.[28] Furthermore, less-than-ideal implant placements and trajectories are easier to restore aesthetically with smaller prosthetic abutment posts (see Fig 2-31).

CAD/CAM fixed prosthetics

The advent of CAD/CAM is revolutionizing dentistry. When used in conjunction with the Bicon system, CAD/CAM can provide superior restorations that are also very cost-effective. The CAD/CAM fiber-reinforced resin material TRINIA

is recommended for any restoration that was previously restored with metal (Fig 2-37). For example, TRINIA’s nonanatomical bar substructures can be used with composite resin denture teeth, a more cost-effective modality compared with handcrafted polyceramic teeth.

Relining TRINIA prostheses can be achieved quickly and easily chairside and in a cost-effective manner, making this material convenient for both clinician and patient alike. An effective chairside relining procedure is accomplished in a few easy steps. After extraorally cleaning the ridge side of the prosthesis, an appropriate bonding liquid is applied. Next, a sufficient amount of polyceramic material is applied in 2.0-mm increments to the prosthesis to occlude the gap between it and the alveolar ridge. Once the material is intraorally adapted, any excess material is removed and light cured. The TRINIA prosthesis is then removed for further light curing and polishing (Fig 2-38).

IAC and TRINIA maintenance

Any staining or breakage of an IAC polyceramic hybrid material can be easily rectified. Heavy stains on either an IAC or TRINIA prosthesis can be removed intraorally or extraorally using Sympro (Renfert) cleaning devices, air-abrasion devices, or simply by using a diamond polishing paste with a bristle brush (Fig 2-39). Changes to contour and shading that occur over time can also be easily rectified, either intraorally or extraorally.

References

1. Driskell TD, Heller AL. Clinical use of aluminum oxide endosseous implants. J Oral Implantol 1977;7:53–76.

2. Hahn J. Clinical experience with the Titanodont subcortical implant system. J Oral Implantol 1983;11:72–88.

3. Bothe RT, Beaton KE, Davenport HA. Reaction of bone to multiple metallic implants. Surg Gynecol Obstet 1940;71:598–602.

4. Leventhal GS. Titanium, a metal for surgery. J Bone Joint Surg Am 1951;33A:473–474.

5. Driskell TD. DB Precision Implant System. Vol K853788 (1985). http://www. accessdata.fda.gov/scripts/cdrh/cfdocs/cfPMN/pmn.cfm?ID=K853788. Accessed 26 January 2017.

6. Wolff J. Das Gesetz Der Transformation Der Knochen. Berlin: Verlag von August Hirschwald, 1892.

7. Frost HM. The mechanostat: A proposed pathogenic mechanism of osteoporoses and the bone mass effects of mechanical and nonmechanical agents. Bone Miner 1987;2:73–85.

8. Huang B, Meng H, Zhu W, Witek L, Tovar N, Coelho PG. Influence of placement depth on bone remodeling around tapered internal connection implants: A histologic study in dogs. Clin Oral Implants Res 2015;26:942–949.

9. Coelho PG, Marin C, Granato R, Suzuki M. Histomorphologic analysis of 30 plateau root form implants retrieved after 8 to 13 years in function. A human retrieval study. J Biomed Mater Res B Appl Biomater 2009;91:975–979.

10. Marin C, Granato R, Suzuki M, Gil JN, Janal MN, Coelho PG. Histomorphologic and histomorphometric evaluation of various endosseous implant healing chamber configurations at early implantation times: A study in dogs. Clin Oral Implants Res 2010;21:577–583.

11. Bozkaya D, Müftü S, Müftü A. Evaluation of load transfer characteristics of five different implants in compact bone at different load levels by finite elements analysis. J Prosthet Dent 2004;92:523–530.

12. Chou HY, Müftü S, Bozkaya D. Combined effects of implant insertion depth and alveolar bone quality on periimplant bone strain induced by a wide-diameter, short implant and a narrow-diameter, long implant. J Prosthet Dent 2010;104:293–300.

13. Urdaneta RA, Seemann R, Dragan IF, Lubelski W, Leary J, Chuang SK. A retrospective radiographic study on the effect of natural tooth-implant proximity and an introduction to the concept of a bone-loading platform switch. Int J Oral Maxillofac Implants 2014;29:1412–1424.

14. Lazzara RJ, Porter SS. Platform switching: A new concept in implant dentistry for controlling postrestorative crestal bone levels. Int J Periodontics Restorative Dent 2006;26:9–17.

15. Dibart S, Warbington M, Su MF, Skobe Z. In vitro evaluation of the implant-abutment bacterial seal: The locking taper system. Int J Oral Maxillofac Implants 2005;20:732–737.

16. Keating K. Connecting abutments to dental implants: An engineer’s perspective. Ir Dent 2001:43–46.

17. Di Carlo F, Marincola M, Quaranta A, Bedini R, Pecci R. Micro-Tac analysis on implants with a locking taper connection. Dent Cadmos 2008;3:55–60.

18. Urdaneta RA, Daher S, Leary J, Emanuel K, Chuang SK. Factors associated with crestal bone gain on single-tooth locking-taper implants: The effect of nonsteroidal anti-inflammatory drugs. Int J Oral Maxillofac Implants 2011;26:1063–1078.

19. Sharawy M, Misch CE, Weller N, Tehemar S. Heat generation during implant drilling: The significance of motor speed. J Oral Maxillofac Surg 2002;60:1160–1169.

20. Kim SJ, Yoo J, Kim YS, Shin SW. Temperature change in pig rib bone during implant site preparation by low-speed drilling. J Appl Oral Sci 2010;18:522–527.

21. Coelho PG, Suzuki M, Guimaraes MVM, et al. Early bone healing around different implant bulk designs and surgical techniques: A study in dogs. Clin Implant Dent Relat Res 2009;12:202–208.

22. Birdi H, Schulte J, Kovacs A, Weed M, Chuang SK. Crown-to-implant ratios of short-length implants. J Oral Implantol 2010;36:425–433.

23. Urdaneta RA, Rodriguez S, McNeil DC, Weed M, Chuang SK. The effect of increased crown-to-implant ratio on single-tooth locking-taper implants. Int J Oral Maxillofac Implants 2010;25:729–743.

24. Schulte J, Flores AM, Weed M. Crown-to-implant ratios of single tooth implant-supported restorations. J Prosthet Dent 2007;98:1–5.

25. Neugebauer J. Recommendations for short, angulated, or diameter-reduced implants. Eur J Dent Implantol 2016;12:16.

26. Yoo RH, Chuang SK, Erakat MS, Weed M, Dodson TB. Changes in crestal bone levels for immediately loaded implants. Int J Oral Maxillofac Implants 2006;21:253–261.

27. Urdaneta RA, Marincola M, Weed M, Chuang SK. A screwless and cementless technique for the restoration of single-tooth implants: A retrospective cohort study. J Prosthodont 2008;17:562–571.

28. Silva NRFA, Bonfante EA, Rafferty BT, et al. Modified Y-TZP core design improves all-ceramic crown reliability. J Dent Res 2011;90:104–108.

29. Bonfante EA, Suzuki M, Lubelski W, Silva N, Coelho PG. Reliability of abutments veneered with indirect composite for implant-supported crowns [Proceedings of the IADR General Session 2010]. Barcelona: International Association for Dental Research, 2010.

Modified from Morgan VJ. Short and narrow plateaued implants. In: Ewers R, Lambrecht JT (eds). Oral Implants: Bioactivating Concepts. Chicago: Quintessence, 2013.

03

Characteristics of Implant-Abutment Prosthetic Systems: A Paradigm Shift

Estevam A. Bonfante | Marcelo Suzuki | Gerson Bonfante | Ronaldo Hirata | Ernesto Byron Benalcazar Jalkh | Adolfo Coelho de Oliveira Lopes | Vinicius P. Fardin | Paulo G. Coelho

Because it is acknowledged that implant systems can achieve and maintain osseointegration and be restored with more or less maintenance over the long term, efforts have recently been focused on decreasing or even eliminating the treatment time frame from implant placement to prosthetic loading.[1] Dental implant treatments, from the bone response as a function of implant macrogeometry (hardware design) and surgical techniques, to final restorative decisions, hold more complexity than is commonly acknowledged.[2] Despite the fact that significantly higher survival rates combined with lower complication rates for implants have been reported in published studies from the year 2000 to date (suggesting an enthusiastic learning curve in implant dentistry), there are still common incidences of aesthetic, biologic, and technical complications.[3] This recent observation, reported in most implant dentistry literature, unequivocally indicates that the industry’s research and development departments will—aside from investing in improving osseointegration—also focus on improving the reliability (ie, probability of survival) of their systems so that they can be more predictable in the future.[3]

It has always been commonplace for implant companies to periodically redesign their systems in an attempt to reach such goals; however, the most important features of the Bicon implant (its hardware design, the tapered-interference fit [ie, locking-taper] abutment design, and the sloping shoulder) have been virtually unchanged since 1985. Although the Bicon system continues its innovation with changes to new restorative materials and techniques (the most recent being prefabricated retentive copings for TRINIA telescopic prosthetics), this chapter elaborates on the rationale for this conservative approach regarding the overall design of the Bicon system. The authors present and discuss data on a variety of prosthetic solutions encompassing prosthodontic aspects such as the implant-abutment connection; the reduced number of restorative parts used to reach the same aesthetic and functional results as other systems; and how the restorative technique for implants, abutments, and prostheses ultimately affects their survivability.

Implant Hardware and Prostheses

Although dental implants have been successfully used during the past few decades, recent research has shown that multiple factors affect osseointegration and that the implant’s geometric design plays a key role in the bone healing.[2,4]

It is paramount for the restorative clinician to understand that bone healing around Bicon’s implant design follows a completely different pathway than in other implant designs, both in the short and long term. This is because of the presence of spaces, often called healing chambers , that exist between the walls of the osteotomy and the core of the implant.

On the other hand, threaded or screw-root form (SRF) implants are torqued (ie, screwed) into the bone, creating a tight, intimate contact with the bony walls of their osteotomy; there is no space for a healing chamber. In addition, during the formation of the osteotomy for a threaded implant, the bone is compressed and there is actually an initial period of bone die back. During this period of die back, as well as in the beginning of the process of osseointegration, there is a delay in initial healing. When the die back is complete, the bone begins to recover. As it does, a lamellar, interstitial type of bone is laid down around the implant on the walls of the osteotomy and subsequently at the site of interfacial bone remodeling.[5–7] This type of lamellar bone is also called appositional bone . Only in healing chambers will bone evolve toward the formation of cortical-like Haversian bone around the implant, a kind of bone with positive mechanical properties that, over time, continue to improve in quality. Even after 5 years, regardless of the osteotomy’s initial bone type, this fact was consistently shown in human retrieval studies.[8–10]

The restorative dentist must bear in mind that the bony foundation of the Bicon prosthesis is different in three main aspects. First, for implants with a similar diameter and length, the final area of bone in contact with the implant varies substantially as a function of the implant’s design. The presence of healing chambers significantly increases the area of contact. Second, at the crestal aspect of the implant, a sloping shoulder with a narrow cross-sectional design effectively reduces and transfers increased occlusal loads that could otherwise lead to crestal bone loss; this is not possible in implants with a wider cervical profile. Third, whether a prosthesis is installed in the maxillary or mandibular arch, in the anterior or posterior region, or on implants with or without surface treatments, the mechanical properties of human bone (ie, elastic modulus and hardness in the sense of flexural strength, tensile strength, and compressive strength) supporting the implants and prostheses will increase in quality during the first 5 years following implantation and function, and that improvement will be retained thereafter.[10,11]

It is critical that conscientious clinicians grasp how fundamental differences in implant design will impact their restorative decisions. The plateau design creates healing chambers; the healing chambers create an essentially stronger and harder (cortical-like Haversian) bone. When that advantage is combined with a sloping shoulder design to transfer the forces of increased occlusal loads, the result is a rationale for the successful use of short implants and the increased crown-to-implant ratio (CIR) that follows. The clinician’s options are significantly expanded.

The principles and limitations that govern the use of screw-in or threaded implants do not apply to the plateau design of the Bicon implant system. Additionally, several elements of the restored implant-abutment system deserve further elaboration, because they will also affect clinical understanding and success.

Implant Material and Long-Term Performance

Historically, the most commonly used dental implant material was grade 2 commercially pure titanium (CpTi); however, for a variety of reasons, including the quest for improved mechanical performance to increase the probability of survival, the use of other titanium compositions (CpTi grade 4) or alloying of titanium (eg, Ti-6Al-4V) became popular as an implant material.[12] The reason for this change is based on the higher mechanical properties of Ti alloys, such as Ti-6Al-4V, compared with grade 4 and grade 2 CpTi. Because of solution and strain hardening, grade 4 Ti has higher fatigue strength compared with grade 2 CpTi, and the fatigue strength of Ti-6Al-4V is substantially higher than both grades 2 and 4. Therefore, the preferred alloy is Ti-6Al-4V owing to its low density, an elastic modulus that is half that of cobalt-chrome or stainless steel, and its adequate fatigue and biocompatibility properties.[13,14] Fortunately, implant fractures are rare, but they have been reported in several clinical studies where CpTi grade 2 was used.[15–17] Considering the increase in life expectancy and the fact that fatigue is a cumulative process for metallic biomaterials, it is desirable for an implant material to have high mechanical properties.[18,19]

Although Ti-6Al-4V is known to be superior in mechanical properties to CpTi, only recently has research involving anatomically relevant implant-supported restorations shown that their probability of survival is higher under fatigue with Ti-6Al-4V.[20,21]

Implant-Abutment Interface Designs

A wide variety of implant-abutment interface (IAI) designs are available on the market. The three most common IAI designs can be classified as follows: screw-retained, taperintegrated screw (TIS), and Morse taper (see chapter 5).

Screw-retained

The screw-retained IAI represents the scenario in which the reliability of the bolted joint depends mainly on the abutment screw and the fit between the connecting parts. The external hexagon is the main representative of this category, and it has the highest chairside maintenance of all abutment connections because abutment screws may loosen or fracture. The need for maintenance may also be exacerbated by an inadequate screw preload, a misfit of the mating components, or the rotational properties of the screws.

Research and improvements on the screw-retained IAI have been centered on and limited to alterations in the mechanical or tribologic (ie, principles of friction, lubrication, and wear) properties of the abutment screw (eg, diamond-like carbon coating or changes in screw material). Additionally, reevaluating current knowledge (eg, systematic reviews and technical complications such as the incidence of abutment screws loosening in external connection types) has been a focus for screw-retained IAI.[22,23] The external hexagon has been replicated in several implant systems since the introduction of the Brånemark implant. Despite the implant’s lack of a sound biomechanical rationale, the external hexagon provides an antirotational system as well as ways to carry and position the implant.[24]

Tapered integrated screw

The TIS is secured by frictional forces on both the screw threads and on the tapered section, where the contact area and the forces on the tapered section are tailored by their design. Compared with the screw-retained IAI, TIS abutments present fewer cases of screw loosening or fracture. The tapered section provides a sort of interference fit with the implant and a superior resistance to bending, as it shields the abutment screw.[25,26] Surprisingly, implant systems with TIS abutment interface have been erroneously coded as having a Morse-taper IAI, despite possessing tapers as large as 11 degrees (see chapter 5). Morse tapers with a taper angle less than 7 degrees are self-locking, which negates the function of the screw threads.[27] In addition, because of the larger angle of some of these TIS systems, they cannot be considered self-locking Morse tapers (a more accurate name for such TIS systems should be internal conical connection ); this type of connection would not remain safely secured without their retaining abutment screws because they do not cold-weld under the conditions in which they are commonly engineered to be used.[24] However, there is a consensus that the TIS IAI results in a significant reduction of complication rates when compared with the pure screw-retained IAI.

Unfortunately, the TIS IAI design still requires a space between the abutment and implant to enable the seating of the abutment in the implant well or hexagon. This space of varied dimensions results in a two-way path for fluid leakage and bacterial penetration at the IAI, regardless of loading conditions (see chapter 6).[28–33]

Although hexagonal platforms and TIS systems offer a small amount of protection against bacterial infiltration, the gap between components nevertheless allows for contamination, potentially compromising peri-implant soft and hard tissues.[34–36]

Morse taper

Systems that use a locking-taper connection use a type of Morse taper to secure the abutment to the implant without the use of internal screws. The classic example of a pure locking-taper design is found in the Bicon system, which has had a 1.5-degree taper angle since its inception in 1985 (see chapter 5). The tapered surface of the abutment creates a large frictional resistance area in the matrix well of the implant (ie, IAI) where the locking-taper connection provides the required forces for frictional retention; cold-welding at the IAI in turn creates a bacterial seal at the IAI.[37,38] Furthermore, to maintain clinical consistency in the aforementioned features, all components must be interchangeable, regardless of their manufacture date. The production of purely locking-taper connections requires not only highly sophisticated machining tools but also meticulous attention to manufacturing protocols.

From a clinical standpoint, there are substantial differences when working with a locking-taper system compared with screw-retained or TIS systems, especially where the prosthesis is concerned. Such differences include the efficient insertion and removal mechanisms and lack of abutment indexing, a feature that allows for 360 degrees of universal positioning of the abutment or prosthesis. The differences between a locking-taper system and more conventional screw-retained and TIS systems are often a source of unsubstantiated claims; this can lead to misconceptions regarding the clinical use of the locking-taper system.

It is essential to first note that the placement of the prosthesis does not require a sharp blow, as suggested by detractors of the implant. For instance in the posterior region, the seating of an abutment can be guided by occlusion, and because the definitive seating in this region occurs mostly in a vertical direction to the implant, posterior crowns almost never become loose once they have been properly seated.

Insertion in the maxillary anterior region does require a few gentle taps; however, these are not sharp blows as some have suggested. Given that seating forces must occur in an oblique orientation, and not necessarily in line with the incisal edge, a silicone custom-seating jig is used to direct the seating forces through the long axis of the abutment and implant well. To remove the abutment, it may be necessary to gently grasp and tap it with extraction forceps while protecting the crown material with rubber dam or gauze. Alternatively, gently tapping on the handle of the grasping forceps is also an effective means of removing an abutment, especially if the implant was only recently integrated. Concerns about complications such as loss of osseointegration during the removal of an abutment or prosthesis, or about the inability to retrieve a restoration, are unfounded.

Table 3-1 Characteristic strength of several IAI designs for screw-retained, TIS, and locking-taper systems EH, external hexagon; IH, internal hexagon; IC, internal conical; RN, resin nanoceramic; MC, metal ceramic; NA, not applicable.

Another notable difference in locking-taper systems is the 360 degrees of abutment positioning, which results not only in flexibility, but also in the unmatched simplification of surgical and prosthetic procedures.[27] Another significant clinical benefit is the ease with which a fixed prosthesis may be removed. Unlike with screw-retained abutments, the retrievability of fixed prostheses is straightforward and accomplished by either removing the cemented prostheses or removing abutments from the wells of the implants, as described above. A robust clinical database is readily available and well documented for the Bicon system. At least 4 years of retrospective analysis of 1,757 functioning implants with locking-taper abutments reported minimal maintenance problems and an overall complication rate (fracture and loosening) of 2.2%.[39]

• The loosening of abutment screws is the most frequently reported technical complication, and this results in additional chairside time and expense for corrective treatments. Such complications are inherent to screw-retained and TIS systems.

• The TIS design has a hollow abutment to allow for screw passage and torque. After a restoration with a hollow abutment is installed, the hollow abutment loses its characteristic strength, unlike the solid abutments in a locking-taper system. Even if one considers the same materials and geometries, the absence of titanium in the center of the abutment significantly decreases the overall strength of the system.

• Increased mechanical properties can be expected with the Bicon system (as discussed below), considering that both implant and abutment bulk materials are composed of Ti-6Al-4V.

IAI summary

When a holistic comparison of the three most common IAI designs is made, the relevant clinical and biomechanical properties emerge and can be summarized as follows:

Table 3-1 presents the characteristic strength of several IAI designs within the three common categories.[40–48] A clear difference is observed between screw-retained and TIS systems when compared with the locking-taper system. The twofold

Table 3-2 Bilateral maximum human voluntary bite forces from several studies

increase in characteristic strength observed for the locking taper, compared with the other two implant-abutment connection types, has an important implication for prosthetic materials evaluation. Because the former two types present implant-abutment components failure at loads below those found for the prosthetic materials themselves, new materials for implants can be better evaluated from a fatigue and mechanical perspective with a purely locking-taper system. Note the shift in failure modes between the screw-type implant-abutment connections and the purely locking-taper connection.

For comparative purposes, voluntary human bite forces are presented in Table 3-2.[49–54] Note that values are commonly above the characteristic strength of both screwretained and TIS designs as presented in Table 3-1.

In-depth studies on the mechanical properties of the locking-taper interface have been carried out for the Bicon system.[11,37,55] The studies were tailored to the Bicon system; therefore, the results of these studies should not be extrapolated to any other locking-taper system, either with or without an indexing system, or with internal conical connections that are part of the TIS design.

Restorative Options for the Bicon System

All conventional restorative techniques can be used with the Bicon system; however, there are several prosthetic options that are only possible because of Bicon’s lockingtaper IAI (Fig 3-1).[56]

Ceramic and titanium

The restorative materials available with the Bicon system include all-ceramic and ceramic-like materials suitable for implant dentistry; furthermore, most if not all materials may be fabricated on a completely digital workflow. Resin-matrix ceramic materials are classified by the American Dental Association as a porcelain/ceramic and defined as “pressed, fired, polished or milled materials containing predominantly inorganic refractory compounds—including porcelains, glasses, ceramics and glass ceramics.”[57] The presence of a resin-matrix in a predominantly (ie, > 50% wt) porcelain/ceramic composition corroborates the proposed nomenclature for this material.[56]

As previously mentioned, implant and abutment bulk materials composed of Ti-6Al-4V may present improved mechanical abilities and allow them to function longer compared with grades 2 and 4 Ti. Although the TIS system is not as commonly paired with a screw-retained prosthesis as it is with a cemented one, it still seems to have an influence on the mechanical and biologic outcomes of the prosthesis.[42,58,59] By understanding the mechanical performance differences between screw-retained and cemented restorations, one can subsequently recognize the unique characteristics of restorations that are cemented on locking-taper abutments—particularly those of the Bicon Integrated Abutment Crowns (IACs).

Screw- vs cement-retained prostheses

Even though it is a topic of dispute and controversy, recent evidence shows a clear trend in fewer technical complications for cemented prostheses relative to screwretained prostheses.[60] Loosening of either the abutment or restoration screw has been commonly reported in screwretained single crowns, whereas abutment screw fractures have been reported more often in cemented crowns.[60] The 5-year survival rate for cemented fixed partial dentures (96.9%) is similar to the rate for the screw-retained partial dentures (98%), whereas the survival rate for cemented fixed full-arch prostheses (100%) exceeds the rate for screw-retained full-arch prostheses (95.8%).[60] Whether there are two screws (one for the abutment and one for the restoration) or just one to retain the abutment with a cemented prosthesis, the presence of screws increases the incidence of failure. Numerous studies, examining a wide variety of conditions, have consistently found a lower probability of survival for screw-retained restorations than for cemented restorations.[40–45,58,61–64]

Bicon’s locking taper

Because of the locking-taper IAI design, the main source of complication in implant prosthodontics (ie, loose abutment screws or fracturing) is eliminated; moreover, the overall amount of technical failures should likewise be reduced, given the reduced number of restorative components. The simplest strategy for reducing the number of restorative components is achieved when an indirect restorative material is directly bonded to an abutment: this is the concept of the IAC.[65] Mechanical and chemical surface treatment of the Ti-6Al-4V abutment makes it possible to obtain the excellent bonding strength of a highly filled indirect resin composite.[66] Similar to the computer-aided design/ computer-assisted manufacturing (CAD/CAM) technique, with its broad range of initial materials, the adhesive bonding of milled prostheses to locking-taper abutments effectively results in a one-piece screwless restoration, which is an ideal telescopic restoration.

Reducing the number of components in the lockingtaper system results in an inversely proportional fracture strength and fatigue endurance, as observed via mechanical testing.[46,47,67] Fracture strength or fatigue testing in any pure screw-retained or TIS abutment shows a consistent trend of failures in the abutment or prosthetic screws prior to failures in the crown material, regardless of the crown’s composition of metal-ceramic, all-ceramic, or ceramic-like materials.

Location

When considering an implant-supported prosthesis, it is important to bear in mind that the performance of materials usually differs in the anterior regions relative to posterior regions of the arch; failure rates generally increase in restorations toward the posterior region.[15,68] It is also crucial to note that the type of support (ie, tooth, implant, or combination of tooth and implant) makes clinical outcomes for the definitive prostheses incomparable, even for prostheses of the same material. Complications for each type of support differ as a function of the nature of their support.[69]

Metal-ceramic, zirconia-veneered, and porcelain

Choosing the prosthetic material is a challenging task, and most research since 1962 has focused on metal ceramics[70] (Fig 3-2).

In a systematic review including 17 studies for metal ceramics, and only two for all-ceramic materials used for crowns, the estimated survival rate after 5 years was the same for both materials (95.8%). A recent 10-year retrospective clinical study reported a prosthetic success rate of 70.8% for implant-supported fixed partial dentures, with the most frequent complication being the fracturing of the metal-ceramic prostheses (20.31%), followed by occlusal screw loosening (2.6%) and loss of retention (2.06%).[71] Clinical evaluations concerning patient- and implantspecific triggers of failure have shown that metal-ceramic fixed partial dentures, when opposing another metalceramic implant-supported restoration rather than a natural tooth, have a much higher likelihood of porcelain fractures requiring repair or replacement (13 times more likely).[72]

There have been recent studies specific to zirconiaveneered restorations that contradict older studies concerning the fracture of porcelain veneers, which was previously a major concern[73] (Table 3-3).[74–77] Fortunately, industry and engineering efforts have elucidated most of the issues related to zirconia-veneered restorations. Although results are promising, clinical outcomes still vary substantially between studies and are commonly based on a limited number of patients and follow-up times. For example, when comparing zirconia- e

Fig 3-2 Bicon implant placed following orthodontic treatment. (a) Postplacement radiograph showing implant in location of the second molar. (b) Clinical appearance. Note the extensive vertical bone loss and limitation of implant length dimensions. (c) Clinical appearance at stagetwo surgery. (d) Abutment installation for impression taking. (e) A metal-ceramic crown was fabricated for the definitive prosthesis. (f) Buccal view of the crown after delivery. (g) Occlusal view after delivery. (h) Follow-up radiograph shows bone level stability and a disproportionate CIR that is clinically valid for this implant macrogeometry and has well-described risk factors. veneered implant-supported crowns to metal ceramics, some studies show no significant differences in survival rates, whereas other studies show a significantly higher rate for chipping of the veneer in the zirconia-veneered restorations.[78]

It is still unclear if clinical outcomes for technical failures are similar between tooth-supported and implantsupported zirconia-veneered fixed partial dentures, or if they are significantly higher in the latter.[79] A more recent 5-year clinical follow-up of zirconia-veneered single crowns and fixed partial dentures showed 42.8% and 62% of chipping complications, respectively.[77] A comprehensive review on yttria-tetragonal zirconia polycrystal (Y-TZP) for implant prosthodontics concluded that long-term clinical evidence is missing, especially for extensive implant-supported restorations.[80] Just as the zirconia framework does not usually experience failures, fractures of the porcelain veneer will likely be less frequent in future clinical studies as the learning curve of handling and processing the material matures. With limited long-term follow-up, alternatives involve the use of monolithic zirconia restorations, even for full-arch implant-supported restorations.[81] In addition, although monolithic zirconia for full-arch restorations is perceived as Clinical studies available for porcelainfused-to-zirconia implant-supported crowns and the percentage of porcelain fractures

Table 3-3

*Note the disparity in failure rates observed at relatively short clinical service. Success rates are primarily hampered by porcelain veneer cohesive fractures.

indestructible, a 1-year follow-up showed an 88% prosthesis survival rate because of a monolithic prosthesis fracture.[82] In such scenarios, long-term wear of opposing dentition and concerns regarding low-temperature degradation of Fig 3-3 Contour plot showing characteristic strength vs Weibull modulus in fatigue of several materials used as molar IACs. Black contour , metal ceramic (reference group); red contour , CAD/CAM resin nanoceramic; blue contour , glass-ceramic in a resin-matrix; dotted contour , conventional IACs layered with Ceramage (Shofu). The dashed contour presents the highest Weibull modulus and same characteristic strength as a resin nanoceramic. This results in the same range of strength and modulus as its full-contour intact counterpart, therefore providing support to strength maintenance properties of repaired IACs.

Y-TZP are yet to be elucidated. Zirconia-veneered fractures represent an inconvenience to the patient; concerns may include extra replacement costs and additional chair time. Therefore, the integrity of zirconia-veneered prostheses should be continuously monitored.

High vs Low Modulus of Elasticity for Prostheses

Modulus of elasticity (E) is represented by the stiffness of a material within the elastic range and can be determined from a stress-strain curve (Table 3-4). In the case of prostheses, a higher elastic modulus is present in materials in the glass-matrix or polycrystalline ceramic categories as well as metal ceramics; materials of a lower modulus include the resin-matrix ceramics and fiber-reinforced composite families. During the early days of modern dental implantology, Brånemark and colleagues recommended that artificial teeth be made of acrylic resin, as it was empirically thought to compensate for the resilience of the periodontal ligament.[83] Because of the success of dental implant therapy, as well as partial and single-unit restorations, ceramicbased restorations began to be used more frequently.

The successful history of the ceramic-layered prosthesis for restorative dentistry notwithstanding, ceramic does not necessarily represent end-stage material in the context of its elastic modulus. Improvements in stress shielding, or mechanically mediating bone response, have long been desired and expected with materials such as resin-matrix ceramics and fiber-reinforced composites, which do not pose such a high elastic contrast between bone and prosthetic systems.[84]

Fatigue performance data of molar crowns fabricated with a variety of materials, including IACs, metal ceramics, CAD/CAM resin-matrix ceramics, and layered or repaired CAD/CAM crowns, reveal that regardless of material chosen for a molar crown on a locking-taper IAI, the characteristic strength during fatigue is not statistically different from metal ceramics—typically known as the gold standard (Fig 3-3).[85] Because previous evaluation of the locking-taper IAI design has shown that resin-matrix ceramics (CAD/CAM or hand-layered by a technician) do not generally need abutment or framework support, as is traditionally recommended for porcelain-layered resin-matrix ceramics or polycrystalline materials, comparisons for that class of materials were made with prefabricated abutments (Fig 3-4).[47,86–91]

Fig 3-4 Polarized light micrograph of a buccolingual section of an IAC. Because the titanium surface (which will be bonded) is sandblasted with aluminum oxide followed by metal priming, chemical and mechanical adhesion is improved, and final support of the layered resin-matrix ceramic-based material is not critical, as it is for porcelain layered glass-matrix or polycrystalline ceramic copings. Note that a unique feature of the pure interference fit implant abutment design—the absence of a screw—results in a full contour solid Ti-6Al-4V abutment, which provides increased strength.

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Conclusion

Prosthetic restoration of implants should be acknowledged as a system in which the choices of implant hardware and bulk material, the implant-abutment connection design, the restoration’s material and type, and patient-related and fabrication conditions are considered of utmost importance in defining future complication rates, chair time, and costs of maintenance.

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28. Schmitt CM, Nogueira-Filho G, Tenenbaum HC, et al. Performance of conical abutment (Morse taper) connection implants: A systematic review. J Biomed Mater Res A 2014;102:552–574.

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31. Chapman RJ, Grippo W. The locking taper attachment for implant abutments: Use and reliability. Implant Dent 1996;5:257–261.

32. Machado LS, Bonfante EA, Anchieta RB, Yamaguchi S, Coelho PG. Implant-abutment connection designs for anterior crowns: Reliability and failure modes. Implant Dent 2013;22:540–545.

33. Freitas-Júnior AC, Bonfante EA, Silva NRFA, Marotta L, Coelho PG. Effect of implant-abutment connection design on reliability of crowns: Regular vs. horizontal mismatched platform. Clin Oral Implants Res 2012;23: 1123–1126.

34. Almeida EO, Freitas-Júnior AC, Bonfante EA, Rocha EP, Silva NRFA, Coelho PG. Effect of microthread presence and restoration design (screw versus cemented) in dental implant reliability and failure modes. Clin Oral Implants Res 2013;24:191–196.

35. Almeida EO, Freitas-Júnior AC, Bonfante EA, Silva NRFA, Coelho PG. Reliability evaluation of alumina-blasted/acid-etched versus laser-sintered dental implants. Lasers Med Sci 2013;28:851–858.

36. Martins LM, Bonfante EA, Zavanelli RA, et al. Fatigue reliability of 3 single-unit implant-abutment designs. Implant Dent 2012;21:67–71.

37. Freitas-Júnior AC, Bonfante EA, Martins LM, Silva NRFA, Marotta L, Coelho PG. Effect of implant diameter on reliability and failure modes of molar crowns. Int J Prosthodont 2011;24:557–561.

38. Suzuki M, Bonfante E, Silva NRFA, Coelho PG. Reliability testing of indirect composites as single implant restorations. J Prosthodont 2011;20:528–534.

39. Bonfante EA, Suzuki M, Lubelski W, et al. Abutment design for implant-supported indirect composite molar crowns: Reliability and fractography. J Prosthodont 2012;21:596–603.

40. Bonfante EA, Suzuki M, Witek L, et al. Reliability of resin nano ceramic and metal ceramic implant-supported crowns. [Proceedings of the IADR General Session 2012].

41. Bakke M, Michler L, Han K, Möller E. Clinical significance of isometric bite force versus electrical activity in temporal and masseter muscles. Scand J Dent Res 1989;97:539–551.

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47. Bozkaya D, Müftü S. Mechanics of the tapered interference fit in dental implants. J Biomech 2003;36:1649–1658.

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50. Freitas AC, Bonfante EA, Rocha EP, Silva NRFA, Marotta L, Coelho PG. Effect of implant connection and restoration design (screwed vs cemented) in reliability and failure modes of anterior crowns. Eur J Oral Sci 2011;119:323–330.

51. Nissan J, Narobai D, Gross O, Ghelfan O, Chaushu G. Long-term outcome of cemented versus screw-retained implant-supported partial restorations. Int J Oral Maxillofac Implants 2011;26:1102–1107.

52. Sailer I, Mühlemann S, Zwahlen M, Hämmerle CHF, Schneider D. Cemented and screw-retained implant reconstructions: A systematic review of the survival and complication rates. Clin Oral Implants Res 2012;23(suppl 6):163–201.

53. Hirata R, Bonfante E, Machado L, Tovar N, Coelho P. Mechanical evaluation of four narrow-diameter implant systems. Int J Prosthodont 2014;27: 359–362.

54. Freitas-Júnior AC, Bonfante EA, Martins LM, Silva NRFA, Marotta L, Coelho PG. Reliability and failure modes of anterior single-unit implant-supported restorations. Clin Oral Implants Res 2012;23:1005–1011.

55. Freitas-Júnior AC, Almeida EO, Bonfante EA, Silva NRFA, Coelho PG. Reliability and failure modes of internal conical dental implant connections. Clin Oral Implants Res 2013;24:197–202.

56. Freitas-Júnior AC, Rocha EP, Bonfante EA, et al. Biomechanical evaluation of internal and external hexagon platform switched implant-abutment connections: An in vitro laboratory and three-dimensional finite element analysis. Dent Mater 2012;28:e218–e228.

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04

Biologic Response to Dental Implants

Jeffrey Lehrberg | Paulo G. Coelho

The introduction of exogenous materials into tissues results in multiple complex spatiotemporal events occurring at the molecular and cellular levels. Dental implants are a treatment modality that exemplifies the successful application of exogenous materials to the human body. Characteristics of both the implant and the surgical procedure can have a profound effect on the biologic response elicited by the surrounding tissues. Substrate, surface topography, geometric design, osteotomy dimensions, patient health, and surrounding bone quality are only a few of the parameters that act both individually and in concert to influence the organism’s biologic response and subsequent outcome of the procedure.[1]

Dental implants have met with great success over the years as a result of their ability to integrate with the surrounding bone, a phenomenon called osseointegration .[2] Although this term was originally used to describe bone-to-implant contact at the light microscope level, osseointegration now encompasses all of the events that occur during postinsertion peri-implant wound healing and subsequent bone regeneration.[3] While osseointegration can occur with a number of materials, it is most often used to describe the reaction of bone tissues to titanium or titanium coated with calcium phosphate derivatives.[4]

Titanium is frequently used as an implant material because of its mechanical properties and (perhaps most importantly) because of the biologic response that it evokes. Titanium has been described as being a biocompatible or bioinert material, which implies that the tissues surrounding a titanium implant respond in a manner analogous to bone-fracture healing.[4–6] Although bone-fracture healing and osseointegration are similar in many regards, they are not equivalent.[6] For example, unlike fracture healing, osseointegration does not include the differentiation of mesenchymal progenitor cells into chondrocytes, even though the expression of many chondrogenic genes has been reported.[6,7] Despite the gaps present in our current understanding of osseointegration, many important pathways and cellular events have been deduced. This chapter reviews some of the important cellular and molecular mechanisms that are involved in peri-implant wound healing and bone regeneration. Fig 4-1 Biologic response following initial injury. This illustration depicts the early cellular events following the creation of an osteotomy and placement of an implant (1). Creating the osteotomy introduces blood cells (shown in red) and serum proteins (shown in purple) into the void (2). The alveolar bone shows cortical bone and trabecular bone. The cortical bone is comprised of concentric osteons lined with osteocytes (3). In the center of one of the osteons, a Haversian canal possessing blood and lymphatic vessels and a nerve are shown (4). Apical to the cortical bone is the spongy trabecular bone (5).

Early Events in Peri-implant Wound Healing

Regardless of implant manufacturer or style, the first event that occurs during an implant procedure is the initial injury to the tissue in the edentulous region that is required to produce an osteotomy (ie, the void or crypt where the implant will reside). The laceration of blood vessels in the highly vascularized gingival tissues introduces blood and serum factors into the osteotomy space and activates multiple injury-response pathways, including the innate immune system, the kinin-generating system, and the complement system (Fig 4-1). In addition, the initial injury results in the recruitment of platelets to the wound site.[8]

Protein adsorption

As the implant is placed in the osteotomy, serum proteins that are present in the osteotomy adsorb onto the implant surface, creating a dynamic provisional matrix or biofilm[8] (Fig 4-2). Depending on the coating (eg, titanium, hydroxyapatite), the surface of the implant itself can undergo electrochemical changes in response to the proteins that have begun to adsorb on it and the osteotomy microenvironment.[9] Some of the proteins that comprise the biofilm include vitronectin, glycosaminoglycans, bone sialoprotein (BSP), albumin, osteopontin (OPN), fibrinogen, fibronectin, and immunoglobulin G (IgG), among others.[9–11] The initial proteins on the implant surface exist in a dynamic state and are eventually replaced by alternate proteins as wound

Fig 4-2 Protein adsorption. This illustration depicts serum proteins adsorbing on the implant surface. The proteins found in blood and serum, which had filled the osteotomy at the moment of injury (see Fig 4-1), now adhere to the implant surface, creating a coating known as a biofilm (shown in purple and indicated by the black arrow ).

healing progresses.[12] The quantitative and qualitative aspects of the proteins initially adsorbed onto the implant surface are crucial and will later go on to influence the subsequent peri-implant wound-healing response.[13]

The surface properties of a given implant can provoke conformational changes in the proteins that adhere to it. The conformational changes induced by the implant surface can expose certain protein- and cell-specific amino acid sequences in the proteins, adding another level of complexity to wound-healing fate.[11] An example of implant surface characteristics affecting adhered proteins can be seen in the adsorption and subsequent conformational change of fibrinogen on the implant surface, which results in the recruitment of phagocytes and other cells.[14,15] Additionally, the conformational change of fibrinogen in response to implant surface characteristics exposes an epitope that makes it conducive to cleavage by thrombin; this in turn permits subsequent coagulation and clotting events during the peri-implant healing process.[16]

Another important protein that is adsorbed onto the implant surface and contributes to implant peri-implant wound healing is fibronectin. Extracellular fibronectin on the implant surface influences cell functions and fates via transmembrane integrin receptors on cells in the vicinity of the implant.[17] Like fibrinogen, fibronectin adsorbed on the implant undergoes conformational changes that have wide-ranging effects.[17,18] For example, after adsorption, fibronectin exposes an ArgGly-Asp (RGD) epitope domain that, during later stages of bone regeneration, will bind to osteoblasts, expressing cell surface molecules amenable to this signal.[9] In addition to cell adhesion, fibronectin/integrin interactions have been shown to be involved in osteoblast differentiation, survival, and pro- Fig 4-3 Platelet activation and inflammatory response. This illustration depicts the early immune responses mounted by the organism in response to an implant. After encountering the implant, resting platelets (shown in green) become activated and release signaling molecules and growth factors. Activated platelets release chemokines that attract immune cells (indicated by the black arrow ) to the implant microenvironment and play a role in angiogenesis.

Fig 4-4 Aggregation of activated platelets on the implant surface (indicated by black arrows ). The activated platelets release signaling molecules and growth factors involved in angiogenesis and stem cell recruitment, including histamine, serotonin, PDGF, FGF2, TGF-, IGF, and VEGF.

Fig 4-5 Thrombogenesis and angiogenesis. This illustration depicts the thrombin-mediated conversion and polymerization of fibrinogen to fibrin and the sprouting of new blood vessels in the osteotomy. The converted fibrin (1) is a major component of the blood clot. New blood vessels (2) are induced to grow via chemokines secreted by activated platelets and molecular signals such as VEGF. Angiogenesis is a critical event that occurs during peri-implant wound healing and serves to bring cells, signaling molecules, and growth factors to the implant site.

gression through the cell cycle as well as the deposition of bone minerals.[18–20] Like in the previous example of fibrinogen, implant surface characteristics can also affect fibronectin messenger RNA levels and the half-life of extracellular fibronectin, influencing downstream cellular and molecular events.[21]

Platelet activation and inflammatory response

Concurrent with the immediate adsorption of proteins onto the implant surface, the first cells to come into contact with the implant surface are erythrocytes and platelets[22] (Fig 4-3). Upon coming into contact with the surface of the implant and the recently adsorbed proteins, the platelets become activated and release signaling molecules and growth factors. Fibrinogen on the implant surface induces the platelets and mast cells to release the vasomodulatory neurotransmitters histamine and serotonin, along with platelet-derived growth factor (PDGF) and inflammatory chemokines. The release of these molecules results in further phagocyte accumulation and the recruitment of multipotent mesenchymal cells and osteoprogenitor cells.[14,23] In addition to the secretion of PDGF, neurotransmitters, and chemokines, platelets release a number of other proteins, some of which include those involved in osteoblast cell activation and migration (eg, fibroblast growth factor 2 [FGF2], transforming growth factor- [TGF-], insulin growth factor [IGF], and vascular endothelial growth factor [VEGF]).[11,23]

The platelets activated in response to implant surface properties soon begin to aggregate on the implant surface (Fig 4-4). Within a few hours, blood clotting around the implant starts to occur via the thrombin-mediated conversion and polymerization of fibrinogen to fibrin[15,24] (Fig 4-5). The activated platelets and blood clot play a very important role in the peri-implant wound-healing process. The blood clot/ platelet structure serves as a molecular signaling center and scaffold that allows for the recruitment and activation of the cells that are responsible for inflammation, angiogenesis, and subsequent bone regeneration[25] (see Figs 4-5 to 4-12).

Simultaneous to the activation of platelets and clot formation, acute inflammatory responses begin to take place.[8] Platelet-derived chemokines from the C, CC, CXC, and CX3C families attract the next cells that will come into contact with the implant: neutrophils and monocytes, respectively[8,11] (see Fig 4-3).

Although neutrophils are initially the most prevalent immune cells present, they are replaced by the monocytes (which at this point have differentiated into macrophages) after about 2 days.[8,11] In addition to immune cell recruitment, the chemokines released by platelets assist in the process of angiogenesis, a process that is essential for both the recruitment and maintenance of metabolically active osteoblast progenitors[8,11] (see Fig 4-5). Furthermore, signaling molecules released from the platelet and clot, including the cytokines granulocyte colony stimulating factor (G-CSF), granulocyte-macrophage colony stimulating factor (GM-CSF), tumor necrosis factor-α (TNF-α), interleukin (IL)-8, IL-6, and IL-1, form a positive feedback loop with macrophages, causing them to release even more cytokines.[8,11]

Cytokines released by macrophages such as those in the TNF-α family and the TGF- family will later be involved in the recruitment of mesenchymal stem cells to the implant site and, depending on whether permissive levels have been reached, the differentiation and activation of osteoclasts[26,27]

roa 04 Biologic Response to Dental Implants Fig 4-6 Stem cell recruitment and osteoblast activation. This illustration depicts the recruitment of multipotent mesenchymal stem cells (MSCs) to the osteotomy. MSCs (shown in blue) are recruited to the peri-implant microenvironment by signals released by platelets during early stages of the wound-healing process (1). The newly established blood vessels help bring MSCs and other cells to the peri-implant microenvironment (2). These recruited stem cells are then induced to differentiate into osteoblasts through multiple signaling pathways, including the bone morphogenetic protein (BMP) signaling pathway. Fig 4-7 Intracellular response of an osteoprogenitor cell to BMP2. This illustration shows a simplified BMP2 pathway diagram. Extracellular BMP2 (1) binds to type I and type II BMP receptors (2). The binding of BMP2 to the receptor complex allows Smad1/5/8 (3) to be phosphorylated (4). Smad4 (5) forms a complex with phosphorylated Smad1/5/8 proteins (6) and facilitates their translocation into the nucleus (7). Once inside the nucleus, Smad1/5/8 binds to DNA with the assistance of DNA-binding cofactors (8) and drives the transcription (9) of osteogenic master regulators Runx2 (10) and Osterix (Osx) (11).

(see Figs 4-6 and 4-8). During later stages of peri-implant healing, a higher ratio of proinflammatory cytokines (ie, TNF-α and IL-1) to bone-regeneration markers is correlated with decreased biomechanical strength and bone formation, reflecting the broad function of these molecules and their need for spatiotemporal regulation.[28]

In addition to the classical role they play in immunity, macrophages also participate in regeneration.[29,30] Macrophages have been shown to exhibit two phenotypic subsets: the M1 macrophage phenotype, which defends the host from invading viruses, bacteria, and parasites; and the M2 macrophage phenotype, which regulates wound healing and inflammation.[30,31] During healing around implants, macrophages might be involved in the regulation of the inflammation response (ie, during normal peri-implant wound healing) or, after being reverted to a more M1 phenotype, might fuse together and create foreign body giant cells that will go on to take part in a more pronounced foreign body reaction (eg, the reaction seen in implant failure).[8,31,32]

Vascularization of the peri-implant microenvironment

The next event to occur during peri-implant wound healing is angiogenesis, the vascularization of the peri-implant microenvironment (see Fig 4-5). Angiogenesis is the process through which new blood vessels develop from preexisting ones. In the context of the peri-implant wound healing, angiogenesis is a critical process that will allow for the transport of cells involved in bone regeneration and their subsequent nourishment (Fig 4-6).

An important molecule involved in angiogenesis that is expressed during peri-implant wound healing is VEGF.[33] VEGF has been known to bind and become sequestered by glycosaminoglycans, fibrinogen, and fibronectin—all proteins that have been found both on the implant surface and in the blood clot.[34] VEGF concentration can be altered by the alternate sequestration and release of the protein via proteases such as matrix metalloproteinases (MMPs).[34] Through the degradation of the extracellular matrix (ECM) molecules that constitute the clot and surrounding tissues, VEGF is released and allowed to exert its effect on angiogenesis.[34] Through the action of VEGF receptors (VEGFRs) on the surface of endothelial cells, new blood vessels form; these in turn serve to bring cells, signaling molecules, and growth factors to the implant site (see Fig 4-5).

Angiogenesis and bone regeneration are physiologic actions that are closely linked.[35] In addition to playing a role in vascularization of the peri-implant microenvironment, VEGF is highly expressed in osteoblast progenitors and helps drive osteoprogenitors into an osteoblastic state[35,36] (see Fig 4-6). Fig 4-8 Osteocyte apoptosis in response to microdamage. This illustration depicts apoptosis of an osteocyte (1) following microdamage to the preexisting bone. Microdamage (indicated by black arrows ) causes nearby osteocytes to undergo apoptosis. Surrounding osteocytes (2) respond by releasing TNF-α, macrophage colony stimulating factor, and receptor activator of NF-κB ligand (RANKL), important regulators of osteoclastic activity.

Fig 4-10 Bone deposition in the implant microenvironment. Osteoblasts taking part in contact osteogenesis deposit a noncollagenous matrix (rich in calcium, phosphorous, chondroitin sulfate, BSP, OPN, and proteoglycans) onto the implant surface (1). This matrix is deposited by osteoblasts taking part in contact osteogenesis (2). Osteoblasts also generate bone on the preexisting bone of the osteotomy wall (distance osteogenesis) (3). During bone regeneration, some osteoblasts become trapped within the accumulating matrix, where they terminally differentiate into cells called osteocytes (4).

Fig 4-9 Osteogenesis in the implant microenvironment. Osteoblasts on the implant surface (1) generate de novo bone in a process called contact osteogenesis . The localized grouping of multinuclear cells called osteoclasts (2) and osteoblasts is known as a basic multicellular unit (BMU) (3). New bone can also be created on the osteotomy wall in a process called distance osteogenesis (4). The amount of osteoclastic activity that occurs is largely regulated by osteocytes (5) surrounding regions of bone damage.

Stem cell recruitment and osteoblast activation

After the establishment of new blood vessels in the periimplant microenvironment, multipotent mesenchymal cells (MSCs), pericytes, and fibroblasts derived from the periosteum and surrounding tissues are recruited to the implant site[3,11,25,37,38] (see Fig 4-6). Molecules released by platelets during the platelet activation stage (eg, PDGF, TGF-, and BMPs) aid in the recruitment of these mesenchymal cells to the peri-implant microenvironment.[39] The differentiation of the recently recruited MSCs involves the coordinated effort of multiple signaling pathways, including the FGF, wingless (Wnt), notch, hedgehog, and BMP signaling pathways.[40] Of these pathways, the BMPs have received considerable attention owing to their powerful osteoinductive abilities.[40]

BMPs are a group of highly conserved cytokines that are members of the TGF- superfamily and are involved in multiple developmental and regenerative processes.[39,41] BMPs are perhaps most well known for their ability to drive multipotent progenitor cells into an osteoblastic fate.[39,41] While many BMPs are expressed during bone regeneration, BMP2 is necessary and required for the initiation of the process.[26,42]

During fracture healing, BMP2 is expressed in endothelial cells and vascular smooth muscle cells prior to the onset of its expression in osteogenic cells.[43] Briefly, BMP2 induces osteogenesis by binding to type I and type II BMP receptors (Fig 4-7). Binding of BMP2 to the receptors triggers the intracellular phosphorylation of Smad proteins (eg, Smad 1/5/8). Phosphorylation of Smad1/5/8 transcription factors allows them to be translocated into the nucleus (via Smad4), where they then drive the expression of osteogenic master regulators such as Runx2 and Osx.[40] Runx2 and Osx expression influences future differentiation decisions of multipotent MSCs.[40,44]

Expression of Runx2 in MSCs will result in their differentiation into preosteoblasts.[40,44] The subsequent coexpression of both Runx2 and Osx results in the differentiation of preosteoblasts into immature osteoblasts.[40,44] In addition to regulating differentiation, Osx expression also affects the expression of osteocalcin (OCN), BSP, type 1 collagen, and alkaline phosphatase (ALP), molecules that perform multiple functions, including adhesion, differentiation, and bone mineralization.[40,44,45]

Bone Regeneration and Implant Macrogeometry

This is the point in the peri-implant wound-healing process where implant macrogeometry (along with osteotomy dimensions) begins to have a more profound effect on the ensuing regenerative process.[46] Peri-implant bone regeneration and its consequent timing and quality are a direct reflection of the biomechanics at the implant-osteotomy interface. Although the most conservative hypothesis suggests that bone is regenerated around all implants in the same manner (ie, through the same cellular and molecular mechanisms, irrespective of design), the interplay between implant macrogeometry and osteotomy dimensions during the early stages of the regenerative process can result in distinct types of bone forming around the implant.[46,47]

Osteoblast extracellular matrix deposition

Bone regeneration takes place when osteoblasts synthesize a noncollagenous matrix rich in calcium, phosphorous, chondroitin sulfate, BSP, OPN, and proteoglycans onto the implant surface[45,48] (Figs 4-8 to 4-10). This matrix represents a distinct morphologic entity that is analogous to the cement lines found in circumferential rings of osteons (ie, the obvious demarcation point between new and old bone).[11,45,49]

OPN contains a sulfated RGD domain and a calciumbinding domain that have been associated with osteoblast attachment and calcium phosphate crystal growth, respectively.[45] BSP also has a calcium-binding domain, and it has been suggested that BSP may be the source of calcium phosphate crystal nucleation.[45] As inorganic crystals continue to grow on the cement line, they provide an anchorage point for type 1 collagen fibers.[45] The collagen fibers begin to assemble on the cement line and subsequently mineralize.[45] ALP, a marker of osteoblast differentiation, is also involved in the initiation of mineralization.[39]

As the osteoblasts continue to regenerate bone, some become trapped within the accumulating matrix, where they terminally differentiate into cells called osteocytes (see Fig 4-10). The osteocytes reside in hollow chambers (called lacunae ) within the growing bone and communicate and exchange nutrients through gap junctions on long cytoplasmic processes called canaliculi (Figs 4-11 and 4-12). Osteocytes are responsible for signal transmission and bone homeostasis. At this point, the nascent bone (with its characteristic random fiber orientation and flexibility) is referred to as immature bone or woven bone . Over time, the woven bone is remodeled, resulting in stronger bone with organized fibers.

Contact and distance osteogenesis

Growing bone can accrue on two surfaces in the peri-implant microenvironment: on the surface of the implant itself or on the preexisting bone that makes up the walls of the osteotomy (see Fig 4-9). These two locations of bone growth reflect two different bone-growth processes called contact osteogenesis and distance osteogenesis .[50] During contact osteogenesis, osteoblasts on the implant surface create de novo bone in the manner described above.[25] In distance osteogenesis, new bone is similarly deposited, albeit directly on the surface of the preexisting bone of the osteotomy wall.[50] Of the two bone-growth processes, contact osteogenesis is the most critical because mechanical stabilization of the implant will not occur without it.[25]

Osteoclastogenesis

Concomitant with osteoblast bone deposition is a process called osteoclastogenesis . Osteoclastogenesis describes the commitment, differentiation, multinucleation, and maturation of specialized cells of hematopoietic origin called

osteoclasts[51] (see Figs 4-8 and 4-9). Osteoclasts are the cells responsible for bone resorption during both normal homeostatic processes and after injury.

Osteoclastogenesis and osteoblast bone deposition are highly linked processes. After bone damage, osteocytes in the immediate vicinity of the injury site undergo apoptosis[52,53] (see Fig 4-8). In response to signals released by apoptotic osteocytes, neighboring osteocytes that have survived the initial injury secrete TNF-α, macrophage colony stimulating factor, and RANKL.[26,27,52] RANKL can induce the differentiation of preosteoclastic cells into osteoclasts by binding to the transmembrane receptor RANK.[27] Osteoprotegerin (OPG) is an extracellular decoy receptor that binds to RANKL, preventing the differentiation and activation of osteoclasts.[27] The regulation of RANKL/OPG ratio, as controlled by numerous cytokines, dictates osteoclastogenic events.[27]

Osteocytes that are induced to undergo apoptosis following microdamage become focal points for osteoclast resorption.[52,53] Localized groups of osteoclasts and osteoblasts, which are responsible for the resorption and subsequent redeposition of bone at damaged sites, are known as a basic multicellular unit (BMU).[54]

Osteoblast bone deposition and osteoclast-mediated bone resorption by BMUs is a dynamic process that occurs throughout the life of the organism.[51] Following implantation, newly regenerated bone is continuously remodeled, resulting in the increased organization of lamellar structures[55] (see Figs 4-11 and 4-12). It has been shown that the magnitude of osteoclastic activity is intimately tied into implant macrogeometry. For example, screw-root form (SRF) implants under load exhibit significantly higher levels of RANKL when compared with unloaded implants.[56] Although osteoclast activity likely occurs in all implants in response to the damage inflicted by drilling, implant designs that attempt to minimize this activity (either through the use of slow-speed drilling or plateau-root form [PRF] implants) can achieve temporally accelerated secondary stability compared with implants that do not.[57–59]

Influence of Implant Macrogeometry on Bone-Regeneration Outcomes

The interplay between osteotomy dimensions and implant macrogeometry can result in the formation of distinct types of peri-implant bone[46,47] (see Figs 4-11 and 4-12). Just as in the case of implant surface chemistry, the conditions created at the bone-implant interface as a result of implant macrogeometry can have a profound influence on all of the cellular and molecular processes that have been discussed in this chapter. For example, inadequate space between the osteotomy wall and the implant can interfere with protein adsorption, clot formation, the infiltration of immune cells and blood vessels, and the migration of osteogenic cells.[24,45,57,60–63] Additionally, if the diameter of the implant and osteotomy are incongruous, friction at Fig 4-11 Interfacial bone remodeling. This illustration depicts the type of bone that regenerates around implants in close contact with the osteotomy wall (eg, SRF implants). Peri-implant bone has a cortical morphology with compact lamellae (1). New osteocytes communicate through long cytoplasmic processes called canaliculi (2). Trabecular-like bone (3) is not typically seen around implants in close contact with the osteotomy wall. Fig 4-13 Micrograph of a representative SRF implant demonstrating bone resorption (Toluidine blue stain). This implant was placed in direct contact with surrounding bone (placed in a rabbit tibia), with the perimeter of the implant indicated by the red line . The yellow line indicates the boundary from the implant surface where cell-mediated interfacial remodeling occurred as a result of microfractures or pressure necrosis (ie, the space between the red and yellow lines was once filled with bone). Microfractures are indicated by the green arrows . (Reprinted with permission from Coelho et al.[46] )

Fig 4-12 Intramembranous-like bone remodeling. This illustration depicts the type of bone that regenerates around implants that have a gap between the implant and the osteotomy wall (eg, PRF implants). The bone that is found adjacent to PRF implants has organized lamellae (1) and large Haversian-like structures (2). Initially, the bone that forms around PRF implants is trabecular in nature (3). This trabecular-like bone is later replaced by the more organized structures seen in (1) and (2). New osteocytes (4) communicate through canaliculi and are responsible for maintaining bone homeostasis.

the interface can result in compression necrosis and increased osteoclastogenic activity[24,57,60–63] (see Figs 4-8, 4-9, and 4-11).

Briefly, the bone that regenerates around implants that are in close contact with the osteotomy wall (eg, SRF implants or implants under high insertion torque) exhibits a morphology reflective of the adjacent bone. For example, if placed in cortical regions, the resulting bone will have a cortical morphology comprised of osteons with compact lamellae.[24,47,58,61,64] If, on the other hand, the implant design allows large gaps to form between the implant body and the osteotomy, then bone with morphologic characteristics distinct from what is observed around SRF implants will regenerate[24,47,55,58,61] (see Fig 4-12).

PRF implants possess large gaps between the fins or plateaus; these gaps are called healing chambers .[47] Within the healing chambers, bone initially exhibits a trabecular morphology[24,58] (see Figs 4-10 and 4-12). The early trabecular-like bone that forms in healing chambers is later replaced by bone possessing large Haversian-like structures surrounded by organized lamellae.[24,47,55,61] The distinct types of bone healing that occur around SRF and PRF implants are discussed in greater detail below.

Interfacial remodeling healing of SRF implants

The type of healing that typically occurs around SRF implants is known as interfacial remodeling .[61,65] When an SRF implant is placed or “screwed” into an osteotomy, the surrounding bone comes into direct contact with the implant; it is this direct contact that provides the initial stability of SRF implants prior to biologic activity.[58,61,65] The amount of force exerted via the action of screwing an SRF implant into bone is a function of the diameter of the osteotomy and the implant and how the implant’s geometry distributes strain to the adjacent bone tissue. Accordingly, the level of insertion torque required to place SRF implants is inversely proportional to the level of micromotion that will occur immediately after placement. Although a high insertion torque leads to an initial level of stability, long-term stability has the potential to be adversely affected: Excessive strain results in microfractures and possibly even pressure-induced necrosis of the surrounding bone.[57,60,63,66]

Once an SRF implant has been inserted—and subsequent to the initial biologic response discussed in the beginning of this chapter—a period of interfacial, cell-mediated bone resorption takes place.[47,67] The resorption and remodeling that take place are caused by the yield strength of bone being exceeded, resulting in microfractures or pressure bone necrosis. This ultimately leads to bone resorption extending several hundred micrometers away from the implant surface[68–71] (Fig 4-13).

The extensive bone resorption that occurs following the insertion of an SRF implant nullifies the primary stability achieved via high insertion torque—a quality highly desired by some clinicians (a high primary stability can support single-stage, “teeth-in-a-day” restorations). This reduction in stability is regarded as the implant stability dip .[72] The remodeling region, characterized by large voids or spaces partially filled with new bone, is illustrated in Fig 4-13 and provides a possible mechanism for why the implant stability dip occurs: The implant is no longer in direct contact with the osteotomy wall. Fig 4-14 Intramembranous-like healing during osseointegration (Stevenel blue and van Gieson acid fuchsin stain). A sequence showing the morphology of bone after healing times of 1 week (a) , 3 weeks (b) , 6 weeks (c) and 12 weeks (d) after implantation of Bicon implants in dogs. (a) After 1 week, growth factors present in the blood clot that filled the healing chambers develop a connective tissue network and pathway for cell migration. (b) Three weeks after implantation, the first evidence of woven bone begins to be observed. (c) At 6 weeks, the deviation from interfacial remodeling is apparent: Woven bone begins to form throughout the entire chamber, and the first appearance of osteons begins to emerge (osteons indicated by blue arrows ). (d) At 12 weeks after implantation, woven bone has begun to give way to the initial formation of lamellar bone (osteons indicated by yellow arrows ). (Reprinted with permission from Coelho et al.[46] )

After the period of resorption, appositional growth occurs from the osteotomy wall back toward the implant surface. The void that resulted from the resorption of bone is filled with newly formed woven bone; this bone eventually establishes contact with the implant surface and provides secondary stability.[24,58,61,65]

Intramembranous-like healing of PRF implants

Unlike the intimate primary fit that occurs between bone and the surface of most SRF implants, PRF implants (and SRF implants that have sufficient gaps between the pitch of the screws and the minor diameter of the implant body) possess healing chambers between their plateaus or fins.[24] Upon insertion, these healing chambers fill with, and provide space for, the various growth, angiogenic, and regenerative factors discussed previously in this chapter.[61] Although the absence of intimate contact precludes the primary stability seen in SRF implants, the large healing chambers are key contributors to secondary stability: The high quantity of progenitor cells, growth factors, and overall degree of vascularization found within the chambers aids in the rapid ossification and eventual osseointegration of the implant.[73]

The bone healing that takes place within the healing chambers of PRF implants has been described as intramembranous-like.[47] The healing chambers are initially filled with blood clots, as well as the factors necessary for regeneration described above. The blood clots and connective tissue gives way to the development of woven bone, which is later replaced by lamellar bone via remodeling.[24,47,58,61,74] Figure 4-14 depicts the sequence of intramembranous-like healing that takes place at 1, 3, 6, and 12 weeks.

Long-Term Influence of Implant Macrogeometry on Bone Morphology

This chapter has mainly focused on events occurring minutes to days after implant insertion, but what about the long-term biologic responses? In the absence of illness or injury, arguably the most significant long-term event that occurs after implant placement is bone remodeling, and as new research of processes such as platform switching has shown, implant characteristics such as macrogeometry and design have a significant influence on long-term responses.[75–78]

During the osseointegration of an SRF implant, the bone that will intimately grow along its perimeter eventually becomes a congruous extension of the adjacent bone. SRF implants placed in regions characterized by trabecular bone develop lamellar bone with medullary spaces; implants placed in regions characterized by cortical bone develop lamellar bone that eventually blends into a cortical bone Haversian system via remodeling.[79–82] Further functional loading on SRF implants induces bone remodeling Fig 4-15 SRF implant retrieved after 3 years in function (Stevenel blue and van Gieson acid fuchsin stain). This image shows the representative type of bone found around SRF implants: compact lamellar bone with small marrow spaces. (Reprinted with permission from Coelho et al.[46] ) Fig 4-16 Micrographs showing long-term bone morphology around Bicon implants retrieved from humans (toluidine blue stain). (a) At 1 year postloading, the bone present in the healing chamber is a mixture of lamellar bone (L) and woven bone (W). After 1 year of loading, the morphology of bone found within the healing chamber is remarkably consistent. At both 8 years (b) and 17 years (c) , the bone found in the healing chamber has a lamellar-like configuration.

that results in higher degrees of bone organization.[47] Bone remodeling is most evident toward the coronal end of an SRF implant, and in most cases, long-term bone has generally been described as mature, compact lamellar bone with a minute number of marrow spaces[64,83,84] (Fig 4-15).

Long-term properties and morphology of bone surrounding PRF implants

There have been a number of longitudinal studies analyzing the morphologic characteristics of bone surrounding PRF implants.[48,55,85,86] In all of the long-term studies—regardless of functional loading time or any other implant or clinical parameter—the bone that surrounds PRF implants is distinct from that which surrounds SRF implants.

From loading up until 1 year in function, a mixture of both woven and lamellar bone can be observed surrounding PRF implants, with an absence of connective tissue or evidence of epithelial migration[48,55,86] (Fig 4-16a). At 1-year postloading and beyond, the surrounding bone is remarkably similar and consistent. Bone examined surrounding implants in function from a period ranging from 1.5 to 24 years exhibited classic lamellar bone structures with Haversian-like canals and/or osteons with concentric lamellae[55,86] (Fig 4-16).

Contrary to what is observed around SRF implants, the Haversian-like structures around PRF implants run between the plateaus (ie, perpendicular to the long axis of the implant); these structures are found in both trabecular and cortical type bone—a morphologic characteristic that is unique to PRF implants.[86] In a series of human retrieval studies where implants were removed for prosthetic reasons, it was shown that bone displaying multiple osteons later progressed into a Haversian-like structure, further increasing its mechanical properties.[48,55,85,86]

Conclusion

Despite the long history of dental implant use, we are still only beginning to fully elucidate the molecular and cellular mechanisms responsible for peri-implant wound healing and bone regeneration. Implanting exogenous materials into a biologic compartment induces complex molecular and cellular events in the surrounding tissues. PRF implants, which are the focus of this book, utilize a PRF implant design whose unique macrogeometry results in a similarly unique Haversian-like pattern of bone regeneration. The topics discussed in this chapter should have provided a foundation for understanding the biologic response to not just PRF implants but dental implants in general: The molecular and cellular events of peri-implant wound healing and bone regeneration are orchestrated by many implant properties, including surface characteristics, surface chemistry, osteotomy dimensions, and implant macrogeometry.

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05

Engineering Aspects of Bicon Implants

Soroush Irandoust | Jeffrey Lehrberg | Vincent J. Morgan | Sinan Müftü

A dental implant system consists of an implant and an abutment, whose purpose is to provide an anchor for the prosthetic reconstruction of missing teeth. The implant is the component inserted and eventually embedded into the jaw bone, and the abutment is the component that supports and retains the prosthesis.[1] Where prostheses are concerned, a fixed prosthesis is attached to the abutment by cementation, an occlusal screw, or other bonding method, whereas a removable prosthesis refers to a denture or partial denture that is retained mechanically by the abutment.

The location where the implant and abutment connect is called the implant-abutment interface (IAI). Conventional implant systems typically secure the abutment to the implant through mechanical means, and one of the most important factors influencing the long-term success of a dental implant system is the reliability and the stability of this IAI.[2] The three most common IAI designs used in modern dental implants are screw-retained, screw-retained taper or taperintegrated screw (TIS), and Morse taper[3] (Fig 5-1).

In the dental implant literature, the terms conical abutment , Morse taper abutment , and locking-taper abutment are frequently used interchangeably; however, these terms are not always synonymous. Almost all dental implant systems that rely on a taper to secure the abutment and the implant use a Morse taper design. Briefly, a cone-shaped male end or shank of a given taper angle is inserted into a female receiver with an equal taper angle. The degree or size of the angle for both the male and female parts influences how that taper is defined and what its attributes are. The angle, defined as the semicone angle , is measured from the centerline to the slope of the taper, angle θ (see Fig 5-2).[4] Generally speaking, tapers with total angles greater than 14 degrees (or semicone angles greater than 7 degrees) are called self-releasing , steep , or fast . These types of tapers are used to aid in the alignment of certain machines or tools (eg, milling machines).[4] Self-releasing tapers need to be secured with additional methods such as the use of a drawbar and screws.

Literature Survey of TIF Connection Methods

Fig 5-1 A selection of four commercially available implants that utilize a screw to affix the abutment to the implant. Implant systems 1 and 2 use a TIS strategy to secure the abutment to the implant, implant system 3 utilizes a Morse taper (TIF) at the IAI, and implant system 4 uses the traditional screw-retained IAI design.

Alternatively, tapers with total angles less than 14 degrees (or semicone angles less than 7 degrees, and typically below 2 degrees) are called self-holding , self-locking , or simply locking tapers . As their name implies, these types of tapers do not need to be secured with additional means and hold in place when axial force is applied.[4] Where dental implants are concerned, locking tapers have also been described as tapered abutments or possessing a taperedinterference fit (TIF)—a more precise term that is used for the remainder of this chapter. Bicon implants possess a semicone angle of 1.5 degrees, and thus their abutments are retained via a TIF at the IAI.

As previously stated, a tapered cylinder (ie, the abutment) is inserted into a matching tapered hole (ie, the implant well) via external force acting in the axial direction. This type of connection causes the diameter of the implant to slightly increase and the diameter of the abutment to slightly decrease. This interaction between the implant and abutment causes a normal stress to develop along the IAI; in fact, this contact pressure will increase with increasing axial force (an excellent situation for a prosthetic tooth in occlusion). However, if the geometry and the material properties of the interface are properly designed, there is no need for axial forces to keep it in place after the initial installation. (A detailed examination of the forces involved for a TIF is provided at the end of this chapter.) Compared with screw-retained interfaces, the lack of axial force needed for TIF implants presents a significant advantage, as the former requires preloading of the screw.

Over the last 20 years, many studies have been published highlighting the advantages and disadvantages of TIF connection methods. The next section of this chapter presents a survey of the literature relating to tapered abutments, including a catalog and discussion of general topics involved in the clinical use and engineering design of such IAI designs.

The authors conducted a survey of the literature, specifically searching for studies reporting on microbial/bacterial contamination in dental implant systems with conical/tapered abutments. The survey also included studies related to mechanical design of the conical/tapered abutment systems. The results of the literature survey showed that bone loss becomes a problem around the implant when either the IAI fails to deliver a proper level of microbial sealing or the interface is insufficiently stable. Furthermore, the following clinical factors are suggested by different studies to be effective in preventing this type of bone loss: providing a bacteria-proof seal, preventing micromovements between the implant and the abutment, performing a minimally invasive stage-two surgery, using abutments smaller than the diameter of the implant body (eg, platform switching), and placing the IAI coronal or subcrestal with respect to the bone level and the distance of this interface to the surrounding bone.[5–11] The following is a brief review of the studies that describe the aforementioned effects. A more detailed examination of the Bicon IAI can be found in chapter 6.

Microbial leakage at the IAI

Microbial leakage at the IAI has been identified as the most likely origin for implant system contamination and is one of the significant factors affecting the long-term stability and survival of the implant.[12,13] Contamination of the external and/or internal surfaces of an implant system during its installation may lead to peri-implantitis or result in treatment failure. As is the case with orthopedic implants, infected dental implants are difficult to treat and frequently require removal.[14]

Microorganisms from the oral microenvironment (teeth, tongue, tonsils, or buccal mucosa) are common sources of bacterial colonization for new implants.[15–19] Incidences of bacterial contamination are more common for partially edentulous patients.[20] Pathogenic microorganisms that put dental implants at risk include a range of gram-negative anaerobes and spirochetes, which are also implicated in periodontal disease (see chapter 6). Once pathogenic bacteria have contaminated an implant, both peri-implant pockets and internal openings on the implant body serve as reservoirs for continued proliferation.[21]

In general, 100% prevention of microbial leakage for the duration of the treatment is perhaps not possible, nor even feasible with currently existing implant systems.[9,12,13,17,22–25] Screw-retained implant systems in particular can harbor significant quantities of deleterious microorganisms.[12] Coelho et al[22] showed in their evaluation of the sealing capability of different implant systems that despite a degree of control concerning torque levels, none of the screw-retained or TIS implant systems shown in Fig 5-1 could maintain a bacterial seal. In their in vitro analysis of bacterial leakage, Aloise et al[26] showed the incidence of bacterial leakage to be on the order of 20% for two types of Morse taper implant systems. Although the tapered interface on TIS implant systems acts as a seal against bacterial leakage and colonization, it cannot completely prevent leakage because of the gap caused by the misfit between the components; furthermore, the rate of microbial leakage diminishes as the degree of misfit decreases and the tightening torque of the screw increases.[12,27]

Microgaps and micropumps: A fast lane for bacterial transmission

The infiltration of bacteria into peri-implant spaces can be facilitated through the presence of microgaps at the IAI. In a clinical setting, microgaps have the potential to be expanded when bending forces apply pressure on the screw joint.[16,22] Local enlargement of the marginal gap and initiation of a pumping effect (ie, micropump) caused by micromovements can disperse harmful bacteria throughout the IAI.[16,28] Moreover, it has been hypothesized that the chemotactic stimuli originating from the microgap promotes sustained neutrophil accumulation as bacteria are recruited to the implant surface; the activation of inflammatory cells then promotes increased osteoclast activity.[8] Thus, microbial leakage may be the cause of the bone loss observed in the first year of function for some dental implant systems.[8,17,29]

Bacterial colonization of the implant surface

Surface modifications can play a significant role in reducing bacterial colonization on dental implants. Extensive work has been carried out to identify the biochemical mechanism of bacterial adhesion and to design surfaces to minimize it. While most of the work concerning bacterial adhesion has been related to peri-implant colonization, the lessons learned can and should be applied to intra-implant cavity colonization.

An implant’s surface roughness, surface free energy, and chemistry all have significant effects on initial adhesion and eventual retention of oral microorganisms.[30–34] Initial bacterial adhesion and colonization of oral surfaces begins at opportune nucleation sites, such as the bottom of surface irregularities (eg, grooves, pits, or abrasion defects), where bacteria can find shelter to establish a strong attachment.[35] Various surface-modification techniques have been introduced to reduce bacterial adhesion, such as modifications to the surface roughness, sterilization and various forms of cleaning, the application of different coatings, ion deposition, electrochemical modification, the tethering of antibacterial agents, and even the simple smoothing of an intraoral hard surface to reduce points of attachment.[35–45]

IAI design and bacterial contamination

For implant systems using screw-retained abutments, closure at the recommended torques may reduce the potential adverse effects of microleakage.[46] Furthermore, contamination may also be reduced by using a washer, a silicone ring, varnish containing chlorhexidine, or cement-retained abutments.[13,28,29,47–49] Alternatively, despite some evidence to the contrary, most studies concerning the use of Morse taper or self-locking connections report a reduction, delay, or prevention of bacterial contamination.[7,9,23,25,50–55] The resistance of Morse taper implants to bacterial infiltration is caused by the conical shape of the IAI: Microgaps are minimized because of the higher contact pressure that is generated at the conical interface when inserting the abutment. Nevertheless, achieving a perfect seal still depends on the surface roughness of all components where they meet at the IAI; if the mating surfaces of a conical interface are excessively rough (eg, greater than several micrometers), bacterial contamination can still occur.[56,57]

Load carrying and transfer characteristics enabled by tapered abutment design

It has been suggested that prosthetic complications and peri-implant bone loss are reduced in implant systems that use tapered abutments, owing to the mechanical stability of their interface.[7,8,54] Mangano et al[58,59] performed a clinical evaluation of implants using a Morse taper connection and concluded that this type of system results in the successful rehabilitation of partially and completely edentulous arches, as well as scenarios calling for single tooth replacement in anterior and posterior areas of both arches. Furthermore, a Morse taper connection has been shown to have a reduced incidence of abutment loosening, a good cumulative survival rate, and a very favorable overall implant/ crown success rate.[54] Other studies have also shown that crestal bone changes around two-piece, nonsubmerged titanium implants are significantly influenced by possible movements between implants and abutments.[56] Because of the nature of the conical interface, significantly more material is present at the implant crest. This abundance of material increases the resistance of the implant system to bending moments that stem from the lateral components of the mastication forces. Additionally, the compressive and frictional forces at the conical interface make it more stable, with a reduction of loosening. The combination of the two effects likely renders micromotion at the bone-implant interface to a level that is below thresholds that would trigger resorption.

Influence of the IAI on peri-implant bone stress

Bone remodeling around a dental implant has a significant effect on the implant’s survivability. In addition to periodontal factors, the load transferred to the bone also plays a role in bone resorption and densification.[60] Chun et al[61] showed that when an implant system with a tapered IAI was used, a low level of stress was generated in the surrounding bone

(an indicator of success), loading conditions notwithstanding. Using the finite element method (FEM) combined with the Taguchi method, Lin et al[62] showed that an implant with a TIF connection performed better as a force-transmission mechanism than any other configuration. Later, using FEM to investigate bone loss and bone remodeling, Lin et al[63] concluded that the internal engagement type of the abutments (with or without TIF) did not influence the bone loss in the surrounding bone.

Chou et al[64] investigated the load transfer from widediameter short (WDS) and narrow-diameter long (NDL) Bicon implants to the surrounding bone. They demonstrated that relatively high strain around the tips of the implant plateaus indicated bone densification near the tips of the fins, and lower strain present in the areas between the fins indicated reduced bone density. Furthermore, a higher and more even distribution of strain in the peri-implant bone was generated by the WDS implant when compared with the NDL implant. Nevertheless, regardless of implant dimensions and simulated clinical scenarios, the development of high strain in the alveolar region was inevitable.[64] Chu et al[65] suggested that for an internal tapered abutment design, a narrower and deeper IAI was responsible for the biomechanical advantage observed by the reduction of stress concentration in the crestal region around an implant.

Design considerations of TIF systems

The long-term success of a dental implant system depends in part on the reliability and stability of the IAI mechanism.[2] Implant systems that utilize an external screw to retain the abutment have demonstrated that inadequate screw preload, mismatched mating components, and rotational characteristics of the screw can all cause screw loosening or fracture.[66] To counteract the risks associated with screwretained abutments, the implementation of appropriate screw material selection and the use of the recommended torque values during tightening have shown that when applied to earlier designs, a significant reduction in the incidence of loosening resulted.[1,67–70]

Wakabayashi et al[71] reviewed the nonlinear finite element techniques used in analyzing dental implant systems and concluded that the design of the next generation of implant systems would benefit from more realistic analyses. Following this aforementioned work, a design for interference fits via FEM was presented by Zhang et al.[72] Strozzi et al[73] derived a normalizing parameter for the stress concentrations around some type of press-fits, as a function of fillet radius, shaft radius, interference, and Young’s modulus. Gammoudi et al[74] investigated the pull-out response of cylindric posts.

The performance of various aspects of tapered IAI connection systems has been investigated experimentally by using FEM. Some aspects include the following: rotational loosening and removal torque of the abutment, axial displacements of tapered cone-screw (TIS) abutments as a function of tightening torque, pull-out force, stability under off-center occlusal loads, evaluation of different fixed partial prosthetics, reliability with respect to fatigue, and experimental evaluations of efficiency.[75–87] These analyses show that a significant correlation between the loosening and tightening torque values has been reported for TIS systems. Depending on the system, the torque efficiency (ratio of the loosening torque TL to tightening torque TT ) of the commercially available TIS systems varies from 0.85 to 1.1. Bozkaya and Müftü’s[88] analysis of one such TIS system revealed that the efficiency values that are greater than 1 happen when the connection starts to rely solely on the interference rather than on the combined action of the interference and screw. Furthermore, the strength of the tapered interface in a TIS abutment has been assessed experimentally and with FEM, and the tapered interface was found to be favorable in terms of resistance to bending forces and maximum tightening torque.[80,89] Finally, the stresses induced by off-axis loads were compared for tapered and butt-joint connections, and it was concluded that the tapered interface distributed stress more evenly compared with the butt-joint connection, and most importantly, the conical interface allowed a larger maximum tightening torque.[90]

Understanding the mechanics behind a given attachment method is critical when designing a dental implant system. The mechanics of the purely screw-retained abutments can be analyzed based on classic power screw formulas and with FEM.[91] The mechanics of the TIS systems have similarly been analyzed by simplified formulas and by using FEM.[88,92] The remainder of this chapter provides an overview of the attachment mechanics for TIF systems in light of new experimental findings.[3,93–95]

Mechanics of the TIF Connections

A more in-depth explanation of the mechanics behind a TIF is as follows: The self-locking nature of the tapered interface is ensured if the taper angle θ is less than the critical taper angle θ c . The critical taper angle can be shown to depend on the static friction coefficient µs of the matching components as follows: θefficient values are in the range of 0.3 to 0.6, which shows that cr = atan µs . Typically, dry-contact, metal-on-metal friction cotaper values are less than 16.7 degrees (corresponding to µs = 0.3) and thus should be considered self-locking.

Figure 5-2 provides a schematic description of a theoretic implant system with a generic TIF connection. An axisymmetric, cylindric coordinate system ( r,z ) is located at the top of the implant. The implant has an outer radius ( b 2) and a centered, tapered hole.[88] The tapered hole geometry is defined by the top ( rit ) and bottom ( rib ) radii and the depth ( Lh ). The abutment geometry is defined by the top and bottom radii ( rat ) and ( rab ), respectively. The implant engagement depth is defined as D = ( rit – rab )/tan θ.

The semicone taper angle θ is assumed to be the same for both components. The effects of taper angle mismatch Δθ between the components have been investigated theoretically and experimentally by Aguirrebeitia et al.[86,94] This section provides the analysis for the case of Δθ = 0. As a result of this assumption, when the abutment is placed in the implant with zero external force, the two surfaces will perfectly conform to one another. In this case, the bottom of the implant will be located at z = z[*] = ( r it – r ab)/tanθ. An axial displacement Δ z (measured relative to z[*] ) caused by an axially applied external force will cause interference between the two components with magnitude as follows: Fig 5-2 Schematic of the implant and abutment to describe the independent variables that influence the mechanics of the TIF connection. in the radial direction, as shown in Fig 5-2. Hence, the total length of the contact interface then becomes O’Callaghan et al[95] and Bozkaya and Müftü[93] analyzed the mechanics of a TIF connection by approximating the smooth tapered walls using a series of straight cylinders with changing radii and diminishing height. These solutions were based on the well-known formulation of the interference fit of two cylinders.[91] Consider the interference fit of cylinder 1, which has an outer radius b 1, with cylinder 2, which has a central hole with radius a and outer radius b . 2 2 If b 1 > a 2, the interference is defined as follows: δ = b 1 – a 2. The contact pressure P c caused by interference can be given by the following relationship: Fig 5-3 Free-body diagram to determine the expression of pull-out force. The equilibrium of the forces acting on the abutment when an axial insertion force F i (a) and an axial pull-out force Fp (b) is applied. A normal force caused by initial insertion N and a tangential force of magnitude ( µN ) act on the tapered wall. Note that N represents the resultant of the axisymmetric reaction forces. Note that equation (3) is valid if the material properties of the mating cylinders are the same (ie, E 1 = E 2 = E and v 1 = v 2 = v ).

In the case of a tapered fit, the outer radius of the abutment and the inner radius of the implant vary linearly along the z -axis as follows: The insertion force Fi , the pull-out force Fp , and the loosening torque TL are critical variables that contribute to the successful operation of TIF implant systems. In general, the approximate solution of the contact pressure distribution given in equation (5) helps develop closed-form relationships for these variables.

To find an expression for the pull-out force Fp , consider the free-body diagram of the abutment given in Fig 5-3, where the resultant contact force N (due to the initial interference), the pull-out force Fp , and the frictional force com- Fig 5-4 The magnitude of the loosening TL torque Fig 5-5 Insertion and pull-out forces based on Design-1 implant and abutment parameters ( D =1.5 mm) (a) and and the interfacial shear stress caused by friction deDesign-2 implant and abutment parameters ( D = 2.5 mm) (b) . See Table 5-1. (Solid/dashed lines, θ = 1; lines with termine the onset of abutment loosening. +, θ = 2; lines with circle, θ = 3)

um of the interference fit. The coefficient of static friction is ponent µsN are shown to contribute to the static equilibri- µs . An expression for the pull-out force is obtained by using the static equilibrium of the resultant forces:

An expression for the loosening torque can be obtained by examining the free-body diagram shown in Fig 5-4. Static equilibrium of the torque acting on the abutment then leads to the following relationship: The resultant contact force N , caused by the interference fit, can be obtained by integrating the contact pressure P c over the contact area along the tapered interface: This yields: The pull-out force of a TIF is then obtained by using equations (6) and (8): The insertion force Fi can be obtained by considering the equilibrium of forces acting on the abutment based on the free-body diagram of the abutment shown in Fig 5-3a. This results in the following relationship: which yields Equations (9), (10), and (11) show that seven independent parameters— E , Lc , b 2, rab , δ, θ, and µ— affect the insertion force, the pull-out force, and the loosening torque. The pull-out force increases linearly with δ and E , and it increases with ( L c)[3] . Similarly, the loosening torque increases with ( L c)[4] . These relationships point to the importance of a large contact surface at the IAI.

Figure 5-5 shows some representative calculations for the insertion and pull-out forces and the loosening torques for a range of implant and abutment parameters described in Table 5-1. The effects of the half-taper angle (θ = 1, 2, 3 degrees), the implant outer radius ( b 2 = 1 to 3 mm), and the implant engagement length ( D = 1.5, 2.5 mm) are investigated for rab = 0.7 mm. Both of these examples show that the insertion force is larger than the pull-out force. These calculations also show that for a large taper angle, it is harder to insert the abutment, yet easier to pull out, when compared with a small taper angle. For example, for the case of θ = 3 degrees, b 2 = 3 mm, and D = 1.5 mm, it takes about 850 N to insert an abutment and 600 N to remove it, whereas for the case of θ = 1 degrees, b 2 = 3 mm, and D = 1.5 mm, the insertion force is 780 N and the pull-out force is 700 N. These values indicate that abutments with smaller taper angles would be more stable in functional loading (all other parameters being equal). Fig 5-6 A comparison of efficiency trend predictions. Fig 5-7 Dependence trend of loosening torque values based on Design-1 implant and abutment parameters ( D Efficiency is only a function of the half-taper angle. = 1.5 mm) (a) and Design-2 implant and abutment parameters ( D = 2.5 mm) (b) . See Table 5-1.

A comparison of Figs 5-5a and 5-5b also shows that increasing contact area by considering longer contact lengths ( Lc ) causes an increase in both insertion and pull-out forces. Similarly, it is seen that increasing the implant radius b 2 causes the pull-out force to increase.

Efficiency (η) of a TIF is defined as the ratio of the pull-out force to the insertion force. This ratio was first defined by Bozkaya and Müftü[93] and was computed based on the energetic considerations. Aguirrebeitia et al[94] showed that the relationship derived by Bozkaya and Müftü[93] overpredicts the efficiency. In a recent study, Aguirrebeitia et al[94] developed the following relationship for the efficiency of the TIF connections: In obtaining this relation, they made use of the fact that the horizontal resultant force caused by interference would have to be constant during insertion and pull-out events. Here a similar formula, which assumes that the normal force N remains constant, is presented. By using equations (9) and (10), the following expression can be obtained: It is interesting to note that efficiency in either case is predicted to depend primarily on the half-taper/semicone angle θ. A comparison of the predictions is provided in Fig 5-6, which shows that both relationships predict the same trend with θ, but the efficiency prediction given by equation (13) is slightly higher than that predicted by equation (12).

Aguirrebeitia et al[94] also investigated the effects of mismatch (Δθ) of the taper angles of the abutment and the implant, and they showed a negligibly small effect caused by Δθ but a nonnegligible (though still small) effect caused by insertion force Fi . This is summarized in the following empirical relationship: The constants were obtained experimentally as follows: mFP = 6.136 × 10[–4] (Newton)[–1] , b = 168.68 Newton, and mΔθ = 4.099 × 10[–2] (deg.)[–1] .

The trends of dependence of loosening torque TL on b 2, LC, and θ are shown in Fig 5-7. In general, increasing the implant diameter b 2 , the contact area, and the taper angle θ causes an increase in the loosening torque. However, an increase in the loosening torque TL is not as strongly related to these parameters as in the case of pull-out force FP . It should be noted that other factors might affect loosening of an abutment, such as fatigue failure of the asperities at the contact interface or reduction of the effective friction coefficient due to the presence of saliva.

To corroborate the formulas presented above, Bozkaya and Müftü[3] used FEM to analyze the mechanics of the TIF. The predictions of the interference fit formula provided by equation (5) were compared with the results of the FEM analysis. Figure 5-8 shows a comparison of the contact pressure predicted by the simplified analysis presented in equation (5) and the more complete analysis provided by FEM.[3] The results of the comparison are in agreement in the central region of the interface, but the FEM analysis shows that contact pressure spikes would develop near the top and bottom edges of the interface. Fig 5-8 A comparison of the contact stress distribution as predicted by equation (5) and the FEM for an angle θ = 9 degrees, Lc / b 1 = 4, b 2/ b 1 = 3, and δ / b 1 = 16 × 10 b[–3] . The center of the graph shows the FE mesh used in the solution and the variation of the contact pressure with respect to the IAI.

Implant Macrogeometry

Macrogeometry is a term that describes an object’s overall size and shape.[96] For dental implants, macrogeometry tends to describe the length, width, and shape that the implant possesses. Dental implant macrogeometry is suggested to be an important factor involved in implant survival and success.[97,98] The overwhelming majority of modern implants are cylindric, freestanding structures that are intended to resemble a natural tooth (unusual shapes such as blades and corkscrews have also been used; see chapter 1). On these modern implants, there is usually some form of external structure (eg, threads, fins) that serves to increase the surface area of the implant and provide an anchorage site for regenerating bone. The most common type of implant macrogeometry is the screw-root form (SRF) implant. These implants possess external threads that are used to screw the implant into the osteotomy. While SRF design motifs are ubiquitous, they are not the only type of macrogeometry implemented by modern implants; another implant design motif is the finned, serrated, or plateaued implant. Plateaued implants, also known as plateau-root form (PRF) implants , possess a series of circular discs or fins that run along the axis of the implant body (Fig 5-9). A number of implants have utilized the PRF design motif, including Bicon implants. As shown in chapter 4, PRF implants create a unique microenvironment for the adjacent bone during early and long-term healing. The remainder of this chapter discusses PRF implants from an engineering standpoint, placing particular emphasis on load transfer and periimplant bone remodeling. Fig 5-9 Implant systems with PRF design motif. The PRF macrogeometry has been utilized by several implants over the past 20 years. (a) The DB Precision implant (DB; the antecedent to modern Bicon implants). (b) The Micro-Vent implant (Paragon). (c) The Omni R family implant (Tatum). (d) The Miter 2000 implant (Miter).

The development of PRF implants

The development of PRF implants provides an excellent example of how troubleshooting a design question in a stepwise fashion can obtain the best results. Work concerning PRF implants began at the Battelle Laboratory under the guidance of Thomas Driskell (see chapter 1). The initial implant designs investigated by Driskell and his team had very little in common with the macrogeometry seen in modern PRF implants, designed as loose approximations of normal teeth. The first implants Driskell tested possessed either single or bifurcated roots and were completely smooth. Driskell’s original hypothesis was that Sharpey’s fibers would attach to the smooth implants and secure them in the socket; however, after functional loading, all of Driskell’s early implant designs failed.[99] The next design investigated was a root structure that possessed a rough, porous surface. The rationale behind this implant design was that the growth of bone within the porous surface and asperities would serve as a means of stabilization. The rough, porous implant proved to be more successful than the previously tested smooth implant: After 9 months, the rough implants were found to be completely osseointegrated.[99] In an attempt to improve upon the new design, Driskell experimented with what he described as a “grooved or corrugated pattern,” the rationale being that such a pattern would provide more opportunities for bony ingrowth and increase the surface area, thus providing further anchorage by the surrounding bone.[99] After testing rough implants with and without grooved patterns, it was found that the latter was more successful. From the initial smooth implant to the finned appearance observed in modern Bicon implants today, Driskell used a stepwise approach to improve upon implant designs until the desired outcome was achieved.

Though Driskell was unaware of this at the time, the unique macrogeometry he had created was orchestrating a specific type of healing to take place around the implant: The addition of grooves permitted access to the osteogenic cells and growth factors responsible for de novo bone formation.[100,101] Briefly, the gaps created between the osteotomy wall and the fins of the implant created a space that allowed trabecular-like bone to form via an intramembranous-like healing process, a process different from the interfacial remodeling that occurs around SRF implants.[100–102] This space would later be named a healing chamber . The differences between SRF and PRF implants, as they pertain to early and long-term bone healing events, have been discussed in detail in chapter 4; however, from an engineering perspective, the way in which implant macrogeometry distributes stress and strain to the surrounding bone, along with how that bone responds to such loads, warrants further consideration.

Effect of implant macrogeometry on load transfer

Implants are confronted with the same occlusal forces as natural teeth, albeit in a different biomechanical environment. Unlike a natural tooth, an implant does not receive support from the periodontal ligament; instead, occlusal loads are transferred directly to the surrounding bone. Because the direction and magnitude of occlusal loads have pronounced downstream effects on bone remodeling—and hence implant survival—the manner in which dental implants transfer occlusal loads is of the utmost importance.

Implant macrogeometry is a major factor that influences occlusal load transfer from the implant to surrounding bone. Therefore, it is crucial to evaluate how the overall geometry of an implant system responds to stress and strain.[103] FEM is a powerful tool for investigating stress and strain distribution. Using FEM, the stress and strain response for implant characteristics such as overall size (eg, length, diameter), implant neck dimensions, and the effect of IAI style on peri-implant bone stress have been evaluated and discussed above.[60–63,103] Similarly, FEM has been used to predict the response of bone to different implant macrogeometries under a range of loads.

Bozkaya et al[103] examined increasing vertical and lateral loads on five commercially available dental implant systems that incorporated a variety of macrogeometries, including a PRF design (ie, a Bicon implant). The authors identified what they called a bone overload area : a region where the compressive and tensile strength of the bone had been exceeded by the principle stresses (ie, maximum compressive stress [170 MPa] and maximum tensile stress [100 MPa]).[103] While all five implants had similar bone overload values in the region where compact bone, trabecular bone, and the implant intersected, Bicon implants were shown to have no overload regions in the coronal-most portion of compact bone, a phenomenon that the authors attribute to the narrow sloping shoulder.[103] The conclusion by Bozkaya et al was significant because the coronal-most portion of compact bone is the recipient of most of the occlusal forces transferred via the implant.[103–109]

Interestingly, some authors have reported higher stress and strain distributions for PRF implants.[108,110] Chun et al[108] reported that when compared with the threads of SRF implants, the fins of PRF implants exhibited a much higher maximum effective stress to the surrounding bone when presented with an oblique load of 100 N. Based on their results, Chun et al[108] predicted that the distribution of stress around PRF implants would cause bone resorption and decrease the binding force between the bone and the implant. Chun et al[108] concluded that when screw pitch decreases and implant length increases, maximum effective stress decreases. Nevertheless, other authors have predicted positive peri-implant bone remodeling outcomes for PRF implants; furthermore, these positive outcomes have been corroborated by histologic examination in both animals and humans.[60,64,100–103,108,111–113]

Effect of implant macrogeometry on periimplant bone remodeling

Bone is a dynamic tissue that is constantly undergoing remodeling. Mechanical stress, strain, and strain energy density are major factors responsible for inducing bone-remodeling events. Through mechanotransduction, cells forming basic multicellular units (BMUs) repair bone and alter bone density in response to stimuli (see chapter 4). In the context of dental implants, occlusal forces are transmitted through the implant and into the surrounding bone, where BMUs then perform their remodeling activities. Thus, the way in which an implant transmits the stress and strain of occlusal forces to the surrounding bone is important from both a clinical and an engineering perspective.

Stress and strain

As mentioned above, FEM is a powerful tool for investigating stress and strain distribution. FEM has been used successfully to model bone density distribution and bone remodeling around dental implants.[60,114–119] Chou et al[64] used Fig 5-10 Equivalent strain distribution of a long, narrow implant (3.5 × 11.0–mm) and short, wide implant (5.0 × 6.0–mm) inserted at different depths in high-quality alveolar bone (a) and low-quality alveolar bone (b) . Strain level is measured in a range from 0 to 3,000 με, with lower values indicated in blue and higher values indicated in red. Overstrain is indicated as gray.

FEM to evaluate the biomechanical response of peri-implant bone to two different sizes of Bicon implants (a 3.5 × 11.0– mm long, narrow implant and a 5.0 × 6.0–mm short, wide implant) and at different insertion depths. Additionally, because bone quality will undoubtedly vary on a patient-by-patient basis, the authors examined strain distribution in the context of both poor- and high-quality alveolar bone.[64] Chou et al[64] measured the strain in surrounding bone in accordance with the thresholds suggested by the mechanostat hypothesis, with values ranging from 0 to 3,000 με.[120] Prolonged exposure to internal strain levels ranging from 0 to 200 με are predicted to result in low bone density; strain levels ranging from 200 to 1,000 με are considered in equilibrium; strain levels ranging from 1,000 to 3,000 με are predicted to stimulate bone remodeling (and thus result in increased bone density); and finally, strain levels over 3,000 με are predicted to produce stress fractures in the bone.[64,120]

Chou et al[64] determined that when short Bicon implants were placed in high-quality alveolar bone, the distribution of strain was predicted to keep bone-remodeling events in a state of equilibrium around most of the implant (strain levels ranging from 200 to 1,000 με), with a small region predicted to stimulate bone remodeling toward the apex of the implant (strain levels ranging from 1,000 to 3,000 με).[120] The long Bicon implants had similar results as the short implants; however, there was a larger region of higher strain reported at the apex of the implant[64] (Fig 5-10a).

In areas of low-quality bone, the distribution of strain for both implant sizes was shifted to higher levels. Overall higher strain was predicted around both implants and at the periphery[64,120] (Fig 5-10b). While the lower portion of both implants had strain levels ranging from 1,000 to 3,000 με, the apex of the implants registered the highest levels of strain—with some locations reporting overstrain, especially in the long implants.[64,120] However, for both high- and low-quality bone, higher levels of strain could be converted to more favorable levels by altering the insertion depth.[64]

The results presented by Chou et al[64] demonstrate that implant length, insertion depth, and bone quality all play an enormous role in how peri-implant strain is distributed. The authors conclude that in general—and as is the case for most implants—the majority of the strain was transferred to a localized area of the alveolar ridge. Additionally, when compared with the 3.5 × 11.0–mm implant, the 5.0 × 6.0– mm implant generated strain more evenly around its perimeter. For both implants, there was higher strain at the tips of the fins with less strain in the healing chambers[64] (see Fig 5-10). Finally, it was found that implant insertion levels caused the strain levels to vary, and in cases of poor bone, overstrain could be prevented by changing the insertion depth.[64]

Peri-implant bone remodeling

In another study by Chou et al,[60] FEM was used to predict peri-implant bone remodeling around Bicon implants and four other implant designs. Curious about homeostatic bone-remodeling events taking place during the maintenance phase of peri-implant bone remodeling for implants with different macrogeometries, Chou et al[60] used a unique bone-remodeling algorithm in concert with FEM to make bone-remodeling event predictions for five different implant design motifs after placement in extraction sockets. During their analysis, Chou et al[60] examined three long implants (3.5 × 11.0–mm) and two short implants (5.0 × 5.0– and 5.0 × 5.4– mm). Based on the various mastication forces exerted by individuals, the authors chose to evaluate three different levels of loading force (100 N, 300 N, and 500 N), all applied to the crown at an 11-degree angle for 100 iterations.[60] Figure 5-11 shows a summary of the elastic modulus distribution around the five implant design motifs. Based on values reported in the literature, the elastic modulus of cancellous bone was set as 2 GPa, and cortical bone was set as 13.7 GPa.[60,121,122]

At zero iterations, all five implants presented an elastic modulus distribution similar to that seen for a natural tooth. After loading at 100 iterations, changes to peri-implant elastic modulus were observed and influenced by implant macrogeometry. For the three long implants, at 100 iterations with a force of 100 N, bone remodeling was observed at the apex, as indicated by the higher elastic modulus. For the short implants tested at 100 N, a more natural loading environment appeared to be present (see Fig 5-11). Interfacial bone loss was also predicted near the coronal part of all of the long implants (indicated by the white-colored region); however, as loads increased, only long implants nos. 1 and 2 showed a corresponding increase in bone loss.

The short implants experienced a more localized remodeling that was restricted to the perimeter of the implant and reported bone density distributions similar to that of the natural tooth.[60] Most importantly, the short implants did not experience the type of interfacial bone loss seen around the long implants. From their results, Chou et al[60] reached the conclusion that short implants were better suited to prevent bone loss at high occlusal loads and conserve the natural mechanotransductive signaling environment.

Summary and Outlook for the Future

This chapter has reviewed the clinical and design-related factors that influence the success of dental implant systems using tapered abutments and a PRF design motif. The literature survey has shown that a tapered interface IAI provides a significant improvement over butt-jointed, screw-retained abutment systems where microbial leakage is concerned; this is in part attributed to the ability of tapered systems to deliver higher contact pressure to the IAI. Another important factor has been the improved resistance provided by the tapered abutments to bending, which otherwise would lead to microgaps at the IAI. In fact, the overall stability of the tapered abutments is attributed to a stiffer joint region necessitated by the tapered interface. This stiffness in turn helps minimize axial and lateral motion of the implant during function, preventing unnecessary bone trauma; accordingly, several studies suggest that bone resorption around conical abutments is less likely. In addition, the literature survey suggests that the effect of the surface roughness along the tapered interface should be systematically investigated. Considering that all surfaces are rough and contact is established on the tops of the asperities, perfect sealing against bacterial invasion would depend on the surface asperity heights, density, and contact pressure. Fig 5-11 Elastic modulus distribution of bone around five different implant design motifs. Three long implants (3.5 × 11.0–mm) and two short implants (5.0 × 5.0–mm and 5.0 × 5.4–mm) were tested. The top row shows the E (GPa) at zero iterations, and the following three rows show E (GPa) at 100 iterations for 100 N, 300 N, and 500 N, respectively. The implants labeled “Long 2” and “Short 1” are 3.5 × 11.0–mm and 5.0 × 5.0–mm Bicon implants, respectively.

In light of recent experimental work, the authors have developed a new expression for the insertion force and the interface efficiency (the ratio of the pull-out force to insertion force). The work presented here has shown that, for the range of parameters considered, an abutment with a smaller taper angle requires a relatively smaller insertion force than an abutment with a larger taper angle. However, the opposite was found to be true for the pull-out force; that is, it is relatively easier to pull out an abutment with a large taper. Smaller taper angles seem to be more efficient from an axial force perspective. Where loosening torque is concerned, analysis has shown that the differences between the three taper angles considered here are relatively small. Nevertheless, the loosening torque for a smaller tapered interface is slightly higher.

Finally, we have examined the macrogeometry of PRF implants with a focus on their development and the distribution of stress and strain to surrounding bone. Furthermore, we have examined FEM predictions of peri-implant bone remodeling around Bicon implants and implants possessing an SRF design motif. FEM predicts that short implants incur less interfacial bone loss to adjacent bone than long implants when placed in extraction sockets, and varying the insertion depth can influence how strain is distributed into peri-implant bone. In conclusion, based on clinical and design perspectives discussed here, the use of short implants with tapered abutments seems to be a natural choice for long-term overall success of dental implant systems.

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110. Patra AK, DePaolo JM, D'Souza KS, DeTolla D, Meenaghan MA. Guidelines for analysis and redesign of dental implants. Implant Dent 1998;7:355–368.

111. Coelho PG, Marin C, Teixeira HS, et al. Biomechanical evaluation of undersized drilling on implant biomechanical stability at early implantation times. J Oral Maxillofac Surg 2013;71:e69–e75.

112. Gil LF, Suzuki M, Janal MN, et al. Progressive plateau root form dental implant osseointegration: A human retrieval study. J Biomed Mater Res B Appl Biomater 2015;103:1328–1332.

113. Huang B, Meng H, Zhu W, Witek L, Tovar N, Coelho PG. Influence of placement depth on bone remodeling around tapered internal connection implants: A histologic study in dogs. Clin Oral Implants Res 2015;26:942–949.

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06

The Influence of the Implant-Abutment Interface on Peri-implant Health

Giorgio Lombardo | Jeffrey Lehrberg | Jacopo Pighi | Joseph Leary | Peter Chaloupka | Mauro Marincola

Modern dental implants are typically composed of two parts: the implant and the abutment. The location where the implant and the abutment join is called the implant-abutment interface (IAI). The IAI must be stable to withstand the forces frequently encountered in the mouth. There have been numerous IAI styles adopted over the years, and although these designs were created with a primary focus on stability and abutment retention, it has been revealed that IAI design also has the potential to influence bacterial infiltration into the inner spaces of the implant and from there into the surrounding peri-implant tissues—consequently influencing the development and progression of peri-implant pathologies. This chapter reviews common IAI design strategies along with peri-implant pathologies and their associated microorganisms; furthermore, recommended treatments for peri-implant diseases are discussed.

IAI Design Strategies

While there have been many implant-abutment interface design strategies implemented in dentistry, three designs stand out in particular as being the most frequently used: the Morse taper; screw-retained or screw-in; and screw-retained tapered, screw-in tapered, or taper-integrated screw (TIS) (Fig 6-1).

Locking taper

A detailed explanation of locking tapers can be found in chapter 5. Briefly, a lockingtaper abutment relies on cold welding at the IAI to produce a secure connection. Cold welding is the process whereby asperities on the joining surfaces of the imor taper-integrated screw (TIS) abutments . TIS systems incorporate designs from both the Morse taper and screwretained abutments inasmuch as they posses both a short series of threads and a tapered portion. Although the inclusion of a Morse taper in the TIS system provides a much tighter surface-to-surface contact (which eliminates multiple problems found in the screw-retained system), it still utilizes a short-threaded connection as its primary mode of stability, which is susceptible to loosening. Because TIS systems possess a Morse taper, they are often grouped with locking-taper systems when evaluating bacterial contamination across the IAI; this has led to a misconception about the efficacy of Morse taper systems as a barrier to bacterial contamination, as shown later in this chapter. plant well and abutment post coalesce (albeit at ambient temperatures) as a result of high pressure.[1,2] A Morse taper consists of a cone-shaped male end or shank of a given taper angle that is inserted into a female receiver with an equal taper angle. The angle of the IAI taper influences its properties. Based on the total angle of the taper, Morse tapers can be self-releasing (eg, semicone angles greater than 7 degrees) or locking taper (eg, semicone angles less than 7 degrees and typically below 2 degrees). The semicone taper angle for the Bicon IAI is 1.5 degrees, thus making it a locking taper (also sometimes referred to as possessing a tapered-interference fit [TIF]). Fig 6-1 Three common IAI designs. (a) Locking taper. (b) Screw-in or screw-retained. (c) Screw-in/Morse taper, screw-retained tapered, or TIS.

Screw-in

By far the most ubiquitous IAI design strategy is the screw-retained abutment design, or screw-in system. Screw-retained abutments can be either internal or external hex-type—names derived from both the shape of the coronal portion of the implant and the tool required to fasten them. A perceived benefit of screw-retained abutments is that they allow the prosthesis to be easily retrieved; however, three drawbacks are the requirement of a hole in the crown (needed for screw placement and retrieval), the possibility of screw loosening and fractures, and a lack of flexibility in positioning.

Screw-retained taper

IAI designs that incorporate both a Morse taper and a screw are known as screw-retained tapered abutments ,

Morse taper, screw-retained, and TIS abutments all have their vocal proponents and detractors, each possessing a wealth of data on why a given system might be superior. While the individual IAI designs mentioned above may possess unique advantages and disadvantages in a given clinical scenario, the next section of this chapter focuses solely on how IAI design relates to the movement and subsequent contamination of bacteria in and around the implant microenvironment.

Microbiota of the Human Mouth and Peri-implant Pathology

The human mouth contains multiple microhabitats (eg, the gingival sulcus, tongue, teeth), and each harbors its own unique ecologic assemblage of microorganisms.[3] Over 750 bacterial taxa have been identified in the human mouth, and it is hypothesized that these represent less than 50% of the organisms that make up the total oral microbiome.[3,4] Oral microorganisms exist in polymicrobial communities called a biofilm , which coats the surface of host tissues.[4] In normal, healthy human mouths, the microbiota exist in a state of commensalism with their host.[4] However, in cases of disease, pathogenic communities work in concert to shift the relationship from one of commensalism to one of parasitism.[4]

A number of bacterial species have been implicated in peri-implantitis and/or periodontal disease. As shown in Table 6-1, a majority of the bacteria associated with disease states favor the anaerobic and/or microaerobic conditions that certain oral microhabitats present (eg, gingival sulcus and internal implant wells or bores). Therefore, the geometry and design of some implant systems offer excellent hiding places for deleterious bacteria (making their eradication difficult) and provide conditions conducive to their propagation; moreover, the architecture of certain IAIs can actively disseminate deleterious bacteria, infecting otherwise healthy peri-implant tissues.

Two of the most common and well-studied pathologies present in the field of implant dentistry are peri-implant mucositis and peri-implantitis, which, depending on the criteria used, have an incidence ranging from 11.3% to 63.4% and 18.8% to 51.9%, respectively.[5–7] Peri-implant mucositis and peri-implantitis are similar and have many overlapping symptoms, including inflammation, gingiva sensitivity, bleeding upon probing, and purulent exudate. The main difference between them is that bone is not affected in peri-implant mucositis.[8,9] In many ways, the symptoms of peri-implant mucositis and peri-implantitis share similarities with gingivitis and periodontitis, disease conditions of natural teeth.[10,11] Peri-implant mucositis has been defined as the reversible inflammation of the mucosa adjacent to the implant without damage occurring to the surrounding bone.[12,13] Peri-implantitis is defined as the irreversible inflammation of both the mucosa and bone surrounding the implant and is characterized by crestal bone loss. However, as shown below, referring to peri-implantitis as irreversible may be overstated; more accurately, peri-implantitis is irreversible only to the extent of our present inability to fully and predictably regenerate the entirety of bone under conditions where the peri-implant pathology progresses unmanaged.[12,13] When a locking-taper IAI is present, it eliminates an avenue of bacterial contamination; the modalities presented here can effectively manage peri-implantitis and restore a good deal of the bone loss incurred.

While the etiology of peri-implant mucositis and periimplantitis has still not yet been fully determined, it is generally accepted that the accumulation of deleterious bacteria (acting either as a primary or secondary etiologic factor) into the peri-implant microenvironment plays a major role in the progression of these diseases.[12] Because of their involvement in peri-implant disease states, preventing deleterious bacteria from accumulating in peri-implant microenvironments is crucial. IAI design strategies that take steps to minimize the potential hiding spaces and pathways for microorganisms can reduce—if not eliminate—their unchecked leakage into both the implant and peri-implant tissues, thus reducing the possibility of peri-implant diseases developing or progressing.

Given the association between known periodontal pathogens and the development of peri-implantitis, some clinicians use systemic antibiotic therapy in conjunction with traditional scaling and root planing to treat periodontal disease prior to placing implants. To identify the appropriate antibiotics, microbial samples are obtained from periodontal pockets suspected to have periodontal disease involvement. Follow-up bacterial testing can be used to determine antibiotic effectiveness and to monitor for recurrence of infection.

Microgaps and Micropumps at the IAI

A primary route of bacterial infiltration into the implant system—and the subsequent dissemination of bacteria into peri-implant tissues—occurs at microgaps, and through the

Microorganisms associated with peri-implant Table 6-1 pathology action of micropumps, at the IAI.[14–21] When occlusal stresses are applied to the prosthesis, the compressive forces deform the threaded interface and create small gaps (called microgaps ) between the implant and the abutment.[22] These microgaps produce a communication between the periimplant microenvironment and the implant well, affording bacteria the opportunity to colonize and creating a reservoir of deleterious microorganisms and endotoxins[15,16,21,22] (Fig 6-2). Additionally, Zipprich et al[22] demonstrated with

Fig 6-2 Microgaps at the IAI allow bacteria to colonize the internal spaces of an implant, creating a reservoir of deleterious microorganisms and endotoxins. (a) The locking-taper IAI creates a bacterial seal. (b) Microgaps inherent in a screw-in IAI design provide access to deleterious bacteria.

Mm Table 6-2 Assessing bacterial leakage at the IAI

(continued)

Table 6-2 (cont) Assessing bacterial leakage at the IAI HI, internal hexagon.

high-speed radiographs that the pressure and volumetric changes that occur during the act of mastication have the potential to generate micropumps, forcing bacteria out of the implant well and into the adjacent tissues.[17,20] As potential reservoirs and disseminators of disease-causing organisms, microgaps and micropumps represent a major problem for any implant system. Therefore, to be successful, an implant system must reconcile the need for implant-abutment stability and user-friendliness for the clinician but also minimize or eliminate the presence of microgaps at the IAI.

Analysis of bacterial leakage across the IAI of different implant systems has yielded wide-ranging and inconsistent results.[14,15,23–33] The simplest approach for measuring bidirectional leakage in an implant-abutment system typically involves in vitro tests where the implant system is submerged into a solution containing either dye or bacteria. Microleakage (indicated by bacterial growth or dye contamination) is then observed either in the implant well (known as outside-in experiments ) or in the surrounding solution (known as inside-out experiments ). The typical bidirectional leakage experiments used to test the IAI are not ideal, as the potential for contamination by bacteria in the environment and on the researchers is an ever-present concern even under the best conditions.[34]

The data presented in Table 6-2 provide a mere glimpse at some of the many in vitro tests that have been performed assessing microleakage at the IAI. Table 6-2 depicts percent leakage and type of bacteria tested at the IAI as it relates to IAI design strategy. The variation of percent leakage illustrates the effect that both experimental design and Fig 6-3 SEM images showing an assembled abutment and implant after bidirectional leakage test. (a) Side view showing the abutment on the left and the implant on the right. (b) Coronal view of the same implant. Scale bar = 1 mm.

Fig 6-4 SEM image showing part of the IAI. The gap between the implant and the abutment is less than 0.5 µm. Scale bar = 1 µm.

the experimenter may have on the subsequent results. For example, the same implant (ie, manufacturer and system) in the hands of different investigators produced leakage values that range from 0% to 95%.[15,23,27,35] Possible explanations for the disparity seen in leakage at the IAI range from experimental design flaws to imprecise machining on the manufacturing end.[23,35]

It has been hypothesized that a locking-taper implant-abutment connection reduces, if not eliminates, the presence of microgaps at the IAI.[14,15,22,33,36,37] In theory, a locking-taper IAI will create a hermetic seal as a result of cold welding that occurs between the abutment and implant; whether or not a complete seal is formed along the entire circumference of the implant well and abutment is influenced by the machining of the parts and the angle of taper.[15,38,39]

There is a tendency to combine all implant systems that possess a Morse taper at the IAI into one category; it is important, however, to differentiate locking tapers as special subtype of Morse taper and evaluate them separately.[16,27,34,40,41] When viewed in their own context (ie, when not combined with TIS systems or other wide-angle Morse taper systems), locking-taper designs appear to be more successful at preventing microleakage at the IAI[15,16,23,33,34,41] (see Table 6-2). The disparate leakage rates reported for Morse tapers in Table 6-2 highlight the importance of distinguishing the different subtypes of Morse tapers (ie, locking tapers from TIS systems). TIS designs utilize a Morse taper to act as a barrier to microleakage and bacterial colonization of the internal implant spaces. Unfortunately, however, the tightening torque of the screw can create a misfit between TIS components, creating a gap that permits leakage. Moreover, as this torque increases, so does the corresponding degree of misfit between components and the ensuing bacterial contamination[16,42,43] (see chapter 5).

Analysis of the Bicon IAI

The integrity of the Bicon IAI has been analyzed using multiple methods, including standard bidirectional leakage tests, scanning electron microscopy (SEM), and threedimensional x-ray microtomography (microCT).[15,40,44] The tests that have been performed thus far on the bacterial sealing capacity of the Bicon IAI are promising and support the hypothesis that a bacterial seal is present at the IAI that excludes bacteria from the implant well.

Dibart et al[15] evaluated the bacterial seal of the Bicon IAI by performing a set of outside-in and inside-out bidirectional leakage tests (Fig 6-3). Using a broth containing a mixture of the well-established periodontal pathogens Aggregatibacter actinomycetemcomitans , Fusobacterium nucleatum , and Streptococcus oralis , the authors tested for bacterial contamination in the implant well and surrounding media (ie, outside-in and inside-out, respectively).[15] In both bidirectional leakage tests, there was no evidence of contamination during the time period tested (ie, 0% contamination).[15] Following their bidirectional leakage tests, Dibart et al[15] used SEM to examine the implant-abutment assemblies; in their examination, the authors reported a complete absence of bacteria in the wells of the implants. Although bacteria were present on the exterior surfaces of the implant and abutment, they were absent from all the internal implant spaces below the location of the metal-to-metal cold weld—200 µm below the crevice formed between the implant chamfer and abutment post[15] (Figs 6-3 to 6-8).

In the SEM assays of the IAI, Dibart et al[15] noted a gap at the coronalmost region that was approximately < 0.5 µm (see Fig 6-4); however, the authors concluded that this gap was too small to permit the infiltration of the bacterial species tested (ie, A actinomycetemcomitans [0.4 × 1.0 µm]; F nucleatum [3.0 × 0.4 to 10.0 × 0.7 µm]; and S oralis [< 2.0 µm in diameter]). Based on the size of the gap—along with the absence of bacteria in the implant well and lack of contamination from the bidirectional leakage studies—the authors concluded that a complete bacterial seal had indeed been created.[15]

The results presented by Dibart et al[15] support the claim that a complete bacterial seal may be present at the Bicon IAI; nevertheless, some studies have brought this into question.[23,35] An inside-out bidirectional leakage test was used to compare Bicon implants and a TIS implant system, and it was found that both systems experienced contamination Fig 6-5 SEM image showing the abutment after removal from the implant. (a) The white box indicates the location of the cold weld. The white arrow indicates a mark left by the forceps during removal. Scale bar = 1 mm. (b) A magnified view of the abutment post (box shown in a ). Bacteria and debris are absent from below the cold weld. Scale bar = 10 µm. Fig 6-6 SEM image showing the coronal chamfer present at the opening of the implant well. (a) The coronal chamfer is 120 µm in width. (b) Closer view of the coronal chamfer. Scale bar = 100 µm. Fig 6-7 SEM image of bacteria on the coronal chamfer. Bacteria did not penetrate the implant well (upper left corner) . Scale bar = 10 µm. Fig 6-8 SEM image showing the implant well after removal of the abutment. The implant well is free of bacteria. Scale bar = 100 µm.

(albeit at a low level). Of the ten samples tested, only two showed bacterial contamination[23] (see Table 6-2). Similarly, contamination of Bicon implants was found in a series of invivo experiments.[35] A possible cause of the contamination reported in these studies is inadequately seated abutments: The TIF used to secure the abutment to the implant relies on high pressure generated at the conical interface when inserting the abutment (see chapter 5). A gap in the IAI would interfere with the overall retention of the abutment in the implant and its ability to create a bacterial seal. A caveat to this, however, is that creating a perfect seal is a function of the surface roughness where the abutment and the implant are joined; bacterial contamination is possible if the joining surfaces are exceedingly rough.[18,45]

In addition to bidirectional leakage tests and SEM, another tool used to evaluate the IAI of implant systems is microCT scanning.[34] MicroCT scanning is a high-powered version of conventional computed tomography (CT scan) methods. MicroCT scanning allows for the nondestructive detection and analysis of objects (~8.0 µm in size). Traditional methods for visualizing objects under high magnification involved preparations that required harsh or destructive treatments and yielded an incomplete two-dimensional image. In contrast to traditional methods, microCT scanning allows for three-dimensional visualization of a sample without the need for destructive pretreatments.[46] MicroCT scanning has been used to investigate the IAI of locking-taper (ie, Bicon) and TIS implants (ie, Ankylos [Dentsply] and Straumann). It was found that in addition to having no observable microgaps, the Bicon IAI had the highest implant-abutment contact surface area of the three implants tested.[44,47] In addition to published data, the fact that bone gain and growth have frequently been demonstrated over Bicon’s IAI is logical evidence that the IAI is bacterially sealed.

Prevalence and Clinical Presentation of Peri-implant Disease

In addition to implant IAI design, other factors play a role in the etiology and progression of peri-implant diseases and the conversion of peri-implant mucositis to peri-implantitis, including overall patient health and prosthetic characteristics.[48–50] The accumulation of plaque and colonization of deleterious bacteria in the peri-implant environment has been suggested as being responsible for the pathogenesis of peri-implant disease.[6,12,51–57] Furthermore, inadequate patient hygiene has also been implicated as a contributing factor to the disease’s development and progression.[6] Accordingly, the first line of defense against peri-implant disease is meticulous patient home care. Likewise, clinicians must provide consistent, ongoing maintenance and monitoring and be prepared to intervene with existing therapies if peri-implant diseases do develop. The remainder of this chapter presents therapies that have proven successful in the treatment of peri-implant disease. Owing to conflicting definitions and varying inclusion/exclusion criteria, the frequency of peri-implant disease is highly variable. Reports assessing the prevalence of peri-implant disease range from 1% to 63.4%.[24,49,56–59] Reporting criteria notwithstanding, it is clear that of the two peri-implant diseases, peri-implant mucositis is more common, with a prevalence rate of 80% of patients and 50% of implants.[13,57,60]

Peri-implant mucositis presents with swelling and inflammation of mucosa surrounding an implant site. The most important indicator of peri-implant mucositis is bleeding upon gentle probing (ie, < 0.25 N) and/or suppuration.[57] Mucosal recession has also been observed in cases of peri-implant mucositis.[5] Unlike peri-implantitis, peri-implant mucositis does not involve bone loss beyond the normal remodeling that occurs following an implant procedure.

Treatment of peri-implant mucositis should begin early and aggressively to prevent its conversion to peri-implantitis. A study by Costa et al[61] showed that for patients who adhered to therapeutic guidelines, the rate of conversion of peri-implant mucositis to peri-implantitis was 18%.[48] However, for patients who did not adhere to therapeutic guidelines, the rate of conversion of peri-implant mucositis to peri-implantitis was 43.9%.[48,61]

Peri-implantitis has a prevalence rate that ranges from 20% to 56% of patients.[56,57,60] Like peri-implant mucositis, peri-implantitis presents with swelling, inflammation, and bleeding upon probing; however, a major difference that distinguishes peri-implantitis is bone loss.[56,62] As previously mentioned, peri-implantitis has been defined as irreversible. Although current treatments for peri-implantitis may fail to achieve restitutio ad integrum , there is a wealth of evidence showing positive outcomes from both nonsurgical and surgical modalities.[56,60,62]

Current Strategies for Treating Peri-implant Disease

The relationship between peri-implant mucositis and peri-implantitis has been compared with the relationship between gingivitis and periodontitis.[63] As is the case with gingivitis, peri-implant mucositis is roundly considered a treatable and reversible form of inflammation, provided that appropriate treatment modalities are pursued such as professional plaque removal and patient home care (eg, flossing).[48] Unfortunately, many conventional implant prosthesis designs (ie, TIS systems) often preclude the implementation of adequate home-care procedures by preventing mechanical cleaning of the site; furthermore, while the prosthetic crown of such conventional implant systems can be removed to facilitate submucosal debridement, this solution is typically unacceptable to patients.[64]

When removal of the crown and mechanical cleaning of dental plaque from the implant’s surfaces has been performed in concert with adjunctive anti-infective treatments (ie, local antiseptics, local/systemic antibiotics, and air-abrasive devices), it has resulted in limited short-term clinical improvements; however, this type of treatment has thus far never resulted in the complete resolution of peri-implant mucositis.[65] In the majority of cases, complete resolution of peri-implant mucositis is not feasible following a single treatment session; repeated treatments are necessary for complete resolution. Additionally, the discomfort felt by patients during mechanical debridement of the peri-implant sulcus further decreases their level of compliance with future procedures.

To minimize patient discomfort, less invasive protocols are recommended, such as a 10-week course of purely antiinfective measures to prevent recolonization of bacteria. Positive outcomes have been achieved using repeated subgingival administrations of an antiseptic, hygroscopic desiccating solution for the treatment of peri-implant mucositis around Bicon implants. Furthermore, there have been positive outcomes in the treatment of peri-implantitis by decontaminating infected sites using air powder abrasion followed by an antiseptic hygroscopic desiccating solution, and then augmenting intrabony defects using biphasic calcium sulfate combined with inorganic bovine bone material[66] (see chapter 16). The following treatments illustrate the aforementioned modalities used to treat patients with Bicon implants who are suffering from peri-implant disease. Fig 6-9 (a) Periapical radiograph showing bone loss around implants in the maxillary left premolar positions. (b) The bony defects around the implants are revealed after raising a full-thickness flap. (c) Palatal view showing a Class 1d defect on the implant in the second premolar position. (d) Decontaminating the surface of the implant using a hygroscopic desiccating solution. (e) Debridement of the infected site using low-abrasive air powder. (f) The defect is filled with bovine bone mineral mixed with synthetic biphasic calcium sulfate, along with adjunct antiseptics. (g) A primary, tension-free flap closure is recommended, using a periosteal incision to mobilize the flap if necessary. (h) Postoperative radiograph confirms the filling of the bony defect. (i) The 1-year follow-up radiograph shows the near complete filling of the bony defect. (j and k) Buccal and palatal views of the patient’s soft tissues 2 years after surgery. (l) A 5-year follow-up radiograph depicting the stability of the peri-implant bone.

Treatment 1

A 62-year-old man presented with pain and suppuration of the implant in the maxillary left second premolar position 1 year after prosthetic loading. A periapical radiograph revealed peri-implant bone loss affecting this implant as well as the adjacent one in the first premolar position and a failed endodontic treatment of the first molar (Fig 6-9a). Clinical examination revealed the presence of high probing depths between these implants (a 9-mm probing depth measured with a 10-mm periodontal probe).

An incision of the sulcus was performed, a full-thickness flap was raised to expose peri-implant bone defects, and the first molar was extracted (Fig 6-9b). Buccal and palatal views showed the presence of a Class 1d (Schwarz classification) defect on the implant in the second premolar position (Fig 6-9c). After defect degranulation, surface decontamination was accomplished by applying a desiccant (Hybenex, EPIEN) on the implant surface, followed by debridement with low-abrasive air powder (Figs 6-9d and 6-9e). After decontamination procedures, the bone defects were filled with deproteinized bovine bone mineral mixed with synthetic biphasic calcium sulfate (BondBone, MIS Implants Technologies), along with adjunct antiseptics (Fig 6-9f). No membranes were applied to cover the grafting material. It is recommended that primary, tension-free closure be made; if allowed, a periosteal incision to mobilize the flap is recommended (Fig 6-9g). A final radiograph was taken to confirm the filling of the defects (Fig 6-9h).

Intraoral radiographs taken at the 1-year follow-up revealed the almost complete filling of the defect, and the resolution of the patient’s peri-implantitis was confirmed by the absence of peri-implant pathologic probing (Fig 6-9i). Two- and 5-year follow-up radiographs and clinical photographs confirm the stability of the patient’s peri-implant soft tissue and bone (Figs 6-9j to 6-9l). Fig 6-10 (a) Peri-implant inflammation around the implant in the mandibular right first molar position 10 months after prosthetic loading. (b) Radiograph showing peri-implant vertical bone resorption on the distal side. (c) The crown is removed prior to surgery. (d) Raising the full-thickness flap reveals a Class 1e, crater-like peri-implant bone defect. (e) Following degranulation, the desiccating agent is applied. (f) The desiccating agent is left in situ for 1 minute. (g) The site is debrided mechanically using low-abrasive air powder. (h) The bone defect is filled with augmentation material. (i) The membrane is stabilized. (j) Primary tension-free closure is achieved. (k) A postoperative radiograph verifies that the defect has been filled with bone mineral. (l) A transmucosal Healing Abutment is inserted 4 months after surgery. (m) The original restoration is reinserted. (n) Radiograph following reinsertion of the original restoration. (o) One year after surgery, probing depths register at 4 mm, and there is no inflammation. (p) The 4-year follow-up radiograph reveals that the bone defect has been completely regenerated.

Treatment 2

A 40-year-old man presented with clinical signs of periimplant inflammation surrounding the implant in the mandibular right first molar position, which had been under prosthetic loading for 10 months (Fig 6-10a). A radiograph revealed peri-implant vertical bone resorption on the distal side of the implant (Fig 6-10b). Following the removal of the restoration, a full-thickness flap was elevated, which exposed a 3-mm Class 1e defect (Figs 6-10c and 6-10d).

The defect was degranulated, followed by decontamination with a desiccant (Fig 6-10e). The desiccating agent was left in situ for 1 minute and then washed away with a saline solution (Fig 6-10f). Next, the site was debrided with low-abrasive air powder (Fig 6-10g). The bone defect was filled with bone substitutes and covered with a resorbable membrane

(Figs 6-10h and 6-10i). Following membrane stabilization, a primary tension-free closure was made, and the implant was left to heal (Fig 6-10j). A postoperative radiograph was taken to verify that the defect had been adequately surrounded by bone mineral (Fig 6-10k).

Four months after surgery, the implant site was reopened, and a transmucosal Healing Abutment was inserted (Fig 6-10l). Two months later, the Healing Abutment was removed, and the original restoration was reinserted (Figs 6-10m and 6-10n).

One year after surgery, the probing depth registered at 4 mm without any signs of inflammation (Fig 6-10o). The regeneration of the peri-implant bone defect was confirmed via periapical radiograph (Fig 6-10p).

several other known protocols that aid in the successful regeneration of bone around Bicon implants; furthermore, research continues to determine which of these successful procedures is the most consistently effective.

References

1. Messler RW. Principles of Welding: Processes, Physics, Chemistry and Metallurgy. New York, NY: Wiley; 1999.

2. Bowden FP, Young JE. Friction and adhesion of clean metals. Nature 1949;164:1089–1090.

3. Dewhirst FE, Chen T, Izard J, et al. The human oral microbiome. J Bacteriol 2010;192:5002–5017.

4. Jenkinson HF, Lamont RJ. Oral microbial communities in sickness and in health. Trends Microbiol 2005;13:589–595.

Conclusion

The prevention of implant-related pathologies such as peri-implant mucositis and peri-implantitis is of primary concern for both patients and clinicians. Our recent understanding of the oral microbiome has revealed how bacterial communities can influence implant-related disease conditions; therefore, clinicians may want to preoperatively identify specific antibiotics to eliminate or reduce deleterious bacteria before placing implants. Reducing access of harmful bacteria to the inner spaces of the implant is also crucial. Preventing the infiltration and colonization of bacteria in the inner spaces of an implant can be achieved through IAI designs that use a locking taper; moreover, a locking-taper IAI design may also minimize the incidence of implant-related pathologies.

The Bicon implant possesses a locking taper that creates a bacterial seal at the IAI and prevents bacterial access to the inner spaces of the implant.[15,44] As a result of the bacterial seal that is formed at their IAI, Bicon implants have the potential to reduce the accumulation of deleterious bacteria in and around the implant, thereby causing a reduction in the incidence of implant-related pathologies among implant recipients. In addition to the evidence reviewed here, clinical observations reported by clinicians over the past three decades support the existence of a bacterial seal at the Bicon IAI. Unpleasant odor—a strong indicator of bacterial contamination—is regularly reported as being absent upon removal of Bicon abutments. Moreover, bone regeneration and the absence of soft tissue inflammation coronal to the IAI are both highly unlikely in a septic environment.

Because of the Bicon system’s advantageous design and its accommodation of single-crown restorations, Bicon implants are well suited to provide conditions that not only permit a favorable response to the treatment of periimplant and bone diseases but also allow for adequate home-care procedures such as effective brushing and interdental flossing—patient habits that can halt the development and progression of peri-implant disease. In addition to the treatments presented in this chapter, there are

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23. Aloise JP, Curcio R, Laporta MZ, Rossi L, da Silva AMA, Rapoport A. Microbial leakage through the implant-abutment interface of Morse taper implants in vitro. Clin Oral Implants Res 2010;21:328–335.

24. Faria R, Gressler May L, de Vasconcellos DK, Volpato CAM, Bottino MA. Evaluation of the bacterial leakage along the implant-abutment interface. J Dent Implants 2011;1:51–57.

25. Teixeira W, Ribeiro RF, Sato S, Pedrazzi V. Microleakage into and from two-stage implants: An in vitro comparative study. Int J Oral Maxillofac Implants 2011;26:56–62.

26. Alves DCC, Carvalho PS, Martinez EF. In vitro microbiological analysis of bacterial seal at the implant-abutment interface using two Morse taper implant models. Braz Dent J 2014;25:48–53.

27. Assenza B, Tripodi D, Scarano A, et al. Bacterial leakage in implants with different implant-abutment connections: An in vitro study. J Periodontol 2012;83:491–497.

28. D’Ercole S, Scarano A, Perrotti V, et al. Implants with internal hexagon and conical implant-abutment connections: An in vitro study of the bacterial contamination. J Oral Implantol 2014;40:30–36.

29. Tripodi D, Vantaggiato G, Scarano A, et al. An in vitro investigation concerning the bacterial leakage at implants with internal hexagon and Morse taper implant-abutment connections. Implant Dent 2012;21:335–339.

30. Jansen VK, Conrads G, Richter EJ. Microbial leakage and marginal fit of the implant-abutment interface. Int J Oral Maxillofac Implants 1997;12: 527–540.

31. Besimo CE, Guindy JS, Lewetag D, Meyer J. Prevention of bacterial leakage into and from prefabricated screw-retained crowns on implants in vitro. Int J Oral Maxillofac Implants 1999;14:654–660.

32. Guindy JS, Besimo CE, Besimo R, Schiel H, Meyer J. Bacterial leakage into and from prefabricated screw-retained implant-borne crowns in vitro. J Oral Rehabil 1998;25:403–408.

33. Schmitt CM, Nogueira-Filho G, Tenenbaum HC, et al. Performance of conical abutment (Morse Taper) connection implants: A systematic review. J Biomed Mater Res A 2014;102:552–574.

34. Al-Jadaa A, Attin T, Peltomäki T, Schmidlin PR. Comparison of three in vitro implant leakage testing methods. Clin Oral Implants Res 2013;26:e1–e7.

35. Mawhinney J, Connolly E, Claffey N, Moran G, Polyzois I. An in vivo comparison of internal bacterial colonization in two dental implant systems: Identification of a pathogenic reservoir. Acta Odontol Scand 2014;73: 188–194.

36. Tesmer M, Wallet S, Koutouzis T, Lundgren T. Bacterial colonization of the dental implant fixture-abutment interface: An in vitro study. J Periodontol 2009;80:1991–1997.

37. Merz BR, Hunenbart S, Belser UC. Mechanics of the implant-abutment connection: An 8-degree taper compared to a butt joint connection. Int J Oral Maxillofac Implants 2000;15:519–526.

38. Oberg EW, Jones FD. Machinery’s Handbook: A Reference Book for the Mechanical Engineer, Draftsman, Toolmaker and Machinist, ed 19. New York: Industrial Press, 1975.

39. Bozkaya D, Müftü S. Mechanics of the tapered interference fit in dental implants. J Biomech 2003;36:1649–1658.

40. Coelho PG, Sudack P, Suzuki M, Kurtz KS, Romanos GE, Silva NRFA. In vitro evaluation of the implant abutment connection sealing capability of different implant systems. J Oral Rehabil 2008;35:917–924.

41. Al-Jadaa A, Attin T, Peltomäki T, Heumann C, Schmidlin PR. Impact of dynamic loading on the implant-abutment interface using a gas-enhanced permeation test in vitro. Open Dent J 2015;9:112–119.

42. Guimarães MP, Nishioka RS, Bottino MA. Analysis of implant/abutment marginal fitting. Braz Dent Sci 2001;4(2):12–19.

43. Quirynen M, van Steenberghe D. Bacterial colonization of the internal part of two-stage implants. An in vivo study. Clin Oral Implants Res 1993;4: 158–161.

44. Meleo D, Baggi L, Di Girolamo M, Di Carlo F, Pecci R, Bedini R. Fixture-abutment connection surface and micro-gap measurements by 3D micro-tomographic technique analysis. Ann Ist Super Sanita 2012;48:53–58.

45. King GN, Hermann JS, Schoolfield JD, Buser D, Cochran DL. Influence of the size of the microgap on crestal bone levels in non-submerged dental implants: A radiographic study in the canine mandible. J Periodontol 2002;73:1111–1117.

46. Grande NM, Plotino G, Gambarini G, et al. Present and future in the use of micro-CT scanner 3D analysis for the study of dental and root canal morphology. Ann Ist Super Sanita 2012;48(1):26–34.

47. Di Carlo F, Marincola M, Quaranta A, Bedini R, Pecci R. Analisi MicroTac di impianti a connessione conometrica. Dent Cadmos 2008:76;55–60.

48. Jepsen S, Berglundh T, Genco R, et al. Primary prevention of peri-implantitis: managing peri-implant mucositis. J Clin Periodontol 2015;42(suppl 16):S152–S157.

49. Monje A, Aranda L, Diaz KT, et al. Impact of maintenance therapy for the prevention of peri-implant diseases: A systematic review and meta-analysis. J Dent Res 2016;95:372–379.

50. Albrektsson T, Dahlin C, Jemt T, Sennerby L, Turri A, Wennerberg A. Is marginal bone loss around oral implants the result of a provoked foreign body reaction? Clin Implant Dent Relat Res 2014;16:155–165.

51. Mombelli A, Buser D, Lang NP. Colonization of osseointegrated titanium implants in edentulous patients. Early results. Oral Microbiol Immunol 1988;3:113–120.

52. Becker W, Becker BE, Newman MG, Nyman S. Clinical and microbiologic findings that may contribute to dental implant failure. Int J Oral Maxillofac Implants 1990;5:31–38.

53. Alcoforado GA, Rams TE, Feik D, Slots J. Microbial aspects of failing osseointegrated dental implants in humans. J Parodontol 1991;10:11–18.

54. Jervøe-Storm PM, Jepsen S, Jöhren P, Mericske-Stern R, Enkling N. Internal bacterial colonization of implants: Association with peri-implant bone loss. Clin Oral Implants Res 2015;26:957–963.

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56. Mombelli A, Müller N, Cionca N. The epidemiology of peri-implantitis. Clin Oral Implants Res 2012;23(suppl 6):67–76.

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58. Roos-Jansåker A-M, Lindahl C, Renvert H, Renvert S. Nine- to fourteen-year follow-up of implant treatment. Part II: Presence of peri-implant lesions. J Clin Periodontol 2006;33:290–295.

59. Fransson C, Lekholm U, Jemt T, Berglundh T. Prevalence of subjects with progressive bone loss at implants. Clin Oral Implants Res 2005;16:440–446.

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07

The Survival of Short Implants

Somkid Tantirungkij | Joseph Leary

The performance of an implant system, taken in conjunction with factors such as patient satisfaction and user-friendliness, can be inferred by examining data concerning its longitudinal failure or success (ie, survival rates).[1] However, determining the failure, success, or survival rates of a given implant system can prove challenging when examining the literature: differences in variables such as research materials and methods and even differences in the definitions of the terms themselves (ie, failure, success, and survival) can result in ambiguity.

Overall Survival Rate

The criterion most frequently used to illustrate an implant system’s performance is survival. Survival of an implant system can be determined in terms of its continued endurance (ie, survival in its conventional sense: the implant continues to physically reside in the mouth) and in terms of failure (ie, the implant is removed from the mouth).[1]

Through years of trial and error, the use of osseointegrated implants to restore missing teeth has become a highly predictable and effective treatment.[2] In fact, dental implants are so effective and predictable, it is now rare to find an implant system with a reported survival rate of less than 74% to 100%.[3] As with most modern-day implant manufacturers, Bicon’s short implants have an outstanding overall survival rate.

The survival rates for Bicon dental implants (as reported in the literature) are summarized in Table 7-1.[3–10] Material modifications and the implementation of improved procedures gleaned from the lessons learned in each successive study contribute to the maintenance and improvement of the overall survival rates. For example, Erakat et al[11] reported that implants immediately placed and splinted to adjacent struc-

Summary of reported overall survival rates for Bicon Table 7-1 dental implants from ≤ 6.0 to 10.0 mm in length* *All implants placed 2.0 mm below the margin of the alveolar crest using a two-stage surgical procedure. †2.5 years. ‡5.8 years. §Mix of short and ultrashort implant sizes. ||3.5 years. NR, not reported.

tures had a survival rate of only 90.3%. From this study, it was learned that immediate placement after extraction, splinting to multiple pontics, and using uncoated implants led to higher failure rates.[11]

Five-Year Clinical Experience of a Novice Bicon Clinician

As shown in Table 7-1, the survival rates of Bicon’s short implants are comparable to the reported survival rates of implants in general.[12–16] Reviewing the survival rates reported in industry-sponsored research might elicit a healthy dose of skepticism; undoubtedly, such clinical trials are performed under ideal conditions and with the most competent clinicians to maximize success.[17,18] But what kind of real-world survival rates can the average clinician expect when using the Bicon implant system as a novice? To answer this question, the authors examined the performance of an experienced clinician who was a first-time user of the Bicon implant system. In addition to performing the diagnosis and placing the implants, this self-taught, first-time user was also able to personally fabricate the prostheses, all without prior training, and by using the information available from Bicon’s website (www.Bicon.com) as his only aid.

Over time, the first-time Bicon clinician placed 407 implants in 182 patients. The implants were of varying diameters, with lengths ranging from 6 to 8 mm. The patient population consisted of a mix of men and women, smokers and nonsmokers, with an average age of 56 years. Patients were observed for a period of 5 years. Of the 407 implants, only 8 implants failed, representing a 98% survival rate. Five representative treatments performed by the novice user of the Bicon system are presented below.

Treatment 1: Mandibular first molar

A 64-year-old man was referred for replacement of a missing mandibular left first molar (Fig 7-1a). Clinical examination revealed an atrophic alveolar ridge in both the buccolingual and occlusogingival dimensions. After a thorough medical history was taken, the following plan of treatment was established: The missing molar would be replaced using an Integra-CP 5.0 × 6.0–mm implant with an Integrated Abutment Crown (IAC) serving as the definitive restoration, and the extruded opposing maxillary molar would be restored to proper form (Figs 7-1b and 7-1c). A two-stage implant placement was performed. Following an uneventful healing period, the IAC was placed and checked for occlusion (Figs 7-1d and 7-1e). After 5 years of loading, the patient reported satisfaction, the implant was in function, and the adjacent hard and soft tissues were healthy (Figs 7-1f and 7-1g).

Treatment 2: Maxillary first and second molars

A 55-year-old woman was referred for treatment of missing maxillary left first and second molars (Fig 7-2a). During the initial examination, radiographs revealed minimal crestal bone (Fig 7-2b). Integra-CP 5.0 × 6.0–mm and 4.5 × 6.0– mm implants were chosen to replace the first and second molars, respectively (Figs 7-2c and 7-2d). Four months after the implant placement, two IACs were placed (Figs 7-2e to 7-2g). The implants and the IACs remained functional 5 years after placement, and the surrounding hard and soft tissues appeared healthy (Figs 7-2h and 7-2i). Fig 7-1 (a) Missing mandibular first molar and extruded maxillary molar. (b) Model with wax-up. (c) IAC prior to placement. (d and e) Clinical view and radiograph following placement of the IAC. (f and g) Clinical appearance and radiograph at 5-year follow-up. Fig 7-2 Preoperative site clinical appearance (a) and presurgical radiograph with 5.0-mm metal ball (b) . The metal ball was used as a guide to estimate bone height. (c) Postinsertion view of two short implants with black Healing Plugs. (d) Appearance of the surgical site after closure. (e to g) Lateral view, palatal view, and radiograph of the two IACs after placement. (h and i) Clinical appearance and radiograph after 5 years. Fig 7-3 (a and b) Preoperative clinical and radiographic views. (c and d) Appearance of the surgical site postextraction and with provisional acrylic teeth in place. (e and f) Appearance of the sockets 2 weeks and 3 months postextraction. (g) The 3-month postextraction radiograph shows healed sockets. (h) An incision is made at the location of the sockets. (i) Tissue healing 1 week after implant placement. (j) Ceramage (Shofu) is used to match the definitive restoration with the provisional acrylic tooth. (k) Initial try-in of the IACs. (l) The definitive restorations after custom buildup. —_>

Treatment 3: Maxillary central incisors

A 51-year-old woman was referred for replacement of her maxillary central incisors. Examination revealed failed endodontic treatment and compromised aesthetics (Figs 7-3a and 7-3b). The teeth were carefully extracted, and all granulation tissue was removed from the sockets, which were then packed with SynthoGraft in an effort to preserve the maximum height and width of the bone. A free pedicle graft harvested from the palate was used to achieve complete closure of the incision (Fig 7-3c). A removable partial denture was provided for aesthetics during the healing period (Fig 7-3d). After a period of 3 months, when the sockets had sufficiently healed, two 5.0 × 8.0–mm Integra-CP implants were placed (Figs 7-3e to 7-3i).

After 4 more months of healing, a polyceramic composite resin custom shade tab was used to ensure uniform color and shading of the definitive restorations (Fig 7-3j). The IACs were tried in and rebuilt to proper contour and crown length, and a radiograph was taken (Figs 7-3k to 7-3o). At the 5-year postoperative visit, the gingival tissues appeared healthy and the levels of crestal bone were consistent with the levels seen at the time of placement; furthermore, a substantial osseous defect on the mesial side of maxillary right central incisor had regenerated (Figs 7-3p and 7-3q). It is also noted that in Fig 7-3q the left central incisor appears extruded; a comparison of Figs 7-3l and 7-3q reveals that, when you consider the relationship between the right lateral and central incisors in Fig 7-3l, the apparent extrusion in Fig 7-3q is an artifact created by the camera angle. Fig 7-3 (cont) (m to o) Lateral, smile, and radiographic views after placement of the definitive IACs. (p and q) Radiographic and clinical appearance after 5 years.

Treatment 4: Maxillary right lateral incisor

A 50-year-old woman presented with a loose crown on her maxillary right lateral incisor (Fig 7-4a); the tooth had been endodontically treated 10 years previously (Fig 7-4b). The clinical examination revealed a loose, porcelain-fused-to-gold crown with a post and core still intact in the crown. When the post and crown were removed, there was a visible crack in the root running in the labiopalatal direction. No periodontal pockets were detected. The patient said that she was quite pleased with the natural appearance of the previous crown and desired that the new crown possess similar aesthetics. The proposed treatment involved the extraction of the remaining root followed by immediate placement of a Integra-CP 4.0 × 8.0–mm implant with a fixed acrylic tooth to serve as a provisional restoration during the healing phase.

To preserve the remaining thin alveolar bone, an atraumatic extraction was carried out with care using a periotome. The extraction socket was thoroughly curetted to remove any remnant of periodontal ligament and apical granulation tissue; this was followed by irrigation with a sterile normal saline solution. An Integra-CP 4.0 × 8.0–mm implant was placed and securely seated in the osteotomy. Bone harvested during the osteotomy preparation was placed over the sloping shoulder of the seated implant, which was then covered by a resorbable collagen plug and sutured closed (Fig 7-4c). The provisional acrylic tooth was secured to the adjacent teeth using a bonded fiber ribbon and composite resin material (Fig 7-4d). After 2 weeks, the gingival tissues appeared healthy, and the sutures were removed (Fig 7-4e).

Radiographic and clinical images taken at the time of the uncovering revealed excellent bone levels and healthy gingival tissues around the provisional crown and the Healing Abutment (Figs 7-4f and 7-4g). The Healing Abutment was reinserted into the implant well, and the provisional acrylic crown was rebonded to the adjacent teeth (Figs 7-4h to 7-4j). Two weeks after uncovering, a porcelain-fused-togold crown was cemented extraorally to the abutment (Fig 7-4k). The restoration was then inserted into the implant (Figs 7-4l and 7-4m). Follow-up clinical images and radiographs at 1 year show that the implant remains in function and is aesthetically pleasing (Figs 7-4n and 7-4o).

The Bicon dental implant is designed to be placed 2 to 4 mm below the alveolar crest. The subcrestal placement of the implant ensures a natural emergence profile, preventing the appearance of a dark metallic gingival margin. This patient was very apprehensive about the long-term aesthetic outcome; Bicon’s subcrestal design played a major role in achieving the excellent aesthetic result presented here. Furthermore, because the crown was cemented extraorally, extraneous cement could be easily removed. This prevented excess cement from being introduced deep into gingival tissue, which would ultimately cause deep sulcus gingival inflammation and possible bone loss. Fig 7-4 (a) Preoperative clinical appearance of the loose crown on the maxillary right incisor. (b) The preoperative radiograph shows endodontic treatment. (c) Postoperative radiograph. (d) The provisional acrylic tooth. (e) Clinical appearance of the provisional restoration in place after the sutures were removed. (f) Radiograph taken subsequent to implant uncovering. (g) Clinical appearance of gingival tissues after removal of the provisional abutment. (h) The Healing Abutment was inserted into the uncovered implant. (i and j) Facial and palatal views of the provisional acrylic crown after uncovering. (k) A porcelain-fused-to-gold crown was cemented extraorally to a prepared 4.0 × 6.5–mm, 15-degree, Non-Shouldered Abutment with a 2.5-mm well. (l and m) Clinical and radiographic appearance immediately after placement of the definitive porcelain-fused-to-metal crown. (n and o) Clinical and radiographic appearance at 1-year follow-up. Fig 7-5 (a and b) Preoperative clinical and radiographic appearance. (c) After placement of the implant, the socket was packed with surgical gauze. (d and e) Postsurgical appearance of the provisional acrylic tooth bonded to the adjacent teeth. (f and g) Clinical and radiographic appearance after seating the definitive prosthesis. (h and i) Appearance at 6-month recall.

Treatment 5: Mandibular right incisor

A 60-year-old woman was referred for treatment of a stained mandibular right central incisor with a buccolingual fracture line (Figs 7-5a and 7-5b). During the examination, the patient was diagnosed with acute apical periodontitis secondary to a vertical root fracture. The treatment plan called for extraction of the damaged tooth, followed by immediate placement of a Bicon implant. The provisional restoration would consist of an acrylic denture tooth bonded to the adjacent teeth with orthodontic wire and with composite on the lingual surfaces.

After the tooth was extracted, a 3.5 × 8.0–mm Bicon implant was placed (Fig 7-5c). The site was then sutured closed, and a provisional acrylic denture tooth was secured to adjacent teeth with composite (Figs 7-5d and 7-5e). Six months after implant placement, the definitive prosthesis was placed (Figs 7-5f and 7-5g). At the 6-month recall, the bone and gingival tissues remained healthy (Figs 7-5h and 7-5i).

Radiographic Studies 15 Years and Longer

There are numerous treatments demonstrating the survival of Bicon short implants for periods longer than 15 years. For the sake of brevity, the following examples only feature early and long-term follow-up radiographs to illustrate the long-term survival of this system.

Figure 7-6a shows a postsurgical radiograph after a customized 6.0-mm-long Bicon implant was placed simultaneous to a sinus elevation procedure in the location of implants had not been invented, but given the flexibility of this system, the operator was able to modify an 8.0-mmlong implant into a custom-made 6.0-mm-long implant. Fig 7-6 Radiographs of a 6-mm and two 11-mm-long implants: immediately following placement (a) , at 2-year follow-up (b) , and at 15-year follow-up (c) . the maxillary left first molar (adjacent 11-mm implants were also placed). Figures 7-6b and 7-6c show the 2-year and 15-year follow-up radiographs, respectively. At the 15-year follow-up, the soft tissues were reported to appear healthy, and the implant was clinically functional.

An additional example of short implant placement in the location of the maxillary left first molar is shown in Fig 7-7. The area of the intended implant placement was characterized by atrophic bone with the sinus floor in close proximity. A 6.0-mm-long implant was placed in the site following a sinus elevation procedure. As in the previous example, the implant remained in function and appeared to be well integrated after 15 years.

An example of implants placed in the proximity of the mandibular nerve can be seen in Fig 7-8. At the time, short

The radiograph in Fig 7-9a was taken at the time of restoration and shows two adjacent implants placed in the location of the right mandibular molars. Owing to the patient’s severely atrophic mandible, the placement of unmodified implants was not an option—short implants had yet to be invented. To avoid injury to the inferior alveolar nerve, the operator was able to adapt two 8.0-mm implants by shortening them to 7.0 mm prior to placement, which was completed successfully without an impact on the nerve. The implants have remained successfully in function for 17 years (Fig 7-9b).

Another example providing an elegant side-by-side comparison of the long-term success of both long and short implants is shown in Fig 7-10. A radiograph taken after placement of the definitive restoration shows one of the early 6.0 × 5.7–mm implants adjacent to an 11.0-mm-long implant; both the long and short implants are well osseointegrated. A radiograph taken at the 17-year follow-up examination shows that an additional 13-mm-long implant had been placed; more importantly, all of the implants continue to be functional and stable.

Figure 7-11a depicts a 5-year postplacement radiograph of a 6.0-mm-long implant placed in the posterior maxilla; Fig 7-11b shows the 18-year follow-up radiograph. As recently as 5 to 10 years ago, conventional wisdom claimed that such a short implant would be unable to support a molar restoration; nevertheless, the 18-year follow-up radiograph shown in Fig 7-11 contradicts this assertion.

Finally, yet another striking side-by-side comparison between long and short implants is shown in Fig 7-12. Because of the presence of severely atrophic bone, the clinician had to shorten an 8.0-mm-long implant by 2.0 mm. Despite this ad-hoc modification, the customized 6.0-mm implant and adjacent 11.0-mm-long implants have remained in function for over 20 years in a region of augmented bone. Fig 7-8 Radiographs of a 6.0-mm short implant placed in the mandible. This implant was modified chairside from an 8.0-mm implant to permit placement near the nerve. Radiograph at 4-year follow-up (a) and 15-year follow-up (b) . Fig 7-9 Postloading radiograph (a) and 17-year follow-up radiograph (b) showing two 8.0-mm implants that were shortened chairside to 7.0 mm. Placing unmodified implants was not an option because of the proximity of the alveolar nerve. Fig 7-10 (a) Postplacement radiograph showing an 11-mm-long implant adjacent to a 6.0 × 5.7–mm implant. (b) Follow-up radiograph at 17 years showing the 6.0 × 5.7–mm implant sandwiched between 11.0-mm and 13.0-mm-long implants. a b i Hav) Fig 7-12 Radiographs showing a 6.0-mm-long implant next to an 11.0-mmlong implant in a region of augmented bone after placement (a) and at 20-year follow-up (b) .

Conclusion

The survival rate is a starting point for clinicians when choosing an implant system. When used as a measure of performance, survival rates can inform as to how successful an implant system is. This chapter has shown that the short-term survival rates (ie, 1 to 5 years) of Bicon short implants are comparable to other longer, so-called conventional implants. Additionally, the performance of a clinician inexperienced in the use of the Bicon implant system has been demonstrated through clinical and radiographic images; these images show that in the context of the normal clinical setting, a newcomer to Bicon implants can achieve superior aesthetics and survival rates without splinting, even in the least favorable conditions of the posterior maxillary arch. The long-term treatments spanning over three decades demonstrate the hardiness, flexibility, and survivability of Bicon implants; these treatments illustrate that short implants are not only the answer to many challenging situations, but remain a reliable and predictable solution over time.

References

1. Misch CE, Perel ML, Wang HL, et al. Implant success, survival, and failure: The International Congress of Oral Implantologists (ICOI) Pisa Consensus Conference. Implant Dent 2008;17:5–15.

2. Tonetti MS. Determination of the success and failure of root-form osseointegrated dental implants. Adv Dent Res 1999;13:173–180.

3. Vehemente VA, Chuang SK, Daher S, Müftü A, Dodson TB. Risk factors affecting dental implant survival. J Oral Implantol 2002;28:74–81.

4. Urdaneta RA, Daher S, Leary J, Emanuel KM, Chuang SK. The survival of ultrashort locking-taper implants. Int J Oral Maxillofac Implants 2012;27:644–654.

   6. Gentile MA, Chuang SK, Dodson TB. Survival estimates and risk factors for failure with 6 × 5.7-mm implants. Int J Oral Maxillofac Implants 2005;20:930–937.

   7. Schulte J, Flores AM, Weed M. Crown-to-implant ratios of single tooth implant-supported restorations. J Prosthet Dent 2007;98:1–5.

   8. Al-Hashedi AA, Taiyeb-Ali TB, Yunus N. Outcomes of placing short implants in posterior mandible: A preliminary randomised controlled trial. Aust Dent J 2016;61:208–218.

   9. Urdaneta RA, Seemann R, Dragan IF, Lubelski W, Leary J, Chuang SK. A retrospective radiographic study on the effect of natural tooth-implant proximity and an introduction to the concept of a bone-loading platform switch. Int J Oral Maxillofac Implants 2014;29:1412–1424.

   10. Morgan KM, Chapman RJ. Retrospective analysis of an implant system. Compend Contin Educ Dent 1999;20:609–614.

   11. Erakat MS, Chuang SK, Yoo RH, Weed M, Dodson TB. Immediate loading of splinted locking-taper implants: 1-year survival estimates and risk factors for failure. Int J Oral Maxillofac Implants 2008;23:105–110.

   12. Thoma DS, Haas R, Tutak M, Garcia A, Pietro Schincaglia G, Hämmerle CH. Randomized controlled multicentre study comparing short dental implants (6 mm) versus longer dental implants (11–15 mm) in combination with sinus floor elevation procedures. Part 1: Demographics and patient-reported outcomes at 1 year of loading. J Clin Periodontol 2015;42:72–80.

   13. Omran MT, Miley DD, McLeod DE, Garcia MN. Retrospective assessment of survival rate for short endosseous dental implants. Implant Dent 2015;24:185–191.

   14. Moraschini V, Poubel LA, Ferreira VF, Barboza ED. Evaluation of survival and success rates of dental implants reported in longitudinal studies with a follow-up period of at least 10 years: A systematic review. Int J Oral Maxillofac Surg 2015;44:377–388.

   15. Esposito M, Hirsch JM, Lekholm U, Thomsen P. Failure patterns of four osseointegrated oral implant systems. J Mater Sci Mater Med 1997;8:843–847.

   16. Nisand D, Picard N, Rocchietta I. Short implants compared to implants in vertically augmented bone: A systematic review. Clin Oral Implants Res 2015;26(suppl 11):170–179.

   17. Popelut A, Valet F, Fromentin O, Thomas A, Bouchard P. Relationship between sponsorship and failure rate of dental implants: A systematic approach. PLoS One 2010;5:e10274.

   18. Faggion CM, Atieh M, Zanicotti DG. Reporting of sources of funding in systematic reviews in periodontology and implant dentistry. Br Dent J 2014;216:109–112.

5. Venuleo C, Chuang SK, Weed M, Dibart S. Long term bone level stability on short implants: A radiographic follow up study. J Maxillofac Oral Surg 2008;7:340–345.

08

Treatment Planning and Basic Procedures

Muneki Hirayama | Drauseo Speratti | Laura Murcko

The Bicon dental implant is unique not only in its design but also in its surgical protocols. Since its inception in 1985, Bicon has advocated a surgical implant placement technique wherein the osteotomy is prepared either with Hand Reamers or by drilling slowly with Latch Reamers at 50 rpm without irrigation. The use of these techniques generates minimal heat—if any—which in turn preserves bone physiology as well as predictability. Slow drilling and Hand Reamers also provide greater control and flexibility during the preparation of an osteotomy.

The slow rotation of the drill expands the operator’s comfort zone, enabling a more deliberate approach to vital anatomical structures such as the incisive canal and inferior alveolar nerve. The Hand Reamer’s unique design also provides the level of control required to meet even the most challenging placement situations. When viewed from an economic perspective, Bicon reamers are more cost-effective in that they can be used to prepare over 200 osteotomies before requiring replacement, a significantly greater number of osteotomies than is allowed by internally irrigated burs. Following use, these simple and durable reamers can be both cleaned and sterilized, whereas the internal bores of burs can be sterilized but not cleaned.

Eliminating irrigation during the procedure provides the following benefits: It increases the clinician’s visibility; reduces the need for suctioning, which frees an assistant’s hands and is more comfortable for the patient; and most importantly, prevents bone and blood from being washed away from the surgical site. Fig 8-2 Flutes of bone in a 3.0- or 3.5-mm Hand Reamer: (a) type I, (b) type II, (c) type III, and (d) type IV.

Treatment Planning

Implant size

Implant selection should be based on the location and characteristics of the intended implant site. The location of the intended implant site dictates the functional role that the implant will play and how the surrounding structures will affect its function. The characteristics of the intended implant site include the volume and type of bone (ie, bone type I to IV) and the presence of adjacent structures and anatomy (eg, other implants, inferior alveolar nerve, and sinus floor).

Figure 8-1 provides a series of implant recommendations based on location. Many maxillary anterior implants are placed in less-than-ideal situations, where the forces of occlusion can adversely affect the retention of single unsplinted abutments; therefore, an implant with a well diameter of 2.5 mm should always be used because it is designed to resist loosening from the rotary forces of occlusion.

Because 5.0- and 6.0-mm short implants are capable of supporting prostheses in all areas of the mouth, clinicians should focus on choosing the diameter of an implant that provides for a minimum of 1.0 mm of bone around the implant. Certain extraction sites may require the use of the 8.0-mm implants to achieve stability. Always try to have thick bone covering the facial of the implant.

Bone quality

Bone quality is arbitrarily described as type I, II, III, or IV during the reaming stage of the surgical procedure. The quality is assessed by visibly inspecting the appearance and consistency of bone that accumulates in the flutes of the reamer during this stage. The bone is then designated by type, and this classification is used to estimate the time required for the implant to become osseointegrated.

Bone classified as type I comprises dense cortical bone. When type I bone is examined in the flutes of a reamer, it appears as a solid white cylinder with a minimal amount of blood (Fig 8-2a). It requires approximately 16 weeks to osseointegrate with the implant. Bone classified as type II comprises a mixture of porous cortical bone and coarse trabecular bone (Fig 8-2b). When examined on a 3.0-mm reamer flute, the bone appears as a semisolid cylinder of bone interspersed and fully wetted with blood, and it requires approximately 10 to 12 weeks to osseointegrate. Type III bone comprises porous cortical and fine trabecular bone (Fig 8-2c). It is similar to type II bone (albeit with more blood), and requires approximately 12 weeks to osseointegrate. The distinction between types II and III is somewhat arbitrary in that the two types are similar and require nearly the same amount of time to osseointegrate. Finally, type IV bone comprises fine trabecular bone and requires 16 to 20 weeks to osseointegrate, often with ancillary procedures that use a bone-grafting substitute

Minimum recommended armamentarium for Bicon Box 8-1 implant placement

• Shoulder Depth Gauge

• Removal Wrench

  • Paralleling Pins

  • Osteotomes

• Double-Ended Osteotomy • Implant/Abutment Seating Tips Depth Gauge • Threaded Instrument Adapter

• Threaded Straight Handle • Hand Reamers

• Implant Inserter/Retriever

• Threaded Offset Handle

  • Guide Pins

  • Sulcus Formers

• Latch Reamers • Threaded Knob

• Pilot Drills

• Healing Plug Removal Instrument

Fig 8-3 (a) The ideal placement of a Bicon implant is 2 to 3 mm below the alveolar bone crest. (b) Radiograph showing the subcrestal placement of an implant in close proximity to adjacent teeth.

for bone such as SynthoGraft, a pure-phase beta-tricalcium phosphate. Examining a reamer of type IV bone reveals only blood with no visible bone (Fig 8-2d).

Insertion depth

Because Bicon’s locking-taper implant-abutment connection is bacterially sealed and exhibits no micromovement, the implant may be placed subcrestally without causing bone loss. This feature of placement provides the opportunity to place implants in adolescents whose alveolar ridges are not fully formed (see chapter 10). Although the implant may be placed at or even above the crest of bone, it is ideally placed 2 to 3 mm below the crest.

The subcrestal placement of an implant with a sloping shoulder design not only provides the opportunity to initiate the restoration’s emergence profile subgingivally, but also creates the environment for the sloping shoulder to transfer occlusal forces to the surrounding bone. Additionally, this design feature provides sufficient space for the formation of bone-supported interdental papillae, which in turn produces the conditions for the development of aesthetic restorations (Fig 8-3). The sloping shoulder design also facilitates ridge-splitting techniques with implants being placed 2 to 3 mm below the crest of bone.

Overview of Surgical Procedures

Although this chapter deals primarily with surgical issues, we must also consider nonsurgical procedures such as the fabrication of surgical stents and abutment placements, given that they are closely tied to carrying out the surgery. There are four possible implant placement techniques with the Bicon system: two-stage, single-stage, immediately loaded, and guided surgery. Apart from some minor differences, the four techniques share many similarities and can be performed immediately following the extraction of a tooth and in healed extraction sites.

It is essential to have an appropriate armamentarium prior to beginning any surgery. A list of the minimum recommended instruments required to perform the placement of a Bicon implant can be found in Box 8-1. Additional instruments and devices required for guided surgery are listed in the guided surgery section.

Step-by-step quick-reference guides for the four surgical techniques can be found in Boxes 8-2 to 8-5 (see respective sections). After reviewing this chapter, use the quick guides as references prior to performing the actual procedures. It is also recommended that clinicians familiarize themselves with the bone-grafting techniques prior to preparing an osteotomy (see chapter 19).

Surgical templates

Because dental implantology is a restorative treatment with a surgical component, it is essential to be cognizant of the intended prosthetic restoration before performing the surgical procedure. Therefore, it is prudent to know the indented dental anatomy and to prepare a surgical guide. To achieve this, the intended dental anatomy can be designed via diagnostic wax-ups on mounted study casts, which can also be used to fabricate a surgical template and a provisional prosthesis. Although there are many techniques and types of surgical guides available, the simplest is often the best. In fact, the need for a template or a specific type can vary with the clinical situation.

A clinician can use the edentulous ridge and the adjacent teeth as a guide without any other devices by simply initiating the pilot osteotomy in the center of the edentulous space of the intended tooth with a trajectory parallel to the adjacent teeth.

Another straightforward approach is to use a surgical template made from a vacuum-formed template of a stone Fig 8-4 Use of a vacuum-formed surgical template as a guide.

Fig 8-5 (a) A line is drawn along the incisal edge and occlusal surface of a duplicate stone model. An intersecting line is drawn on the incisal edge and occlusal surface on the teeth that will be replaced (shown in green ). (b) The lingual halves of the teeth that will be replaced are removed from the stone model. (c) Acrylic is applied onto the lingual aspect of the model up to the level of the central fossa or incisal edge of the teeth to be restored. (d) Grooves 2.5-mm wide are cut into the acrylic at the intended implant location to accommodate the 2.0-mm pilot drill.

model or fabricated from an existing prosthesis. To make a vacuum-formed template, a thin template stock (which is commonly used for chairside fabrication of provisional restorations) is formed on a cast of a diagnostic wax-up. Then a hole is drilled in the middle of the incisal or occlusal surface of the template in the location of the intended tooth (Fig 8-4). If the dental situation permits, the vacuum-formed template should include at least one tooth distal and three or four teeth mesial to the intended implant location.

To make a surgical template from a stone model, a duplicated model is made from the diagnostic wax-up (Fig 8-5). A line is drawn along the incisal edge and occlusal surfaces of the teeth, and another line is drawn in the center of each tooth that will be replaced (see Fig 8-5a). The lingual halves of the teeth are then removed from the stone model (see Fig 8-5b). Acrylic is then applied onto the lingual aspect of the model up to the level of the central fossa or incisal edge of the teeth to be restored (see Fig 8-5c). To complete the template, 2.5-mmwide grooves are cut into the acrylic at the intended implant location (see Fig 8-5d).

For large edentulous areas, a palatal template can be fabricated based on an existing prosthesis (Fig 8-6). When fabricating the palatal template, the buccal aspect is inclined from the incisal edge or central fossa of the proposed teeth back to the crest of the alveolar ridge, which is represented on a duplicated prosthesis as the greatest concavity on the alveolar ridge side of the prosthesis. To fabricate the template, the existing denture is inserted into a denture duplicator containing alginate (see Fig 8-6a). A separating medium is applied, and the other side of the duplicator is filled with alginate; it is then closed and the alginate is allowed to set (see Fig 8-6b). After the alginate has been allowed to set, the denture is removed and replaced with acrylic, which also is allowed to set (see Figs 8-6c and 8-6d). After removing the duplicated acrylic denture (see Fig 8-6e), a line is drawn in the middle of each tooth, along with a line representing the greatest concavity on the tissue side (see Fig 8-6f). Next, 2.5-mm-wide grooves are made in the center of each tooth, joining the lines representing the middle of each tooth and greatest concavity of the tissue side (see Fig 8-6g). The buccal acrylic along the slope joining these two lines is then removed. Finally, any excess incisal length is trimmed off to prevent interference with the head of the handpiece (see Fig 8-6h). Alternatively, these practical surgical guides can be digitally designed and digitally printed in a far more expedient manner (Fig 8-7).

Contrary to what is presently being espoused, and although in some cases there may be a need for it, three-dimensional imaging should never be mandated as the standard of care prior to placing a dental implant.

Two-stage surgical procedure

Implant site preparation

There are many appropriate surgical flap designs for the placement of an implant (eg, envelope, scalloped). Whichever design is used, it should be a broad-based flap that Fig 8-6 (a) The existing denture is inserted into a denture duplicator containing alginate. (b) After a separating medium is applied to the denture, the other side of the denture duplicator is filled with alginate, the denture duplicator is closed, and the alginate is allowed to set. (c) The denture is removed from the hardened alginate. (d) The alginate mold is filled with acrylic, the denture duplicator is closed, and the acrylic in the alginate mold is allowed to set. (e) The duplicated acrylic denture template is removed. (f) A line is drawn in the middle of each tooth (left) and along the greatest concavity on the tissue side (right) . (g) A 2.0-mm-wide groove is made in the center of each tooth, joining the lines representing the middle of each tooth and greatest concavity of the tissue side. (h) The buccal acrylic along the slope joining these two lines is then removed, and the excess incisal length is trimmed off the template to prevent interference with the head of the handpiece.

Fig 8-7 A digitally printed surgical guide provides an expedient alternative to duplicating a denture.

Fig 8-8 A papillae-sparing flap design should be used for implant placement. Fig 8-9 (a) The initial depth of the pilot osteotomy should be approximately 6 mm. Here, the drilling depths for 5.0- and 6.0-mm-long implants are shown. The markings on the pilot drill can be used to assess current depth while drilling. (b) Create the initial osteotomy using a pilot drill at 1,100 rpm (irrigation is optional). (c) A pilot drill is used to create the initial osteotomy without irrigation. Fig 8-10 (a) A paralleling pin is used to confirm the intended osteotomy trajectory. (b) Radiograph confirming the trajectory of the osteotomy.

Fig 8-11 Illustration showing the confirmation of pilot osteotomy trajectory using a vacuum-formed template placed over an abutment with a 2-mm post inserted into the osteotomy.

preserves the papillae and attached tissue (Fig 8-8). After creating the flap and exposing the alveolar crest, prepare the osteotomy by advancing the pilot drill to a depth of 6.0 mm at a speed of 1,100 rpm with or without irrigation (Fig 8-9). Drilling a pilot bur without irrigation may sound unusual for long-term clinicians; however, the high-pressure irrigation flushes away the molecular factors responsible for positive bone-regeneration outcomes. Therefore, the use of irrigation is unnecessary at all stages of Bicon implant procedures.[1] Bicon has fully recognized the imperative to avoid overheating the bone and has designed the system to preclude that happening if the prescribed protocols are followed.

It is advisable to initially drill to a depth of only 6.0 mm, as this is the minimum depth where the appropriateness of the osteotomy can be determined (and also changed, if desired). Confirm the angle of the initial osteotomy by placing a paralleling pin or a straight abutment with a 2.0-mm shaft directly into the osteotomy (Fig 8-10). It is recommended that the trajectory of the pilot osteotomy be further confirmed by taking a radiograph of the inserted paralleling pin, especially when the proximity of adjacent teeth or anatomy is involved (eg, inferior alveolar canal). A surgical assistant may also view the trajectory of the pilot drill from the opposite side of the patient. A vacuum-formed template may also be used to confirm the trajectory of the osteotomy by placing it over the abutment (Fig 8-11). If the pilot osteotomy trajectory is found to be satisfactory, reinsert the pilot drill and drill to a final depth that is normally 2 to 3 mm deeper than the chosen implant length.

The initial pilot osteotomy is then gradually widened through the sequential use of 0.5-mm-wider Hand or Latch Reamers (Figs 8-12a and 8-12b). Hand Reamers, unlike Latch Reamers, possess a single vertical cutting edge that ends at the apex of the reamer. The single cutting edge of the Hand Reamers allows them to both deepen and widen an osteotomy. This design allows the operator to shape the osteotomy with deliberate, less than 360-degree, half-circle motions, as opposed to the Latch Reamer, which shapes uniform 360-degree circular motions. Fig 8-12 Latch Reamers (a) have a blunt tip and two cutting edges. Hand Reamers (b) have a sharp tip and only one cutting edge. Hand Reamers are usually attached to a threaded straight handle; however, they may be converted to rotary instruments by attaching them to a threaded instrument adapter. (c) The tip of a Hand Reamer has sharp edges that enable it to deepen an osteotomy, whereas the blunt tip of a Latch Reamer does not. (d) Illustration of a threaded instrument adapter.

Fig 8-13 During the reaming process, autogenous bone accumulating in the reamers should be harvested and placed in a dappen dish for future use. Fig 8-14 Illustration (a) and clinical photograph (b) showing a spoon excavator being used to harvest any loose bone or debris that remains in the osteotomy after widening it to the final implant diameter. It is essential that the osteotomy be cleared of any remaining bone.

Using the Hand Reamer, the operator is afforded the high level of control necessary when encountering challenging conditions such as thin facial bone or minimal bone between the osteotomy and adjacent teeth or implants. The operator will also find the Hand Reamer invaluable when working within the confines of a fresh maxillary anterior socket, in which the Hand Reamer can be used to enlarge the osteotomy by engaging only the palatal aspect of the socket while avoiding the fragile buccal wall. The Hand Reamer with its sharp tip can also be used for a controlled in-fracture of the sinus floor during a sinus floor elevation procedure (see chapter 12) (Fig 8-12c). When the need arises, the Hand Reamer can also deepen an osteotomy, whereas a Latch Reamer has a blunt end and cannot deepen an osteotomy. This is an important difference because attempting to deepen the osteotomy with a Latch Reamer could generate undesirable heat and compromise the bone’s ability to heal properly. The Hand Reamer is a very versatile instrument that may also be used as a rotary instrument by attaching it to a threaded instrument adapter (Fig 8-12d). Therefore, the choice to use Hand Reamers, Latch Reamers, or both should be a function of a clinician’s preference and a patient’s anatomy.

When using Latch Reamers, a two-handed technique should be used: one hand grasping the handpiece while the other hand holds the head of the handpiece between the thumb and forefinger to stabilize the handpiece, while applying apical pressure to the Latch Reamer.

During the reaming process, autogenous bone accumulating in the flutes of the reamers should be harvested and contained in a dappen dish for future use (Fig 8-13). The harvested bone should then be classified as type I, II, III, or IV to estimate the anticipated osseointegration time. Once the osteotomy has been widened to the intended implant diameter, it is essential to remove any bone chips, which may prevent the proper seating of the implant by harvesting them using a spoon-shaped curette; while doing this, the operator should also ensure that the integrity of the four walls and floor of the osteotomy have been maintained (Fig 8-14). For dense bone, the intended-diameter reamer should be used two or three times to facilitate the passive seating of the implant. Fig 8-15 (a) The implant/Healing Plug can be seated using an appropriate seating tip (left) or the implant can be seated without the Healing Plug (right) . (b) An implant/ Healing Plug about to be placed in an osteotomy. (c) Seating an implant and Healing Plug with an implant seating tip. (d) Seating an implant with an implant seating tip. (e) View of implant after being seated with an implant seating tip. Note the absence of the black Healing Plug. Fig 8-16 Appearance of an implant with the black Healing Plug cut.

Fig 8-17 (a) Autogenous bone collected during the reaming stage of the procedure is used to cover the implant and Healing Plug. (b) Appearance of the implant and osteotomy site after being covered with autogenous bone.

Prior to using the Latch Reamers, it may be advisable to countersink the orifice of the pilot osteotomy with a round bur or Sulcus Former, especially if the bone on one side of the osteotomy is higher or denser than on the other side. The higher or denser bone will tend to displace the reamers to the side of the lower or less dense bone. In addition to countersinking, hand pressure should be used to resist any inadvertent displacement. If a wall or floor of the osteotomy has been breached, additional grafting procedures or postponement of implant placement altogether may be necessary. A discussion of bone-grafting procedures can be found in chapter 19.

Implant placement

After removing the blister pack from its packaging, use a sterile technique to cut an opening in the pack with a pair of scissors. The implant/Healing Plug combination can be placed directly into the osteotomy, or the Healing Plug can be removed, and the implant can be placed into the osteotomy 2 or 3 mm below the crest of bone using an Implant Inserter/ Retriever instrument or the appropriate seating tip (Fig 8-15).

After the implant is seated, the black Healing Plug must be trimmed so that it is even with or slightly above the implant well. The trimming can be done with scissors or a blade while the plug is still in the implant well, or it can be cut with the plug removed from the implant well. However it is done, the goal is to cut the plug cleanly to ensure that there are no irregular or sharp edges that may irritate the mucosa and delay soft tissue healing. The most predictable approach is to remove the plug from the implant well and use a scalpel to create a clean, smooth edge. After trimming, replace the plug securely in the implant well (Fig 8-16).

Finally, cover the implant and osteotomy with the previously harvested bone and close the soft tissue flap (Fig 8-17). If a relaxed primary closure is not possible, the operator may use a leukocyte- and platelet-rich fibrin (LPRF) membrane or even a free pedicle graft from the palate. Conclude the placement phase of the procedure by covering and suturing the site.

Implant uncovering

After the designated healing period, the implant is preferably uncovered using a scalpel or laser. A Tissue Punch can also be used, but only if there is ample keratinized or attached tissue. To create an aesthetic uncovering, the aim is twofold: to gain access to the implant and to retain a band of attached gingiva on the facial aspect to allow for facial coverage of the emerging metal base of the abutment. Fig 8-18 A scalpel is used to make a Fig 8-19 After creating a flap and semilunar incision that exposes the imuncovering the implant, bone that has plant in the aesthetic area and creates grown over it is removed. a split-thickness flap.

Fig 8-20 The black Healing Plug is Fig 8-21 A guide pin is inserted into removed from the implant during the the implant well to check the integrauncovering phase. tion and angulation of the implant. Fig 8-22 (a) A sulcus reamer attached to a straight handle is placed over the guide pin and rotated to remove extraneous tissue. (b) Clinical photograph of a 5.0-mm sulcus reamer being used to remove extraneous tissue that may affect placement of the definitive abutment. (c) The appearance of an ideally formed sulcus. By using the sulcus reamer, any hard or soft tissues that would have a negative effect on the definitive abutment have been removed.

To achieve this, the initial incision should be semilunar in shape and oriented somewhat to the palatal or lingual side, and the small split-thickness flap should be gently elevated toward the facial side so the implant site can be seen (Fig 8-18). The black Healing Plug may be visible beneath the thin residual tissue, or bone may have grown over it. Any soft or hard tissue covering the implant is removed (Fig 8-19). The black Healing Plug is removed using the Healing Plug removal instrument or any other appropriate instrument, such as the tip of a curette, an endodontic file, round bur, or rongeur. The black Healing Plug is removed in a manner similar to removing a cork from a wine bottle (Fig 8-20).

Following the removal of the Healing Plug, a guide pin is inserted into the implant well; it is at this point that the integration and angulation of the implant can be evaluated (Fig 8-21). Apical movement of the implant usually indicates the need to replace the implant, whereas only slight lateral movement usually indicates the need for more time for integration. After evaluating the implant, a color-coded Sulcus Former of the same diameter as the intended implant is attached to a straight handle or knob and seated onto the guide pin. It is rotated with apical pressure to remove any

Fig 8-23 The well of implant is flushed with water.

hard or soft tissue that may affect the definitive seating of the abutment (Fig 8-22). After forming the sulcus, the implant well is flushed with water (Fig 8-23).

Abutment placement and provisional crown

At this point in the procedure, a white Scanning Post can be inserted into the well of the implant for the scanning and making of a digital impression. Alternatively, an implant- Fig 8-24 Impression Components: Impression Posts, Impression Sleeve, and Implant Analog. (a) 2.0-mm (Red). (b) 2.5-mm (Blue). (c) 3.0-mm (Green). (d to f) Assembled Impression Components. Fig 8-25 (a) An example of a polyetheretherketone (PEEK) transitional abutment. (b) An example of three titanium Temporary Abutments. (c) An example of two titanium definitive abutments. (d) The abutment is placed in the implant. Fig 8-26 A template may be used to confirm the appropriateness of the abutment prior to engaging the locking taper. The locking taper is engaged by tapping the abutment along its long axis.

level transfer impression may be made, which is done by first placing a color-coded metal impression post into the well of the implant and then placing its corresponding acrylic sleeve onto the post prior to applying a polyvinyl siloxane material around them (Fig 8-24). Subsequently, either a Transitional or Universal Abutment with the widest hemispheric base possible is inserted into the well of the implant (Fig 8-25). To engage the abutment’s locking taper, tap on the abutment along its long axis (Fig 8-26). To fabricate the provisional crown, place an Emergence Cuff or temporization sleeve onto the abutment and then inject a temporization material around the cuff or sleeve and into a vacuum-formed template. This is then placed over the abutment (Fig 8-27). Temporization material is then polished to become confluent with the Emergence Cuff or temporization sleeve to facilitate the formation of a soft tissue sulcus prior to the insertion of the definitive restoration.

Alternatively, without making an implant-level transfer impression, an appropriate definitive or provisional abutment with the widest hemispheric base practical can be placed into the implant to allow the soft tissue to heal prior to making an impression for the definitive restoration. Box 8-2 provides a step-by-step guide for this technique. Fig 8-27 (a) An Emergence Cuff or temporization sleeve is placed on the abutment to serve as the basis for the provisional restoration. (b) Acrylic is injected around the Emergence Cuff or temporization sleeve and into the vacuum-formed template. (c) The vacuum-formed template is placed on the abutment, where it serves as a provisional crown.

Box 8-2 Two-stage technique: Step-by-step guide

1. Expose the alveolar crest by creating a broad-based flap that preserves the 11. Trim the black Healing Plug, ensuring that no sharp edges remain, and papillae and attached tissue. place it in the implant well.

2. With the pilot drill, create an approximately 6.0-mm-deep osteotomy at 12. Cover the implant with the previously harvested autogenous bone from 1,100 rpm without irrigation. the dappen dish.

3. Confirm the trajectory of the pilot hole with a paralleling pin, or use a 13. Close the flap. vacuum-formed template placed over an abutment with a 2.0-mm post. 14. Allow osseointegration to occur for a time period indicated by bone type. (Taking a radiograph is recommended, even for experienced clinicians.) 15. To uncover the implant, take a scalpel and make a semilunar incision that

4. Continue using the pilot drill to advance the osteotomy to 2 to 3 mm exposes the implant in the aesthetic area and creates a split-thickness flap. deeper than the final implant length. 16. Remove any bone that has grown over the implant.

5. Use either Latch Reamers or Hand Reamers to widen the osteotomy. 17. Insert a guide pin into the implant well and check the integration and an• If using Hand Reamers, attach the 2.5-mm Hand Reamer to the rotary gulation of the implant. reamer and widen the osteotomy sequentially, at 0.5-mm increments, 18. Attach a Sulcus Former (with the same diameter as the desired abutment) to the diameter of the intended implant. to a straight handle.

• If using Latch Reamers, attach the 2.5-mm Latch Reamer to an electric 19. Guide the Sulcus Former onto the guide pin, and rotate it to remove any drill system and widen the osteotomy sequentially, at 0.5-mm incretissue that may impinge the definitive abutment. 20. Flush the well with water.

• If using Latch Reamers, attach the 2.5-mm Latch Reamer to an electric drill system and widen the osteotomy sequentially, at 0.5-mm increments, rotating at 50 rpm, to the diameter of the intended implant.

6. During the reaming process, intermittently harvest any autogenous bone 21. Insert the abutment into the implant well. that accumulates in the reamer and place it in a dappen dish. 22. Engage the locking taper by gently tapping.

7. Use a spoon excavator to harvest any remaining bone debris. 23. Place an Emergence Cuff or temporization sleeve onto the abutment. 8. Inspect the four walls and floor of the osteotomy to make sure they are 24. Inject acrylic around the Emergence Cuff or temporization sleeve. intact. 25. Inject acrylic into the vacuum-formed template.

8. Remove the implant/Healing Plug from its sterile blister pack using an 26. Place the vacuum-formed template on the abutment. aseptic technique. 27. Polish the acrylic so that it becomes confluent with the Emergence Cuff or

9. Insert the implant into the osteotomy and seat it using either an appropritemporization sleeve. ately sized seating tip or an Implant Inserter/Retriever instrument. 28. Wait for the soft tissues to heal prior to taking a final impression.

Box 8-3 Single-stage technique: Step-by-step guide

1. Expose the alveolar crest by creating a broad-based flap that preserves the papillae and attached tissue.

2. With the pilot drill, create an initial osteotomy that is 2 to 3 mm deeper than the final implant length, drilling at 1,100 rpm without irrigation.

3. Confirm the trajectory of the osteotomy by inserting an abutment with a 2.0-mm post.

4. Use either Latch Reamers or Hand Reamers to widen the osteotomy.

• If using Hand Reamers, attach the 2.5-mm Hand Reamer to the rotary reamer and widen the osteotomy sequentially, at 0.5-mm increments, to the diameter of the intended implant.

• If using Latch Reamers, attach the 2.5-mm Latch Reamer to an electric drill system and widen the osteotomy sequentially, at 0.5-mm increments, rotating at 50 rpm, to the diameter of the intended implant.

5. During the reaming process, intermittently harvest any autogenous bone that accumulates in the reamer and place it in a dappen dish.

6. Use a spoon excavator to harvest any remaining bone debris.

7. Inspect the four walls and floor of the osteotomy to make sure they are intact.

• If the intended Temporary Abutment is wider than the osteotomy, use a larger-diameter reamer to create a countersink.

8. Remove the implant/Healing Plug from its sterile blister pack using an aseptic technique.

9. Remove the black Healing Plug from the implant.

10. Insert a Temporary Abutment into the implant well.

11. Place the implant/abutment into the osteotomy.

• If necessary, trim any tissue that impinges on the Temporary Abutment.

• If space allows, cover the implant with the previously harvested autogenous bone from the dappen dish.

12. Allow osseointegration to occur for a time period indicated by bone type.

13. Remove the Temporary Abutment.

14. Flush the well with water.

15. Insert the abutment into the implant well.

16. Engage the locking taper by gently tapping it.

17. Place an Emergence Cuff or temporization sleeve onto the abutment.

18. Inject acrylic around the Emergence Cuff or temporization sleeve.

19. Inject acrylic into the vacuum-formed template.

20. Place the vacuum-formed template on the abutment.

21. Polish the acrylic so it becomes confluent with the Emergence Cuff or temporization sleeve.

22. Wait for the soft tissues to heal prior to taking a final impression.

Single-stage surgical procedure

The single-stage surgical procedure includes many of the same initial steps as the two-stage procedure; however, the single-stage procedure begins to deviate at the time of implant placement. Instead of placing a black Healing

Plug into the well of the implant, a transitional transmucosal abutment is placed, which eliminates the need for a second surgical procedure for the uncovering of the implant. A step-by-step quick guide for the single-stage surgical procedure is found in Box 8-3.

Fig 8-28 (a) Appearance of the extraction site immediately after extraction of the teeth. (b) A surgical guide may be used to assist in aiming the pilot drill toward the correct trajectory. b Fig 8-29 (a) A pilot drill operated at 1,100 rpm without irrigation is used to create the osteotomy. (b) Four paralleling pins are used to confirm the trajectory of the osteotomy. (c) A 4-mm Latch Reamer is used to widen the osteotomy. (d) A spoon excavator is used to harvest any loose bone or debris that remains in the osteotomy and to evaluate the integrity of the osteotomy walls. (e) An Implant Inserter/Retriever instrument is used to seat a 4.0 × 6.0–mm implant. (f) A straight-handled driver is used to seat a 4.0 × 6.0–mm implant. (g) Appearance of the four Universal Abutments after being tapped into place. (h) Trimmed acrylic temporization sleeves are snapped onto the abutments. (i) After placing harvested autogenous bone over the implants, the site is sutured closed.

Immediately loaded

Immediately loaded implants are intended to provide immediate function and aesthetics during the implant’s osseointegration. The immediately loaded technique is similar to the single-stage technique mentioned above, except that instead of a transmucosal abutment, a permanent abutment is used along with a provisional prosthesis, which provides the necessary fixation of the abutment and implant.

The use of TRINIA, a metal-free restorative material, is recommended for the provisional stabilizing prosthesis because it can provide the necessary strength. Using computer-aided design/computer-assisted manufacturing (CAD/CAM), a provisional TRINIA stabilizing prosthesis is custom-made to include both the prosthesis and supporting wings or extensions, which are cemented or bonded to adjacent teeth (see chapter 11). The treatment discussed below illustrates the immediate placement and loading of four maxillary incisor implants in fresh extraction sockets with a TRINIA provisional stabilizing prosthesis; however, the principles discussed are applicable to all immediate loading procedures using TRINIA, including single-tooth

Box 8-4 Immediately loaded technique: Step-by-step guide

1. Expose the alveolar crest by creating a broad-based flap that preserves the papillae and attached tissue.

2. With the pilot drill, create an initial osteotomy that is 2 to 3 mm deeper than the final implant length, drilling at 1,100 rpm without irrigation.

3. Confirm the trajectory of the osteotomy with a paralleling pin or by inserting an abutment with a 2.0-mm post.

4. Use either Latch Reamers or Hand Reamers to widen the osteotomy.

• If using Hand Reamers, attach the 2.5-mm Hand Reamer to the rotary reamer and widen the osteotomy sequentially, at 0.5-mm increments, to the diameter of the intended implant.

• If using Latch Reamers, attach the 2.5-mm Latch Reamer to an electric drill system and widen the osteotomy sequentially, at 0.5-mm increments, rotating at 50 rpm, to the diameter of the intended implant.

5. During the reaming process, intermittently harvest any autogenous bone that accumulates in the reamer and place it in a dappen dish.

6. Use a spoon excavator to harvest any remaining bone debris.

7. Inspect the four walls and floor of the osteotomy to make sure they are intact.

• If the intended Temporary Abutment is wider than the osteotomy, use a larger-diameter reamer to create a countersink.

8. Remove the implant/Healing Plug from its sterile blister pack using an aseptic technique.

9. Remove the black Healing Plug and attach the implant to the Implant Inserter/Retriever instrument.

10. Place the implant in the osteotomy.

11. Insert the Universal Abutment into the implant well.

12. Minimally engage the locking taper by tapping gently.

13. Trim the temporization sleeve to the appropriate dimensions.

14. Snap the temporization sleeve onto the definitive abutment.

15. Cover the implant with the previously harvested autogenous bone from the dappen dish.

16. Optional: If a large flap has been made, suture the surrounding tissue to minimize the exposure of the abutment and alveolar crest.

17. Test the passive fit of the provisional prosthesis over the temporization sleeves, and make any necessary modifications to ensure an acceptable fit.

18. Optional: Use a fit-checker material (vinyl polyether silicone) to identify areas of tissue impingement, and modify the prosthesis accordingly.

19. Apply petroleum jelly to the sutures.

20. Apply cement to the bores and wings of the provisional prosthesis.

21. Attach the provisional prosthesis containing cement onto the temporization sleeves and adjacent structures, if applicable.

22. Light-cure the provisional prosthesis to the temporization sleeves and adjacent structures.

23. Polish the provisional prosthesis. 24. Wait for osseointegration to occur before placing the definitive prosthesis. Fig 8-30 Facial (a) and palatal (b) views of a TRINIA stabilizing prosthesis on a stone model. Support structures called wings are cemented to adjacent teeth to provide stability to the prosthesis during osseointegration.

Fig 8-31 Cement is applied to the bores and wings of the provisional prosthesis.

restorations. Before initiating the surgical implantation procedure, confirm the appropriate adaptation of the TRINIA stabilizing prosthesis.

After curetting the extraction sockets, osteotomies are prepared with or without a surgical guide (Fig 8-28). Figure 8-29 shows the initial steps of the immediate placement and loading of four implants; these steps are the same as those discussed in the single-stage and two-stage techniques and are outlined in Box 8-4. Before beginning the immediate loading procedure, a TRINIA provisional stabilizing prosthesis should be prepared by a laboratory technician (Fig 8-30). The CAD/ CAM TRINIA provisional stabilizing prosthesis is designed with wings, which are cemented to adjacent teeth to provide stabilization of the implants while they are undergoing osseointegration (Fig 8-31).

Although other materials may be used to fabricate a provisional stabilizing prosthesis, TRINIA is preferred for its excellent strength, light weight, and ability to readily bond to many dental materials. The passive fit and appropriate occlusal contacts of the TRINIA stabilizing prosthesis should be confirmed prior to initiating the osteotomies, again after the insertion of the Universal Abutments, and a third time after the modified temporization sleeves have been placed onto the Universal Abutments. After confirmation of a passive adaptation, petroleum jelly is applied over the sutures, and cement or composite material is applied to the bores and wings of the prosthesis in preparation for the cementing or bonding of the prosthesis (see Fig 8-31). Fig 8-32 (a and b) Postoperative facial and palatal views following cementation of the provisional prosthesis to the temporization sleeves and adjacent teeth. (c) Postoperative radiograph showing four immediately placed and loaded 4.0 × 6.0–mm implants with Universal Abutments and a stabilizing winged TRINIA provisional prosthesis. (d) Patient’s smile after placing the four Integrated Abutment Crowns (IACs).

To conclude the procedure, the provisional prosthesis is polished, and any final adjustments are made (Fig 8-32). It is of paramount importance to adjust the occlusal contacts and to ensure that the prosthesis will be stable throughout the months of osseointegration.

Guided surgery

Although Bicon’s guided surgery technique is straightforward and efficient, it is most often unnecessary even for newly trained clinicians. With Bicon’s 5.0-mm short and 3.0mm narrow implants, all areas of the edentulous alveolus can effectively be treated. Clinicians find it simple and convenient to place implants without the use of digitally generated surgical guides; however, in certain circumstances, as in the treatments described below, the technique can be practical for clinicians unfamiliar with the Bicon implant system and even for experienced clinicians. Through the use of cone beam computed tomography (CBCT), clinicians can place and position implants virtually prior to the actual surgical procedure. Using specialized surgical planning software, the laboratory can then translate the implant’s virtual position into a surgical guide.

Initial radiographs should be used to determine if guided surgery is more beneficial for a given patient. A fullmouth CBCT scan and any additional radiographic studies recommended by the surgical guide fabricator should be obtained. Although a thorough explanation of CBCT techniques and software operation for guided surgery is beyond the scope of this chapter, a brief explanation is as follows: After adding three-dimensional representations of Bicon implants to the scanning software, an appropriately sized implant is chosen for the intended implant site. The implant should be positioned within the software so that it lies within 10 degrees of the angulations of adjacent teeth; this will allow for the use of a straight abutment and avoid compromising prosthetic outcomes. After finalizing the positioning of the implant within the software, a scan is sent to the guide-fabricating laboratory along with any models and supporting materials.

After receiving the fabricated surgical guide from the laboratory, its fit and stability must be verified intraorally (Fig 8-33a). Once the stability of the surgical guide has been verified, a Tissue Punch is used to mark the osteotomy site and possibly to expose the alveolar crest; however, if there is a minimal amount of keratinized tissue, a scalpel should be used to make a properly designed access flap in the interest of conserving an adequate zone of attached gingiva (Fig 8-33b). If a Tissue Punch is used, the circular piece of mucosa that is removed should be kept moist so that it can be replaced after placement of the implant. A Spade Drill is used to prepare the initial osteotomy; rotating at 400 rpm without irrigation, the drill is advanced into the surgical guide until it contacts the color-coded ring (Fig 8-33c). To advance the osteotomy, longer Guided Reamers are used sequentially until the final implant length is reached (Fig 8-33d). These reamers are rotated at 50 rpm, and any autogenous bone accumulating in the reamers is harvested into a dappen dish for later use. Fig 8-33 (a) Testing the fabricated guide in the patient’s mouth to ensure a stable fit. (b) When minimal keratinized tissue is present, a properly designed flap should be used to expose the alveolar crest. (c) A Spade Drill rotating at 400 rpm without irrigation is used to prepare the osteotomy. The drill is advanced into the surgical guide until it contacts the color-coded ring. (d) Latch Reamers rotating at 50 rpm are used sequentially until the final implant length is achieved. Any autogenous bone that accumulates on the reamer should be harvested for later use. (e) A Guided Inserter is used to place and seat the implant. (f) The fabricated surgical guide is removed. (g) The black Healing Plug is inserted into the implant well. (h) Appearance of a trimmed black Healing Plug in the implant well. (i) Autogenous bone harvested during latch reaming is applied to the implant. (j) After the conclusion of the guided surgery procedure, the tissue flap is closed.

When the desired depth and width have been reached, the implant is placed in the osteotomy using the Guided Inserter or another instrument (Fig 8-33e). The fabricated guide is then removed, and the black Healing Plug is inserted (Figs 8-33f and 8-33g). The Healing Plug can be trimmed prior to its insertion or inserted whole and trimmed while in the implant; either method is permitted as long as the resulting surface is even and has no sharp edges (Fig 8-33h). At this stage, any harvested autogenous bone is placed to cover the entire implant (Fig 8-33i). To conclude the surgery, the flap is closed or the circular Tissue Punch-out is sutured in place over the implant (Fig 8-33j).

After the appropriate period of time has elapsed for osseointegration, the surgical guide can be used with the Tissue Punch or scalpel to mark the site for the uncovering of the implant. The same procedural steps outlined for the two-stage technique in the step-by-step quick guide found in Box 8-4 can be followed to complete the procedure. A step-by-step quick guide for guided surgery can be found in Box 8-5.

Box 8-5 Guided Surgery: Step-by-step guide

1. Test the fabricated surgical guide to ensure proper fit (take a radio12. To uncover the implant, take a scalpel and make a semilunar incigraph if necessary). sion that exposes the implant in the aesthetic area and creates a

2. Expose the alveolar crest. split-thickness flap.

• If keratinized tissue is normal, use the Tissue Punch. Save the punched-out tissue on a sterile wipe wetted with sterile water.

• If keratinized tissue is minimal, create a tissue flap with a scalpel.

• 3. Using the Spade Drill at 400 rpm without irrigation, advance the drill until contact is made with the color-coded ring in the surgical guide, and then stop.
• 4. Use Latch Reamers sequentially (from shortest length to longest), rotating at 50 rpm without irrigation. Collect any bone that accumulates on the reamers.

5. Place the implant using the Guided Inserter or other similar tool. 6. Remove the fabricated surgical guide and save it. 7. Trim the black Healing Plug and insert it into the implant well. 8. Cover the implant and inserted black Healing Plug with the autogenous bone that was gathered during the latch reaming stage.

6. Close the flap or reattach the Tissue Punch-out. 10. Allow osseointegration to occur for a time period indicated by bone type. 11. Use the surgical guide and Tissue Punch to facilitate locating the implant.

7. Remove any bone that has grown over the implant.

8. Insert a guide pin into the implant well and check the integration and angulation of the implant.

9. Attach a Sulcus Former (with the same diameter as the desired abutment) to a straight handle.

10. Guide the sulcus reamer onto the guide pin, and rotate it to remove any tissue that may impinge the definitive abutment.

11. Flush the well with water.

12. Insert the abutment into the implant well.

13. Engage the locking taper by tapping gently. 20. Place an Emergence Cuff or temporization sleeve onto the abutment.

14. Inject acrylic around the Emergence Cuff or temporization sleeve. 22. Inject acrylic into the vacuum-formed template.

15. Place the vacuum-formed template on the abutment. 24. Polish the acrylic so that it becomes confluent with the Emergence Cuff or temporization sleeve.

16. Wait for the soft tissues to heal prior to taking a final impression.

or all of the following recommendations. It is the clinician’s responsibility to determine whether or not the guidelines presented here are appropriate for a specific patient.

Maxilla

Fig 8-34 A custom-made thermoplastic seating jig is used to seat a maxillary anterior crown in the long axis of the implant.

Clinical Recommendations

After familiarizing oneself with the basic treatmentplanning and surgical procedures described above, it is advisable to become acquainted with the nuances and challenges presented by individual implant locations and their respective anatomies. The following sections will provide location-specific recommendations that have been gleaned over the past 31 years. It should be noted that the recommendations provided herein should serve only as a guide and not as a rule for all patients. Individual patient attributes may preclude the implementation of some

Bicon implants placed in the location of central incisors should be placed slightly to the distal of the midline to avoid inadvertently entering or perforating the incisive canal. The long axis of the implant should bisect the buccolingual plane at a perpendicular angle to allow it to be centered on the incisal edge of the intended tooth. If placed correctly, a straight abutment can be used and will allow for an even distribution of restorative material to be applied to both the buccal and lingual sides of the restoration, enhancing the aesthetic result. If this cannot be achieved, it may be necessary to use an angled abutment, in which case an ideal result may not be possible.

Maxillary anterior implants, especially with angled abutments, necessitate the use of a custom-made seating jig to definitively seat the crown/abutment (Fig 8-34). Instructions for fabricating the seating jig and in-depth instructions for its use can be found in chapter 11. Because maxillary anterior implants play such an important role in the patient’s life—both functionally and psychologically—their placement and restoration with proper seating techniques are of paramount importance; therefore, a checklist has been included to maximize their success (Box 8-6). After reviewing the pertinent section of chapter 11, the checklist can be used as a guide prior to seating a definitive restoration of a maxillary anterior implant.

Box 8-6 Maxillary anterior seating checklist

Planning

• Establish an appropriately stable anterior and posterior occlusion to avoid the possibility of inadvertently loosening the maxillary anterior abutment.

• Ensure that the trajectory of the pilot drill osteotomy approximates the long axis of the adjacent teeth.

Handling

• Follow the proper protocols when handling the implant and abutment.

• Remove any possible contaminants with a Cotton-Tip Applicator treated with ethanol. Blood, glove powder, and plastic detritus can all reduce the amount of torque needed to unseat the abutment.

Seating and tapping

• Eliminate or control bleeding using a combination of vasoconstrictors, pressure, and time.

• Clean the abutment post and implant well with an alcohol wipe.

• Insert and align the abutment/crown (use an incisal orientation jig when necessary).

• While supporting the bridge of the patient’s nose, apply the seating tap. Use the custom-made seating jig to ensure that the seating forces are being directed through the long axis of the implant.

• Confirm passive interproximal contacts with floss. If contacts need to be adjusted, remove the crown or use a thin metal finishing strip.

• Provide six additional seating taps.

• Reconfirm contacts.

Preparation for seating

• Fabricate the seating jig around the definitive crown using the Crown-Alignment Device and thermoplastic resin.

• Perform a preliminary insertion using only finger pressure (this is only an initial evaluation to determine if anything interferes with passive seating).

• Remove any interference or excessive interproximal contact (eg, soft tissue, interproximal tooth contact).

• Adjust any contacts until dental floss can be passed through with minimal resistance.

Evaluation and adjustment

• Check the occlusion. Establish uniform contacts initially in maximal intercuspation and then in protrusive and retrusive excursions.

• Adjust contacts while the patient clenches. Establish uniformly balanced contacts while the patient is clenching in all extreme excursions, including retrusive movements of the mandible from an extreme protrusive position.

• Confirm the removal of bony interferences and proper seating with a radiograph. Fig 8-35 The location of the inferior alveolar nerve.

Radiographs should be taken to positively identify the location of the maxillary sinus and nasal floor before proceeding with any surgical procedure to avoid the inadvertent penetration of either of these structures. Long periods of edentulism, variations in morphology, or consequences of disease or injury often reduce the available bone height of the maxilla, which frequently necessitates performing a minimal sinus elevation procedure (see chapter 12). Fig 8-36 The location of the mylohyoid line and the submandibular fossa.

Mandible

When placing implants in the mandible, extra care must be taken to avoid the inferior alveolar nerve and the mental foramen (Fig 8-35). In addition, a clinician must avoid penetrating the submandibular fossa located below the mylohyoid line (Fig 8-36). Particularly, attention should be paid to the sublingual space in the anterior mandible where the sublingual artery is located to avoid life-threatening bleeding. Appropriately directing the pilot bur and reamer burs toward the buccal and monitoring the area with digital contact during drilling can help prevent the inadvertent penetration of the lingual plate.

Mandibular premolar locations are typically characterized by limited amounts of facial bone; therefore, when the implant is placed in a premolar extraction site, it should be placed slightly more lingually and 3 to 4 mm below the facial crest of bone, if practical.

depth step-by-step instructions have been provided for the single-stage surgery, two-stage surgery, guided surgery, and immediately loaded techniques. Subsequent chapters in this book cover more advanced techniques and cases of unusual anatomy or disease states. In addition to these chapters, there are numerous training videos, webcasts, manuals, and other resources available online at www.bicon.com, which should be mastered before attempting anterior implant placement or in sites with minimal bone.

Conclusion

Reference

The topics presented in this chapter, in addition to practical training, should give clinicians the knowledge required to confidently perform the basic surgical procedures of the Bicon implant system where there is ample bone. In-

1. Giro G, Marin C, Granato R, et al. Effect of drilling technique on the early integration of plateau root form endosteal implants: An experimental study in dogs. J Oral Maxillofac Surg 2011;69:2158–2163.

09

Anterior Implant Placement

Shadi Daher | Muneki Hirayama | Mauro Marincola | Laura Murcko | Luca de Micheli | Joseph Leary

The human smile plays an essential role in nonverbal communication, from conveying positive emotion to masking malevolent intent in certain social situations.[1] It has been suggested that the perceivers, or recipients of a smile, are highly sensitive to almost imperceptible delineations in the bearer’s intents.[2,3] In modern-day Western society, a harmonic, symmetric smile is considered a signal of reliability and influences the bearer’s perceived physical attractiveness.[4–9] The aesthetic zone, the teeth and gingiva visible upon presentation of a smile, is a major component of the human smile.

In addition to interfering with the subtleties of nonverbal communication, missing or damaged anterior teeth have been shown to negatively impact relationships, employment, self-image, and overall quality of life.[4,10–20] Therefore, effectively restoring the function and aesthetics of anterior teeth is of paramount importance; because of the hidden psychosocial costs associated with missing anterior teeth, modalities aimed at restoring functionality and aesthetics have far-reaching effects on the patient’s general well-being.[10–16]

Dental implants are an effective method of restoring the functionality and aesthetics of missing teeth.[21,22] Dental implants ≤ 8.0 mm in length are called short implants . Because of their short length, these implants can be placed in locations that would otherwise require invasive procedures such as bone augmentations or in some cases run the risk of life-threatening complications, such as perforating the lingual cortical plate.[22–25]

Owing to their surrounding anatomy, the anterior maxilla and mandible are locations that frequently necessitate major ancillary procedures when placing implants. Because of the proximity of the anterior maxilla to the nasal floor, implants with conventional lengths ≥ 8 mm frequently require grafting procedures, especially after long periods of edentulism.[22,26] Similarly, the mandible presents its own set of anatomical challenges. The interproximal spacing of natural mandibular teeth is condensed, making attempts to restore natural and aesthetic papillae challenging where implants are concerned. Additionally, the tissue apical to the lingual cortical plate is highly vascular; perforating the lingual cortical plate runs the risk of damaging the sublingual artery, causing hemorrhaging that can be life threatening to occur. This is especially hazardous in implants with lengths ≥ 15 mm.[27–29] Fig 9-1 (a) Paralleling pins positioned in maxillary pilot osteotomies. (b) Image reveals scalloped flap incision, retraction sutures, and Healing Plug being inserted into the well of an implant.

Restoring missing anterior teeth has a large impact on the patient’s well-being; because of this, it is important for clinicians to provide their patients with an implant system that offers reliable function and aesthetics. The Bicon dental implant system offers short implants that utilize a locking taper to secure the abutment to the implant. The macrogeometry and overall reduced length of Bicon implants helps to avoid many of the problems associated with anterior implant placements. As mentioned, the shortened length of Bicon implants reduces the need for ancillary procedures such as bone augmentation procedures and helps to avoid the vascularized tissues apical to the lingual cortical plate. Furthermore, the sloping shoulder at the neck of the Bicon implant provides space for the development of healthy and aesthetic papillae even for mandibular incisors.

Although Bicon implants are easy to use, their placement in the anterior maxilla and mandible presents certain technical challenges. To be successful when placing anterior implants, there are nuances to be observed and pitfalls to be avoided. This chapter presents tips and recommendations that have been gleaned from over hundreds of years of collective clinical experiences to assist clinicians in the placement of Bicon implants in anterior sites.

General Recommendations for Anterior Implant Placement

Surgical procedures and placement

In general, the surgical procedures outlined in chapter 8, such as slow reaming of the osteotomy and positioning the implant

2 to 3 mm below the crest, should always be followed when placing implants in anterior locations. However, it may be aesthetically and restoratively more acceptable to position the implant up to 5 mm below the bony crest if sufficient mucosa is available.

Ideally, all incisions should be made on the palatal or lingual slope of the crest of the ridge; this will allow adequate blood circulation to the interdental papillae and avoid unsightly scarring (Fig 9-1). Location-specific surgical guidelines can be found in Tables 9-1 and 9-2. When placing multiple threaded or cylindric implants in anterior locations, the clinician must ensure that there is 2.5 to 3.0 mm of space between implants, whereas with the sloping shoulder design of the Bicon implant, less than 2.0 mm of spacing is acceptable for the formation of natural interproximal papillae.

Angulation and positioning

If an anterior implant is to be placed between two teeth that are reasonably well aligned and in an appropriate occlusal position, then a simple visualization or bisecting the line technique may be used to help locate the best position for the rotary cutting instruments. To perform this technique, visualize a horizontal line between the adjacent teeth. The position of the rotary cutting instruments should be at the middle of the imaginary line (Fig 9-2).

When placing implants in the anterior sextants, it is of paramount importance that the trajectory of the implant be parallel to the trajectory of the adjacent teeth. Whenever possible, implants should be placed as close as possible to the palatal or lingual cortices without risking a perforation. This not only provides initial stability by engaging thicker bone but also enhances long-term stability by avoiding the effects of normal buccal plate remodeling. After 20 years of normal remodeling of the facial bone, the metallic appearance of the implants is evidenced (Fig 9-3). Having thicker hard and soft tissues on the facial side of the implant can minimize the risk of exposing the metal of the implant body or abutment over the long term.

When placing an implant into a tooth socket, the initial trajectory of the pilot drill should be aimed into the palatal bone of the socket at the middle to apical third of the depth

Table 9-1 Maxillary anterior implant placement guidelines Table 9-2 Mandibular anterior implant placement guidelines of a normal socket with an initial angle that is more or less perpendicular to the trajectory of the intended restoration (Fig 9-4a). Once the pilot drill engages the bone, the angle of the drill must be changed so that its trajectory becomes parallel with the adjacent teeth and the proposed restoration (Fig 9-4b). More detailed and site-specific information concerning osteotomy preparations in anterior locations can be found below. Fig 9-3 Note the metallic appearance of the implant through the facial mucosa as a result of buccal bone resorption over the span of 20 years that the implants have been in function.

Fig 9-2 Bisecting the line technique: Rotary cutting instruments are positioned in the middle of an imaginary horizontal line between the adjacent teeth.

Immediate placement

After extracting a tooth, the resulting alveolar socket should be curetted well. Once the osteotomy walls are shown to be intact and free of granulation tissue and/or defects, an implant may be placed. To immediately place an anterior implant, the pilot drill should be placed at a 45degree angle and advanced in such a manner that it engages the palatal wall of the socket as described above. Once the bone is slightly perforated, the drill is immediately reoriented to be parallel with adjacent teeth and is advanced approximately 3 mm vertically into the palatal bone. After the trajectory is verified radiographically with a paralleling pin or with the pilot drill as a marker, the pilot drill can be advanced to the full depth of the osteotomy. At this point, the pilot osteotomy position and angulation must be verified again to ensure their accuracy.

When using Latch Reamers, firm control of the handpiece must be maintained, often while applying a slight horizontal pressure to prevent its being displaced by the denser palatal plate while simultaneously applying apical pressure to advance the drill to the desired depth. When gauging the depth of an immediate implant placement in the maxilla, it may be advantageous to measure from the edge of the facial gingiva and not from the crestal bone level. If 3.0 mm is added to the estimated drilling depth to account for the soft tissue height, it will not only take into account the varying thickness of the gingival margin but also allow for potential resorption of the crestal bone. For example, a 6.0-mm-long implant placed 2.0 mm beneath the crest, plus 3.0 mm for the soft tissue thickness, results in an initial drilling depth of 11.0 mm from the facial gingiva.

Fig 9-4 (a) The initial trajectory of the pilot drill. (b) After engaging the bone, the angle of the pilot drill is adjusted to align its trajectory with the adjacent teeth.

For canine locations, an 8.0-mm-long implant with a 2.5mm well is often recommended for two reasons: First, the 2.5-mm well is specifically designed to withstand the higher rotary forces encountered in the anterior maxilla; second, the 8.0-mm length allows for improved positioning of the implant shoulder because the implant has to be placed deeply enough in the socket to achieve a reasonable measure of stability. Because of the maxillary canine’s root anatomy, most of the implant’s surface will not come into contact with the socket’s alveolar wall. Often, only the apical 2 to 3 mm of the implant will engage the osteotomy, which is sufficient to provide adequate initial stability. The osseointegration of Bicon implants begins with the formation of a callus , the blood clot that is the precursor of the Haversian bone that will form over time. Therefore, it is imperative to prevent the loss of the callus through the daily functions of the oral cavity, particularly the part of the callus over the implant’s shoulder.

There are several methods of preventing both the migration of the crestal soft tissues into the osteotomy and the displacement and loss of the newly forming callus. For the two-stage technique, either the use of a commercially available resorbable collagen plug or an autogenous leukocyte- and platelet-rich fibrin (LPRF) plug generated from the patient’s own blood offers a convenient means of achieving closure without raising an additional mucoperiosteal flap. For the single-stage nonloading and immediate loading techniques, using a Temporary Abutment or a Universal Abutment with a provisional crown will protect and stabilize both the crestal soft tissues and the callus. In most cases, immediately placed implants should be put in function only after a 3-month healing period unless they were prosthetically stabilized for immediate function.

Delayed-immediate approach

The delayed-immediate approach is an alternative to immediate placement. This approach, which calls for a 6- to 8-week postextraction healing period, should be pursued if one of the following circumstances is present: the health of the implant site is less than ideal, the provisionalization requires lengthy preparation and is suboptimal, or the extraction of the tooth was traumatic.

Additionally, the decision to immediately place implants or take a delayed-immediate approach is based on how much facial bone remains on the wall of the socket. If there is extensive damage to the socket following the extraction, it is prudent to do a delayed-immediate approach or a delayed approach with 4 to 6 months of healing with socket regeneration techniques before placing an implant (see chapter 19).

Where there is marked scalloping of the socket opening, the best treatment is a delayed technique. Such an approach eliminates any uncertainty regarding the final buccal plate height, including the possibility of placing the implant too deep relative to the interproximal and palatal bone. Although it is possible to restore implants that have been placed deeper than is normal, it can be challenging.

Maxillary Anterior Implants

Central incisors

When immediately placing implants postextraction, it is important to prepare the osteotomy correctly with regard to initially engaging the palatal slope with the pilot drill and by placing the implant at the correct depth and angle. The size and location of the incisive foramen and canal should also be determined, and steps should be taken to avoid these structures. The nasal floor should also be avoided; however, in extreme cases, it can be lifted up to 3 mm using a nasal elevation technique.[30]

Incisions through the incisive papilla should be made in a tangential fashion around its posterior perimeter; this avoids transecting the vessels and compromising the aesthetic outcome. It is important to pay close attention to the angulation of both the osteotomy and the implant. Ideally, when a straight abutment is placed into the implant, it should be just facial to the incisal edge of the opposing mandibular incisor. Placing implants in a healed site using a delayed-immediate or delayed approach has many similarities to immediate placement of implants; accordingly, all of the above recommendations apply with a few exceptions. Semilunar incisions that allow for a palatal-based flap are recommended for healed sites. After the preparation of the implant osteotomy, pay close attention to the thickness of the buccal bone: A minimum of 2.0 mm is recommended. If the minimum amount of buccal bone is not available, then grafting is recommended. The clinician should consider whether there is an inadequate alveolar dimension before initiating any implant placement surgery so that performing a ridge-splitting procedure is retained as a viable option.

Lateral incisors

The recommendations for immediately placed maxillary implants in central incisor locations also apply to lateral incisor locations, with two slight differences. First, the incisive foramen will not affect the preparation and placement of lateral incisor implants. Second, the trajectory of the lateral incisor root frequently carries its socket more to the palatal; this results in a socket with a thicker buccal plate, which in turn facilitates placement of the implant within the full depth of the socket.

Recommendations for the placement of implants in healed sites are similar to those for central incisors; however, the lateral incisor anatomy can typically accommodate only the 4.0-mm-diameter implant; nevertheless, clinicians should consider placing 4.5-mm-diameter implants whenever possible.

Canines

From the standpoint of surgical anatomy, the buccal plate is typically more curved at the canine root position. Also, the curve in the arch makes the angulation of the implant even more challenging because the adjacent teeth are also involved in the curving arch to some degree, making alignment of the implant more complicated. Canine restorations often bear the brunt of occlusal loading (canine guidance) with mandibular movements. When placing implants in healed sites, it is generally not advisable to use a ridge-splitting technique for the placement of a single implant because of the curvature of the buccal plate. This is covered in greater detail in chapter 13. Implant size recommendations for the maxillary anterior locations can be found in Table 9-1.

Mandibular Anterior Implants

Central and lateral incisors

Unlike in the maxilla, with the placement of implants in mandibular central and lateral incisor locations, the pilot bur must proceed through the apex of the socket because there is little lingual bone to receive the implant body. Because of space limitations, great care must be taken when preparing the osteotomy to prevent damage to the roots of the adjacent teeth or their bony support.

Because of their general dimensions of limited space, healed mandibular anterior sites are more likely to require buccal bone grafting. Moreover, mandibular anterior sites may require a fixed partial denture restoration, which allows for better spacing of the proposed implants (see Table 9-2).

Canines

Immediately placed and delayed implants in mandibular canine locations carry many of the same recommendations as for central and lateral mandibular incisors. Because of the canine roots and the corresponding width of the alveolus, 4.0- and 4.5-mm-diameter implants can be placed and are recommended, especially when a fixed partial denture restoration is planned. The canine location is usually the most favorable site for implants that will support an overdenture or a TRINIA fixed telescopic restoration.

Bicon 3.0-mm narrow implants with a 2.0-mm well diameter were designed ideally for mandibular anterior locations; however, other implant sizes are also acceptable. Implant size recommendations for mandibular anterior locations can be found in Table 9-2.

Anterior Restorations

Maxillary anterior restorations require the use of a special custom-made seating jig to facilitate the definitive engagement and seating of an Integrated Abutment Crown (IAC), extraoral cemented crown restoration, or an angled abutment. Briefly, a custom-made seating jig is fabricated to ensure that the seating forces used to engage the locking-taper connection between an abutment and an implant are directed along the long axis of both the implant and the shaft of the abutment. Detailed instructions concerning the fabrication and use of a seating jig can be found in chapters 8 and 11.

Occasionally, a freestanding maxillary anterior restoration will loosen; the causes for the loosening are most often related to inadequate understanding of the proper clinical protocols for using freestanding Bicon implants in the anterior maxilla. The following observations will help clinicians understand and successfully use Bicon implants in the anterior maxilla.

• Restore the patient’s posterior occlusion prior to placing an unsplinted maxillary anterior implant. Failure to ensure adequate posterior support will likely result in excessive occlusal forces on the anterior segment, possibly leading to loosening of the abutment.

• Use a custom-made seating jig to direct the seating forces along the long axis of the implant and abutment shaft.

• Confirm the complete and definitive seating of the abutment.

• With articulating paper in place and the teeth closed together in a somewhat clenched position, have the patient slowly move the mandible forward to a protrusive position, then slowly back into a retrusive position. Next, again with teeth in a closed, somewhat clenched position, have the patient move the jaw in right and left lateral excursions and evaluate and adjust every incisal contact detected. An occlusal interference will usually occur and be visible on the facial surface of the maxillary crowns, which indicates that the crown is too thick and not necessarily too long.

• During the movement from protrusive to retrusive, an occlusal interference will often appear on the facial surface of the implant crown. This indicates that the crown may be too thick and not necessarily too long.

• Using floss, evaluate the interproximal contacts to be certain they are intact and acting passively to counteract rotational forces.

• Periodically retap any restoration that has loosened

• more than once.

• Do not resort to cementing a loosened abutment into the well of the implant.

• Note that splinted restorations never loosen.

• If the loosening becomes recalcitrant, tap a “virgin” abutment directly from its packaging into a clean and dry implant well and proceed with an abutment-level transfer impression for the fabrication of a new restoration.

Clinical Illustrations

The following treatments demonstrate the application of the foregoing principles when using the Bicon implant system in anterior locations.

Treatment 1: Immediately placed maxillary anterior implant restored with an IAC

• Modify any extruded mandibular anterior tooth that

• may interfere with the restoration.

• When placing the implant, be sure it is in the same trajectory as the adjacent teeth so that the occlusal load is shared by all of the teeth in the anterior segment and the implant restoration does not act as a lever arm.

• Avoid placing an implant if adjacent teeth have significant mobility.

• Use an implant with a 2.5-mm well because it provides greater resistance to rotary forces.

The treatment of a 37-year-old woman whose maxillary left central incisor had a failed endodontic treatment can be seen in the following images. The incisor and granulation tissue were removed (Figs 9-5a to 9-5d). A 2.0-mm pilot drill was inserted into the fresh socket to begin the initial osteotomy, and a paralleling pin was then placed to evaluate the trajectory (Figs 9-5e and 9-5f). Once the trajectory was confirmed, the osteotomy was enlarged using a succession of widening Latch and Hand Reamers (Fig 9-5g). Bone accruing in the flutes of the reamers was collected in a dappen dish for later use (Fig 9-5h). Fig 9-5 (a and b) Clinical image and preoperative radiograph of a 37-year-old woman with a failed endodontically treated maxillary central incisor. (c) Infected tooth being removed. (d) Granulation tissue being removed with a curette. (e) Note the trajectory of the 2-mm pilot drill being used to prepare the osteotomy. (f) A paralleling pin placed into the osteotomy to evaluate its trajectory. (g) The osteotomy being widened with a 2.5-mm Latch Reamer. (h) Bone accumulated in the flute of a 5-mm Hand Reamer is saved for grafting over the implant. (i) A 5.0 × 8.0–mm implant is placed into the osteotomy using the Inserter/Retriever instrument. (j) A black Healing Plug is placed into the implant well. (k) Harvested bone being placed over the implant. (l) Resorbable collagen plug being placed over the osteotomy. (m) The collagen plug and harvested bone secured with a suture.

After confirming the integrity of the osteotomy, a 5.0 × 8.0–mm implant was placed with the Inserter/Retriever Instrument mounted on a straight handle (Fig 9-5i). A trimmed black Healing Plug was placed into the implant, and bone harvested during the procedure was spread over the shoulder of the implant (Figs 9-5j and 9-5k). The harvested bone was covered and secured in the osteotomy with a resorbable collagen plug, and the site was sutured (Figs 9-5l and 9-5m). Following the placement of the collagen plug, a provisional crown was bonded to the adjacent teeth (Fig 9-5n), and a Fig 9-5 (cont) (n) A provisional crown was bonded in place. (o) Postoperative radiograph. (p) Image of IAC. (q) Two-week postplacement radiograph. (r) Two-week postplacement smile. Fig 9-6 (a and b) Preoperative clinical image and radiograph of mandibular central incisor. (c) Tooth being extracted. (d) Osteotomy being widened with a 2.5-mm Hand Reamer attached to a Latch Instrument extender. —>

postoperative radiograph was taken to confirm the implant’s position (Fig 9-5o). The IAC and postplacement radiograph are shown in Figs 9-5p to 9-5r.

Treatment 2: Extraction and immediate placement in site of mandibular central incisor

A 69-year-old woman presented with a fractured mandibular right central incisor (Figs 9-6a and 9-6b). The incisor was extracted, and the osteotomy was prepared (Figs 9-6c and 9-6d). Bone harvested during the reaming procedure was saved in a dappen dish for later use (Fig 9-6e). After confirming the integrity of the floor and walls of the osteotomy, a 3.0 × 8.0–mm implant was placed (Fig 9-6f). After definitively seating the implant, the harvested bone was placed over the implant, and the site was sutured (Figs 9-6g and 9-6h).

After 3 months of healing, the site was opened and the implant uncovered (Figs 9-6i and 9-6j). To confirm the implant’s trajectory, a guide pin was placed into the implant well (Fig 9-6k). The site was cleaned, and the IAC prosthesis was placed (Figs 9-6l and 9-6m). At the 2-year follow-up, the interdental papillae had matured to a natural and aesthetic appearance (Fig 9-6n).

i

Fig 9-6 (cont) (e) A 3.0-mm Hand Reamer widening the osteotomy. Harvested bone is saved in a dappen dish. (f) A 3.0 × 8.0–mm implant being placed into the osteotomy. (g) Implant being definitively seated with a 2.0-mm seating tip. (h) Sutured site after placement of harvested bone over the implant. (i) Implant site being uncovered after 3 months of healing. (j) Black Healing Plug being removed during the uncovering. (k) Guide pin being used to confirm the implant’s trajectory. (l) Clinical appearance of the definitive restoration. (m) Postplacement radiograph of the IAC. (n) Note the natural and aesthetic appearance of the interdental papillae at the 2-year postplacement evaluation.

Treatment 3: Implant restoration with aesthetic soft tissue

A 64-year-old man with periodontal disease wished to improve the appearance of his maxillary anterior teeth without extensive surgical procedures. After meticulous periodontal treatment, there was generalized improvement and a return to periodontal health with the exception of the maxillary left central incisor. The incisor had residual probing depths of 7 to 8 mm, bleeding on probing, and vertical and horizontal mobility. The initial radiograph shows the advanced bone loss (Fig 9-7a). The aesthetic challenges included the loss of contact between the central incisors and the recession of the papillae between the central and lateral incisors. Additionally, upon close inspection, one can see the collapse of the facial mucogingival tissues masking the loss of facial bone over the central incisor. Finally, there are a number of stained and defective cervical restorations (Fig 9-7b).

The periodontally involved maxillary incisor was extracted, and both the soft and hard tissues reveal the postextraction aesthetic issues (Figs 9-7c and 9-7d). Three weeks later, a short 4.0 × 6.0–mm implant with a 2.5-mm well was placed (Fig 9-7e). The implant was uncovered after 5 months of healing, and as planned, the mucogingival thickness deficit was corrected by placing a connective tissue graft over the facial aspect of the implant (Figs 9-7f and 9-7g). Following the graft placement, a polyetheretherketone (PEEK) Healing Abutment was placed (Fig 9-7h). Fig 9-7 (a) Radiograph of endodontically treated maxillary left central incisor, with 7- to 8-mm probing depths and vertical and horizontal mobility. (b) Clinical image of inflamed gingiva, diastema between the central incisors, extruded left central incisor, generalized recession, and loss of interproximal tissue. (c and d) Postextraction site image and radiograph after 3 weeks. (e) Radiograph of 4.0 × 6.0–mm 2.5-mm-well short implant placement 3 weeks postextraction. (f) Five months later, a soft tissue graft was placed to thicken the facial tissues over the implant. (g) Soft tissue graft in place. (h) PEEK Healing Abutment in place. (i) Impressions and provisional abutment crown placed after 1 month. (j) Clinical image of gingivectomy of right central and lateral incisors. (k and l) Image and radiograph of porcelain-fused-to-metal crown placed on left central incisor 3 months after the placement of provisional crown.

One month after the uncovering, impressions were taken, an abutment and a provisional crown were placed, and the defective cervical restorations were replaced (Fig 9-7i). At a subsequent visit, restorative material was added to the mesial aspect of the right central incisor to mimic the shape of the provisional implant restoration, and the contact points between the central incisors were raised. Finally, the gingival margins of the right central and lateral incisors were balanced with a gingivoplasty (Fig 9-7j).

It is important to note that there must be a waiting period to allow the soft tissue to adapt to the shape of the provisional crown, the modified right central incisor, and the rounded base of the implant abutment. After 3 months, the soft tissues adapted, and the provisional crown was replaced with a definitive porcelain-fused-to-metal crown (Figs 9-7k and 9-7l).

When established methods for aesthetic rehabilitation, or what may be called camouflage techniques , are carried out consistently and in well-defined and timely sequences, the clinician can routinely achieve predictable success.

Conclusion

The importance of anterior teeth is undeniable; they play significant roles in speaking, mastication, smiling, psychologic expression, and perceived notions of physical attractiveness. Restoring missing or damaged anterior teeth has a profound impact on a patient’s well-being. This chapter has reviewed some of the challenges present when placing Bicon implants in anterior locations; by becoming familiar with these techniques, clinicians can avoid pitfalls and provide long-term function and aesthetics for their patients.

References

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2. Miles LK. Who is approachable? J Expl Soc Psychol 2009;45:262–266.

3. Maringer M, Krumhuber EG, Fischer AH, Niedenthal PM. Beyond smile dynamics: Mimicry and beliefs in judgments of smiles. Emotion 2011;11: 181–187.

4. Lauria A, Rodrigues DC, de Medeiros RC, Moreira RWF. Perception of oral and maxillofacial surgeons, orthodontists and laypersons in relation to the harmony of the smile. J Craniomaxillofac Surg 2014;42:1664–1668.

5. Grammer K, Fink B, Møller AP, Thornhill R. Darwinian aesthetics: Sexual selection and the biology of beauty. Biol Rev Camb Philos Soc 2003;78: 385–407.

6. Matoula S, Pancherz H. Skeletofacial morphology of attractive and nonattractive faces. Angle Orthod 2006;76:204–210.

7. Noman AV, Wong F, Pawar RR. Canine gouging: A taboo resurfacing in migrant urban population. Case Rep Dent 2015;2015:727286.

8. Morris AG. Dental mutilation in southern African history and prehistory with special reference to the “Cape Flats Smile”. SADJ 1998;53:179–183.

9. Scott BJ, Leung KC, McMillan AS, Davis DM, Fiske J. A transcultural perspective on the emotional effect of tooth loss in complete denture wearers. Int J Prosthodont 2001;14:461–465.

10. Nickenig HJ, Wichmann M, Terheyden H, Kreppel M. Oral health-related quality of life and implant therapy: A prospective multicenter study of preoperative, intermediate, and posttreatment assessment. J Craniomaxillofac Surg 2016;44:753–757.

11. Casanova-Rosado JF, Medina-Solis CE, Vallejos-Sánchez AA, Casanova-Rosado AJ, Maupomé G, Avila-Burgos L. Lifestyle and psychosocial factors associated with tooth loss in Mexican adolescents and young adults. J Contemp Dent Pract 2005;6:70–77.

12. Strauss RP, Hunt RJ. Understanding the value of teeth to older adults: Influences on the quality of life. J Am Dent Assoc 1993;124:105–110.

13. Yu SJ, Chen P, Zhu GX. Relationship between implantation of missing anterior teeth and oral health-related quality of life. Qual Life Res 2013;22:1613–1620.

14. Al-Omiri MK, Karasneh JA, Lynch E, Lamey PJ, Clifford TJ. Impacts of missing upper anterior teeth on daily living. Int Dent J 2009;59:127–132.

15. De-Marchi LM, Pini NIP, Ramos AL, Pascotto RC. Smile attractiveness of patients treated for congenitally missing maxillary lateral incisors as rated by dentists, laypersons, and the patients themselves. J Prosthet Dent 2014;112:540–546.

16. Henson ST, Lindauer SJ, Gardner WG, Shroff B, Tufekci E, Best AM. Influence of dental esthetics on social perceptions of adolescents judged by peers. Am J Orthod Dentofacial Orthop 2011;140:389–395.

17. Eitner S, Wichmann M, Schlegel KA, Kollmannsberger JE, Nickenig HJ. Oral health-related quality of life and implant therapy: An evaluation of preoperative, intermediate, and post-treatment assessments of patients and physicians. J Craniomaxillofac Surg 2012;40:20–23.

18. Glendor U. Epidemiology of traumatic dental injuries: A 12 year review of the literature. Dent Traumatol 2008;24:603–611.

19. Al-Sabbagh M. Implants in the esthetic zone. Dent Clin North Am 2006;50:391–407.

20. Xu H, Han X, Wang Y, et al. Effect of buccolingual inclinations of maxillary canines and premolars on perceived smile attractiveness. Am J Orthod Dentofacial Orthop 2015;147:182–189.

21. Tutak M, Smektała T, Schneider K, Gołe˛biewska E, Sporniak-Tutak K. Short dental implants in reduced alveolar bone height: A review of the literature. Med Sci Monit 2013;19:1037–1042.

22. Thoma DS, Haas R, Tutak M, Garcia A, Pietro Schincaglia G, Hämmerle CHF. Randomized controlled multicentre study comparing short dental implants (6 mm) versus longer dental implants (11-15 mm) in combination with sinus floor elevation procedures. Part 1: Demographics and patient-reported outcomes at 1 year of loading. J Clin Periodontol 2015;42:72–80.

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10

Implant Placement in Adolescents

Vincent J. Morgan | Paolo Perpetuini | Muneki Hirayama | Shadi Daher | Laura Murcko | Tan Min Seet | Lee Fuen Fuen | Rudolf Seemann | Joseph Leary

Implants have been successfully placed and restored in adults for decades, but controversy and confusion surround the concept of extending this treatment to adolescents.[1] The World Health Organization describes adolescents as people between 10 and 19 years of age.[1] The major source of concern in placing implants in young people stems from the skeletal and facial growth taking place in early adolescence: ages 10 to 14 for girls and 12 to 16 for boys.[1–4] Depending on the timing of implant placement, developmental changes may affect the position of the implant relative to the adjacent teeth and generate legitimate questions regarding prosthetic and aesthetic outcomes. On the other hand, if placement occurs later in adolescence, the effects of growth could be negligible.

The most common conditions that necessitate implants in adolescents are anodontia and trauma.[1,3] Before implant therapy became a treatment option, clinicians would typically provide a young patient with a removable or acid-etched prosthesis until growth and development was completed. Most young patients found this approach to be unsatisfactory for reasons of aesthetics and maintenance; there were also well-founded concerns about increased rates of caries and possible alveolar ridge resorption.[1] Parents shared these observations—combined with an acute awareness of their child’s psychologic needs—and often insisted on implant placement before growth and facial development were complete.[1,3] More implants are being placed in adolescents as it becomes clear that they benefit the patient socially, psychologically, and dentally (eg, ridge preservation and space retention).[1,4] The purpose of this chapter is not to refute the fact that dramatic physical changes occur in early adolescence and may affect long-term implant aesthetics, nor will we examine the details of facial growth and development; rather, we wish to show clinicians that implants can be confidently placed during early adolescence. The design of the Bicon implant is the key to managing potential prosthetic complications, and it enables both clinicians and their young patients to share in the rewards of implant therapy. This chapter focuses primarily on the implications of placing implants in adolescent patients and whether the clinical concerns unique to this population can be managed. The remainder of this chapter discusses the specific difficulties of placing implants in the changing adolescent oral environment and how implant design and restorative materials can affect success.

Concerns with Implants in Growing Patients

Many clinicians are still reluctant to place implants in adolescents because they have well-founded concerns based on prior experience using implant systems with screwretained implant elements. In these implant systems, the design of the abutment connection to the implant, otherwise known as its implant-abutment interface (IAI), is an inherently weak design; it exhibits micromovement and is often leaky and septic.[5–7] In such systems, a subcrestal implant placement is contraindicated, which severely limits the flexibility to place implants in this age group since they are still experiencing crestal bone growth. The difference between how implants and teeth react to the process of bone growth, and how one can cope with that difference, is the main cause of clinicians’ negative experiences.

In early adolescence, while the face and teeth are undergoing multidimensional changes, the interaction of the tooth’s periodontal ligament and surrounding bone maintains the normal relationship between the cementoenamel junction of the tooth and the crestal bone. Contrarily, the implant with its restoration has no ligament; it acts like an ankylosed tooth, anchored in place, possibly in a state of infraocclusion relative to the adjacent teeth.[1,2,8]

Although there have been anecdotal reports of success from clinicians using Bicon implants in young people, specific studies of the long-term effects of implant placement in adolescents are scarce.[3] To explore this subject and perhaps alleviate the expressed reservations of some clinicians, a retrospective study was undertaken at the Implant Dentistry Centre in Boston (Seemann R, unpublished data, 2017).The study investigated the results of using Bicon short implants with their locking-taper, plateau-root form design and subcrestal placement protocol in a group of 54 adolescents with an average age of 17 years. Among other things, the study analyzed the rate of success of implants placed and the frequency of active maintenance needed. The author reported an excellent cumulative survival rate of 94.6% throughout a 1-, 5-, and 10-year period of observation. The author’s findings included occasional prosthetic maintenance issues that were readily resolved by means of reinserting an abutment, carrying out chairside prosthetic adjustments, and occasionally providing a new restoration. The need for these services occurred primarily in patients younger than 16 years of age.

Some researchers have suggested that implants placed in patients younger than 16 years old may have to be removed; however, in no instance throughout this study did an implant have to be replaced.[1,9]

Bicon’s Unique Capabilities

What accounts for Bicon’s success in placing implants in adolescents when other systems have struggled? The key to Bicon’s successful adaptation to the changing conditions of adolescence is found in its subcrestal placement protocol, the macrogeometry of its design, and its broad array of restorative capabilities. The implant is intended to be positioned subcrestally in the alveolus; therefore, new bone growth (such as is seen at various stages of adolescence) simply changes the degree to which the implant is subcrestally positioned. Additionally, its locking-taper connection provides an expedient and reliable method for changing prosthetic restorations as a situation demands, and given the abutment’s 360 degrees of positioning capability, combined with the Integrated Abutment Crown (IAC), changing a restoration is a remarkably easy task. In many instances, chairside modifications can be made without removing an abutment by simply adding polyceramic composite material to the IAC restoration. This unique restorative capability mitigates many of the minor prosthetic complications associated with adolescent-related alveolar growth. Furthermore, Bicon’s IAI is impervious to bacterial infiltration and has no micromovement, so it can sit at a variety of bone depths without contributing to periodontal disorders or interfering with the needs of daily hygiene (see chapter 6).[6,7]

The advantages of the Bicon system are not limited to its prosthetic adaptability; in instances of congenitally missing teeth, there is often a lack of space to place an implant.[10] In the treatments that follow, some sites are so constricted vertically and horizontally that only a Bicon short and narrow implant could be placed. These unique features give clinicians who place Bicon implants a distinct advantage in the ability to offer replacements for missing teeth at an earlier age; they can do this secure in the knowledge that the implant design is flexible enough to respond to changing conditions relative to the implant’s position.

However, as reported in the Seemann study, occasional prosthetic maintenance issues did arise (mostly in patients younger than 16 years old). It is reasonable to expect that the earlier a patient is in the adolescent cycle, the more likely a prosthetic modification will be needed, and the more extensive it will be. If a prepubescent patient— younger than 10 years of age—presents for treatment, the clinician can anticipate that until they reach the end of puberty, their physical changes may be dramatic. During this period, the maxilla will be growing facially and inferiorly along the transverse, sagittal, and vertical axes. Although Bicon can provide a solution even under these conditions, the prudent clinician should weigh the benefits and draw- Fig 10-1 Preoperative radiograph of congenitally missing maxillary lateral incisors: right (a) , left (b) . (c) Postoperative radiograph of two 3.5 × 11.0–mm immediately loaded and stabilized implants. (d) Postoperative radiograph on the day of the IAC placements. (e to h) Postoperative clinical images and radiographs of the implants and IACs at 12-year follow-up.

backs of each individual’s situation and provide full disclosure regarding possible aesthetic complications.[8]

Bicon Implants in Adolescents

The following treatments of implant placement in adolescent patients should provide clinicians with an appreciation and understanding of the practicality of offering young patients the many benefits of implant-retained restorations. However, even though the Bicon system is extremely forgiving and can often provide solutions in the most challenging situations, this flexibility does not eliminate the clinician’s obligation to exercise sound judgment in placing implants in adolescents. The Bicon experience has been that there are rarely any issues when placing implants in patients older than 16 years; there can be complications with placement in younger patients, but to date these have been managed with ease.

Treatment 1: 16-year-old adolescent girl

The first patient, a 16-year-old adolescent girl, reflects one of the more common reasons for implant placements in adolescents: congenitally missing maxillary lateral incisors

(Figs 10-1a and 10-1b). The postplacement radiograph reveals the proximity of two 3.5 × 11.0–mm immediately loaded implants stabilized to the adjacent teeth (Fig 101c). (This was prior to the availability of the 3.0 × 6.0–mm implant.) Note that the narrow Bicon implant was able to be placed into the very small space available. Even in this minimal space, the implant’s sloping shoulder provides room for aesthetic and healthy papillae. The IACs were inserted (Fig 10-1d), but owing to an oversight, there was essentially no hemispheric base remaining in the IAC, which is not an ideal configuration for this restoration. Fortunately, there was no deleterious effect on the bone. The long-term clinical and radiographic results were apparent at the 12year mark, when the patient was 28 years old (Figs 10-1e to 10-1h).

Treatment 2: 15-year-old adolescent boy

In another example, a 15-year-old adolescent boy received a 4.5 × 6.0–mm implant in the site of his maxillary left lateral incisor (Figs 10-2a to 10-2c). Postoperative clinical and radiographic images, taken 8 years after implant placement, reveal a discrepancy in the length of the maxillary left lateral incisor IAC and his adjacent natural teeth (Figs 10-2d and 10-2e). Interestingly, the adjacent teeth appeared to be unaffected by the proximity of the implant, which was almost touching their roots. This is an example of the inherent prosthetic risk of having the adjacent teeth continue to erupt while the ankylosed implant remains stationary. This is more likely to occur when placing implants in adolescents younger than 16 years. Fig 10-2 (a) Clinical situation of a missing left lateral incisor in a 15-year-old adolescent boy. (b) Radiographic view after placement of a 4.5 × 6.0–mm implant. (c) Radiograph after IAC placement. (d and e) Eight-year postoperative clinical and radiographic images reveal a discrepancy in the length of the maxillary left lateral incisor IAC and the patient’s adjacent natural teeth. (f to m) The 8-year-old IAC is lengthened intraorally with a hybrid ceramic material. (f) The IAC surface is first roughened. (g and h) A bonding agent is brushed on, and a hybrid ceramic material is applied intraorally to lengthen the IAC. (i) The hybrid ceramic material is smoothed over to complete the lengthening of the IAC. (j to m) The surface of the lengthened IAC is roughened before being polished with a pink silicone wheel, gray silicone brush, and bristle brush. (n and o) Definitive views of the lengthened lateral incisor IAC at 8 and 10 years, respectively.

Figures 10-2f to 10-2m show the chairside correction of the length discrepancy of the 8-year-old IAC by adding additional hybrid ceramic material intraorally. Alternatively, the IAC could have been removed, and the lengthening could have been completed at a dental laboratory. The results shown in the image taken 10 years after implant placement are evidence that a clinician can confidently consider placing Bicon implants in an adolescent (Figs 10-2n and 10-2o). Fig 10-3 Preoperative radiograph (a) , postoperative radiograph (b) , and 5-year follow-up radiograph (c) and clinical appearance (d) of a congenitally missing maxillary right lateral incisor. Preoperative radiograph (e) , postoperative radiograph (f) , and 5-year follow-up radiograph (g) and clinical appearance (h) of a left first premolar. Preoperative radiograph (i) , postoperative radiograph (j) , and 5-year follow-up radiograph (k) and clinical appearance (l) of a right second premolar. (m) Facial image of the lateral incisor, first premolar, and second premolar IACs 5 years after placement.

Treatment 3: 19-year-old adolescent girl

The third patient was 19 years old when her three implants were placed. Clinical and radiographic images show preoperative, placement, and 5-year postplacement views of her lateral incisor and first and second premolars (Fig 10-3).

Once again, the advantage goes to the Bicon implant design; given the obvious space constraints, the placement of implants in the right lateral incisor and left first premolar positions would be problematic for any other implant system. Challenging sites such as these are ideal for the use of Bicon’s short and narrow implants. Fig 10-4 (a) Radiograph of a 15-year-old adolescent boy’s fractured central incisor. (b) Postplacement radiograph. (c) Clinical view following placement of the IAC. (d) Radiograph 4 months after placement of the IAC. (e) Clinical image after 7 years showing the effects of growth and development. (f) Clinical image of the sulcus. (g) Radiographic view after orthodontic treatment displaying the position of the implant. (h) Clinical image of impression post in preparation for a new IAC. (i) Clinical view of new IAC in situ 12 years after original placement. (j and k) Radiographic comparison of the original IAC after 12 years of use and new IAC in place.

Treatment 4: 15-year-old adolescent boy

The following 13-year sequence of images presents a patient who had an implant placed to replace his fractured maxillary right central incisor when he was 15 years old. The images show the fractured tooth, the implant, the IAC restoration in place, and the 4-month postplacement radiograph (Figs 10-4a to 10-4d). Seven years later, the effects of growth and development are evident (Fig 10-4e). At this point, the patient decided to have orthodontic treatment. The IAC was removed prior to treatment after having been in function for 7 years (Fig 10-4f).

Radiographic and clinical images show the final position of the implant and an impression post following completion of the orthodontic therapy (Figs 10-4g and 10-4h). No other implant system would be able to easily and effectively restore an implant in this position. Twelve years after the original implant placement, the new IAC was both functional and aesthetically pleasing (Figs 10-4i to 10-4k). The compensating pink nanoceramic material is hidden above his smile line, and most impressively, the implant had been successfully retained and restored twice, with bone levels that appear unchanged over the intervening 13 years. Fig 10-5 (a) Preoperative radiograph of a fractured maxillary right central incisor of an 8.5-year-old girl. (b) Panoramic radiograph following implant placement. (c) Clinical view 7 years later revealing length discrepancy of central incisors owing to continued eruption of natural teeth. (d) Ridge-lap IAC to correct the aesthetic complication following 7 years of alveolar growth and development. (e) Radiographic view of ridge-lap IAC. (f) Intraoral view of ridge-lap IAC. (g) The guide pin reveals the palatal position of implant after 7 years of alveolar growth. (h) Non-ridge-lap IAC. (i) Radiographic view. (j and k) Clinical views of non-ridge-lap IAC. (l) Clinical image of a new IAC after 9 years of function, when she was 17 years old.

Treatment 5: 8-year-old girl

The last treatment highlights the impressive flexibility of the Bicon implant when confronted with a challenging prosthetic complication. A prepubescent girl 8.5 years old presented with a fractured maxillary right central incisor (Fig 10-5a). A panoramic radiograph displays the implant placement and confirms her prepubescent status (Fig 105b). The length discrepancy revealed between the central incisors 7 years after the placement of the implant is the consequence of continued vertical eruption of her natural teeth as well as facial growth of the anterior maxilla along the sagittal plane (Fig 10-5c). At this time, when the patient was 15 years old, a ridge-lap IAC was initially offered as correction for the palatal positioning of the implant (Figs 105d to 10-5g). The ridge-lap IAC was not ideal, and a nonridge-lap IAC was fabricated (Fig 10-5h). The non-ridge-lap IAC was placed, and it provided an excellent and aesthetic solution (Figs 10-5i to 10-5l). Once again, the Bicon implant system offered a successful solution to a complex prosthetic challenge by simply replacing the restoration twice, once after 7 years and again after 8 years.

Conclusion

The introduction referred to a study of 54 adolescents with 84 implants in which the authors found a high rate of implant survival with excellent aesthetic results without the need to remove a single implant. There were some readily correctable prosthetic and maintenance issues occurring primarily in patients younger than 16 years of age; moreover, the treatments presented confirm the authors’ successful results.[3] The minimal risk of placing Bicon implants in adolescents is something to regard when considering the important service rendered to a psychologically vulnerable population of patients. The impressive prosthetic flexibility of the Bicon system with its locking-taper connection is an excellent option for patients who are still growing.

References

1. Shah RA, Mitra DK, Rodrigues SV, Pathare PN, Podar RS, Vijayakar HN. Implants in adolescents. J Indian Soc Periodontol 2013;17:546–548.

2. Op Heij DG, Opdebeeck H, van Steenberghe D, Quirynen M. Age as compromising factor for implant insertion. Periodontol 2000 2003;33:172–184.

3. Mishra SK, Chowdhary N, Chowdhary R. Dental implants in growing children. J Indian Soc Pedod Prev Dent 2013;31:3–9.

4. Wang WCW, Suinaga LT, Paranhos KS, Cho SC. Replacing missing teeth with dental implants in pubescent patients: A case report. Open J Pediatr 2015;5:207–212.

5. Berberi A, Tehini G, Rifai K, et al. In vitro evaluation of leakage at implant-abutment connection of three implant systems having the same prosthetic interface using rhodamine B. Int J Dent 2014;2014:351263–351267.

6. Zipprich H, Weigl P, Lauer HC. Micromovements at the implant-abutment interface: Measurement, causes, and consequences [in German]. Implantolgie 2007;15:31–45.

7. Dibart S, Warbington M, Su MF, Skobe Z. In vitro evaluation of the implant-abutment bacterial seal: The locking taper system. Int J Oral Maxillofac Implants 2005;20:732–737.

8. Enlow DH. Facial Growth, ed 2. Philadelphia: W B Saunders, 1990.

9. Oesterle LJ, Cronin RJ, Ranly DM. Maxillary implants and the growing patient. Int J Oral Maxillofac Implants 1993;8:377–387.

10. Nirola A, Bhardwaj SJ, Wangoo A, Chugh AS. Treating congenitally missing teeth with an interdisciplinary approach. J Indian Soc Periodontol 2013;17:793–795.

11

Restorative Techniques

Paolo Perpetuini | Kristina Pisarik | Vincent J. Morgan | Estevam Bonfante | Katherine Morgan | Drauseo Speratti | Muneki Hirayama | Laura Murcko | Stefano Carelli | David M. Hallowes

The surgical placement of implants represents only a portion of the total dental implant process; the restorative materials and techniques offered by an implant system are equally important. Moreover, it is necessary to keep in mind that a patient’s desire is to have a missing tooth or teeth replaced, not to have one or more implants. Therefore, the osseointegration of implants is necessary, but only as a means to an end; for the patient, what is important is the replacement of their missing teeth. If an implant is osseointegrated but it is not aesthetically pleasing and functional in the eyes of the patient, then it has still failed—not in terms of stability within the bone but by disappointing the patient.

The Bicon dental implant system provides the opportunity to use restorative materials and techniques that offer unmatched clinical capabilities, the most apparent being the properties intrinsic to the locking-taper implant-abutment interface (IAI). A locking-taper IAI allows for 360 degrees of abutment positioning, a design aspect that provides patients with exceptionally aesthetic and functional restorations—even in the most challenging situations—and permits the use of revolutionary prosthetics such as Integrated Abutment Crowns (IACs) and TRINIA telescopic restorations. The Bicon IAI frees clinicians from the use of screws, not only providing financial savings but also significantly reducing the total restorative time and number of patient visits. Furthermore, the locking-taper IAI creates a bacterial seal, which prevents the accumulation of deleterious bacteria in the implant well and prevents micromovement of the abutment within the implant (see chapter 6).

In addition to the locking-taper IAI, there are other aspects of the Bicon system that make it unique: a sloping shoulder, which provides room and bony support for aesthetic interdental papillae; a hemispheric abutment base, which stimulates crestal bone growth; the use of novel composite materials; cement- When technicians are not burdened by the need to provide an access screw hole in an implant restoration, they can create an aesthetic crown with greater ease. Although Bicon abutments may be restored with screw retention by using Fixed-Detachable Abutments and with any restorative material, the use of polyceramic or nanoceramic materials to create IAC restorations is recommended.[3] These materials are preferred because they are less abrasive and can be easily modified by either adding or reducing material from their surface throughout their clinical life—a characteristic appreciated by any experienced practitioner.

Fig 11-1 (a) Image of an IAC. (b) Illustration of Universal Abutments with retentive telescopic copings.

Integrated Abutment Crown

less and screwless restorations (IAC); Universal Abutments with retentive copings; and TRINIA, a versatile, metal-free, fiber-reinforced computer-aided design/computer-assisted manufacturing (CAD/CAM) material that facilitates the fabrication of telescopic restorations.

Since its inception, Bicon has offered a variety of creative abutments, which are described in chapter 2. The most recent addition is the Universal Abutment, which possesses a number of corresponding prosthetic components, including both retentive and nonretentive milled copings for telescopic restorations. The geometry of the abutment is digitally friendly in that it can be accurately scanned, negating the need for manual refinements when it is viewed virtually. Additionally, its 4.0-mm prosthetic post height is sufficient to support both conventional and digital restorations, while providing maximal space for aesthetic materials, particularly when an implant’s trajectory is less than ideal.

The hemispheric base found on Bicon abutments provides the opportunity to create an emergence profile similar to that of a natural tooth. It also produces a slight natural displacement of the gingival margin, which affords the technician the opportunity to create exceptional cervical aesthetics and function. This emergence profile lends the restoration a pleasing, natural appearance, and the soft tissues thrive in the presence of a normal gingival architecture.

An IAC is fabricated by successively bonding layers of a polyceramic or nanoceramic resin material to an abutment to create a single unit integrating the crown and abutment. It would be classified as an abutment-supported porcelain-ceramic crown by the American Dental Association’s definitions (see chapter 3). An IAC is only possible in a dental implant system with a locking-taper IAI because screw-in abutments require a screw to fasten an abutment to the implant—a characteristic that imposes severe limitations upon their restorative flexibility.

Extraneous cement, which is a byproduct of attaching conventional crowns to screw-in abutments, can cause gingival irritation and sometimes lead to peri-implantitis. Because the crown of an IAC is composed of successive layers of material chemically bonded directly to the abutment and is not intraorally cemented, all of the potential deleterious effects of extraneous cement are eliminated, and with them, the potential for injuries to the soft and hard tissues.[1,2]

Because they are composed of a composite resin, IACs allow for easy chairside modifications, a property that saves time and money by removing the involvement of a laboratory for every minor change. Examples of chairside modifications include functionally derived closure of open interproximal contacts, adjustment of hyper- or hypo-occlusal contacts, covering of metal margins, bonding of new pontic restorations, and changes of color and contours of existing restorations for aesthetic or functional reasons.

Restorative Materials

Basic Restorative Techniques

The Bicon implant system is compatible with all known restorative materials, including gold, porcelain-fused-to-metal (PFM), metal-ceramic, and all-ceramic crowns; however, there are two restorations that have proven to be highly successful and are only possible in a system with 360 degrees of abutment positioning: IACs and TRINIA telescopic restorations with retentive copings.[1,2] These unique prosthetic restorations preclude the use of screws as well as the use of cement, thereby removing the damage that any potential extraneous cement may precipitate[1,2] (Fig 11-1).

The easiest way for a restoring dentist to understand and restore a Bicon abutment is to consider a seated abutment as they would a post and core restoration or a prepared crown preparation on a natural tooth, and simply take a conventional impression of it. As an alternative to taking a direct conventional impression of the abutment, an implant- or abutment-level transfer impression may be made. Direct digital scanning of abutments or indirect scanning of an implant’s relative position can be achieved using Scanning Posts. Detailed instructions on the different impression options can be found at www.bicon.com. Fig 11-2 (a) A 5-mm Sulcus Former on a threaded instrument Adapter rotating on a guide pin to remove any tissue over the implant. (b) The three color-coded guide pins: violet, 2.0 mm; blue, 2.5 mm; and green, 3.0 mm. (c) A yellow thermoplastic custom-made seating jig in a Crown-Seating Tip was used to seat a definitive mandibular incisor IAC on the long axis of the implant. (d) If an adjacent tooth or an implant interferes with the full rotation of a Sulcus Former, one of the Sulcus Former’s blades can be removed to avoid any interference. (e) Radiograph of an abutment in close proximity to its adjacent distal tooth. The sulcus was formed with a single-blade Sulcus Former.

Sulcus Formers, guide pins, a Crown-Alignment Device, and Crown-Seating Tips are restorative instruments specific to the Bicon implant system (Figs 11-2a to 11-2c). Briefly, the Sulcus Former is rotated around a guide pin that has been seated in an implant well. As the Sulcus Former is rotated, it forms a sulcus by removing both soft and hard tissue over the implant; this is done to accommodate the hemispheric base of the intended abutment, an action similar in effect to countersinking. Sulcus forming is an essential step to ensure the complete seating of an abutment in an implant well and the resulting activation of the lockingtaper connection. It is possible to avoid cutting into a contiguous structure by removing one of the two blades of the Sulcus Former and subsequently rotating it less than 360 degrees (Figs 11-2d and 11-2e).

The Crown-Alignment Device is used to fabricate a custom thermoplastic seating jig. The custom-made jig is then seated in a Crown-Seating Tip and used to tap an abutment or an IAC into an implant well. This device is essential for seating angled abutments because it helps to ensure that the abutment seating forces are directed along the long axis of both the abutment shaft and the implant well.

The seating jig is fabricated by first seating the shaft of the restoration’s abutment into the Crown-Alignment Device (Fig 11-3a). Then, a thermoplastic resin is softened in a water bath (180ºF/82.2ºC) and inserted into the Crown-Seating Tip (Fig 11-3b). While the thermoplastic resin is still hot enough to be malleable, the alignment device is closed, allowing the resin material to capture an impression of approximately the incisal third of the crown (care should be taken not to cover the interproximal sides of the crown) (Fig 11-3c). The cooled jig is removed from the alignment device and placed in cold water. Methyl methacrylate may also be used, though a separating medium must be applied to the restoration to prevent bonding with the methyl methacrylate.

The Crown-Seating Tip, with the custom-made jig in place, is then screwed into a straight handle and used to definitively seat the already tentatively seated abutment or IAC by applying a few gentle taps to the end of the straight handle to activate the locking taper (Fig 11-3d).

Restorative Crown Techniques

The remainder of this chapter presents clinical examples demonstrating the versatility of Bicon’s techniques and its range of treatment options. Additional treatments are also presented, illustrating how seemingly difficult treatments can be accomplished with ease because of the unsurpassed clinical capabilities and design of the Bicon implant and abutments. Fig 11-3 (a) Crown-Alignment Device for making custom seating jigs. (b) IAC and thermoplastic resin custom-made seating jig in a Crown-Seating Tip. (c) A custom-made Crown-Seating Jig prior to and after being screwed into a straight threaded handle. (d) A Crown-Seating Jig on a straight handle seating a definitive maxillary incisor IAC. Fig 11-4 (a) Restoration and custom-soldered abutment with blue 2.5-mm guide pin demonstrating the extreme seating angle for the poorly positioned implant. (b) Right profile view of the blue 2.5-mm guide pin inserted into the poorly positioned implant. (c) Incisal view of the well of the implant. (d) Left profile view of the custom abutment being placed into the implant. (e) Left profile view of the definitive seating by tapping the dimple in the abutment with a violet 2.0-mm seating tip to facilitate directing the seating forces along the long axis of the implant. (f) Facial view of the seated custom abutment. (g) Facial view of the restored lateral incisor implant with a PFM crown. (h) Radiograph of the restored poorly positioned implant.

Restoration of a poorly positioned maxillary incisor implant

This procedure demonstrates the versatility of the Bicon system with its ability to restore a poorly positioned maxillary anterior implant. In this case, the trajectory of the implant was at a roughly 45-degree angle relative to the long axis of the adjacent teeth (Fig 11-4).

Four crowns on Universal Abutments with three different materials

The three successive examples demonstrate the restoration of a single patient’s four implants using three different materials: PFM, zirconia, and a modified polyceramic CAD/ CAM material (Figs 11-5 to 11-7). Fig 11-5 This procedure presents the fabrication of four PFM crowns and their placement onto Universal Abutments. (a) Stone was poured into a full-arch implant-level transfer impression with four implant analogs. (b) Four unmodified low-profile Universal Abutments in stone model. (c) Labial view of wax-up. (d) Sprued four units with three different waxes. Red is the weakest in memory and facilitates removal from the abutment. Green is the hardest and provides strength. Violet is a stable wax and provides marginal integrity. The 3.0-mm cervical sprue is attached to a 5.0-mm horizontal bar, which is attached to two 4.0-mm vertical struts. Four 0.8-mm channels provide venting. (e) Four chrome-cobalt castings with one in a Universal Abutment, which was seated without any modification. (f) Four finished and airborne particle–abraded chrome-cobalt castings on Universal Abutments. (g) Opaqued castings. (h) Opaque dentin was applied with shade A4 for the cervical third and D3 for the incisal third.

As mentioned in chapter 9, the restoration of anterior implants plays a significant role in a patient’s well-being because of the major effect that their visible teeth and gingiva have upon their smile. Therefore, the prosthetic techniques for anterior implants must be carefully chosen, not just for the successful placement of functional and aesthetic restorations, but also for the ease of maintaining aesthetic restorations over the long term. The use of IACs offers clinicians unmatched clinical capabilities and avoids the maintenance issues inherent with other techniques and materials. The treatments demonstrated in the following presentations provide clinicians with an understanding of the unmatched clinical capabilities of the Bicon implant and abutments. (Figs 11-8 to 11-13). Fig 11-5 (cont) (i) Cervical shade A4 was applied to root area, dentin shade A4 was applied to the middle third, and dentin shade D3 was applied to the incisal third; layers of several shades of translucent porcelain were applied to areas above the interface with dentin in the incisal third. (j) Red pencil markings indicated the intended height of contour consistent with that of the adjacent canines. (k) Translucent and neutral porcelain were applied to finalize the contour between the root and crown area. (l) Red pencil markings depicted the height of surface contours, which influenced the reflection of light and the anatomical compatibility with mandibular incisors. (m) Ink from articulating paper revealed the surface texture. (n) Glazed restorations. (o) Initial placement of PFM crowns. (p) Clinical view of placed PFM crowns. Fig 11-6 This procedure demonstrates the brief process of fabricating four zirconia maxillary incisors and placing them onto Universal Abutments. (a) Opaqued castings for zirconia crowns. (b) Glazed zirconia restorations. (c) Initial placement of four layered zirconia crowns on Universal Abutments.

Polyceramic CAD/CAM block

Fig 11-7 This procedure demonstrates the CAD/CAM process of modifying polyceramic crowns on four Universal Abutments. (a) Sprayed wax-up prior to digital scanning. (b) Sprayed Universal Abutments prior to digital scanning. (c) Digital image of abutments and articulated models. (d) Digital image of four waxed-up incisors. (e) Shofu blocks prior to being milled. (f) Milled Shofu blocks. (g) Milled incisors were stained prior to application of several layers of a polyceramic composite material. (h) Dentin, enamel, and incisal material were applied. (i) The oxygen barrier was applied prior to final light curing. (j) Ink from articulating paper revealed the surface texture. (k) Four manually polished maxillary incisor restorations. (l) Initial placement of four CAD/CAM polyceramic composite crowns on Universal Abutments.

Single mandibular IAC

Fig 11-8 This procedure demonstrates how to fabricate a single mandibular IAC. (a) Implant-level transfer impression was made with red 2.0-mm Impression Post and Sleeve. (b) Full-arch implant-level transfer impression with captured 2.0-mm red acrylic sleeve within it. (c) Gingival contour was marked on the abutment to facilitate preparation of minimally subgingival facial margin and crestal or supragingival margin in nonaesthetic areas. (d) Abutment with subgingival margin was prepared with no sharp angles. (e) Abutment shaft was inserted into wax for its protection during airborne-particle abrasion of the prosthetic post with 250-μm sand. (f) Airborne particle–abraded abutment was put in abutment prep holder for the application of metal link primer and preopaque paste. (g) Appropriate shade of opaque was applied to the abutment. (h) Opaque dentin paste was applied with two shades to establish the final shape and shade. (i) Dentin paste was applied to opaque dentin with the same stratification layering as opaque dentin. (j) Blue and gray incisal pastes were blended prior to being applied to the dentin paste. (k) Characterization was initiated with the selective application of incisal paste to establish a contrast with areas of exposed dentin paste at the incisal third. Cervical stratification was achieved by applying clear dentin paste at the cervical third. (l) A variety of internal stains can be placed prior to the application of neutral pastes. (m) Internal stains established apparent craze lines. (n) Neutral paste covered staining liquid in a sandwich technique. (o) Stratification was completed, giving the appearance of a three-dimensionally shorter anatomical crown and root. —_ Fig 11-8 (cont) (p) Final interproximal contours were established with application of enamel paste and covering with an oxygen barrier before final light curing. (q) A silicone rubber wheel was used to finish the margin or interface between titanium abutments and polyceramic material. (r) A pencil outline indicated the height of surface contours, articulating paper ink delineated surface contours, and incisal contacts were confirmed. (s) Incisal view of rotated teeth. (t) Restoration was polished with a pink silicone wheel. (u) Polishing continued with a silicone brush rotating at 8,000 rpm with liquid soap to avoid burning the surface. (v) A bristle brush with diamond paste was used to continue the polishing. (w) A cloth wheel was used to finish the surface polishing. (x) Finished IAC on stone model. (y) Yellow thermoplastic orientation jig on model. (z) Cementless and screwless IAC. (aa) Initial placement of IAC. (bb) Five-year postplacement image revealing not only an anatomically aesthetic restoration but also anatomically aesthetic and healthy gingival tissues. (cc) Five-year postplacement radiograph.

Single maxillary IAC

Fig 11-9 This procedure shows the process of fabricating a single maxillary IAC and its postplacement clinical appearance. (a) A green 3-mm impression post was inserted. (b) An implant-level transfer impression was made with a green 3-mm acrylic sleeve on the impression post. (c) Green 3-mm acrylic sleeve within full-arch impression. (d) Pink Softissue Moulage (Kerr) was injected around the green impression post and orifice of the implant analog for fabrication of a soft tissue model. (e) The abutment was marked for modification. (f) The margin was prepared on the abutment. (g) The prepared abutment was placed in the soft tissue model to confirm subgingival margin placement. (h) The prepared abutment was inserted into wax to protect its shaft during airborne-particle abrasion of its prosthetic post, and then it was inserted into the brass implant analog for application of opaque primer. (i) Opaque paste was applied with a brush. (j) Opaque paste was light cured for 3 minutes. (k) Opaque dentin paste was applied with a spatula. (l) Finished IAC on stone model after application of opaque dentin, dentin, enamel, and incisal pastes. (m) Yellow thermoplastic seating jig was formed in a Crown-Alignment Device. (n) The locking-taper shaft was cleaned with alcohol. (o) Insertion site. (p) The IAC was definitively seated with the seating jig, which directed the seating forces along the long axis of the implant well. (q) View of IAC immediately after being placed, revealing an ideally aesthetic restoration and gingival tissues. (r) Postplacement radiograph.

Four individual maxillary IACs

Fig 11-10 This procedure exemplifies the laboratory’s process of fabricating four individual IACs and clinical chairside repair and polishing of the IACs at a 5-year follow-up visit. (a) Four blue 2.5-mm implant-level transfer impression posts. (b) A full-arch implant-level transfer impression was made with four blue acrylic sleeves. The implant analogs were attached to their corresponding impression posts within the impression, and a separator medium was applied. (c) Pink Softissue Moulage was injected around the impression posts and orifices of the implant analogs. A full-arch impression was boxed with red wax, and then the stone model was poured. (d) Because indirect polyceramic composite materials are stronger in bulk, abutments with only 4.0 mm of prosthetic post height are ideal. (e) The abutment shafts were put in red wax for protection and then airborne-particle abraded with 250-μm sand, and opaque was applied. (f) A 2-mm-thick layer of shade A4 opaque dentin was applied to the abutments, and they were light cured for 3 minutes. Then, a second 2-mm incremental layer of shade A1 opaque dentin was applied, and the abutments were light cured again. (g) A4 dentin was applied to the cervical half and A1 dentin to the incisal half and minimally over the incisal third of the cervical half. The IACs were then contoured with enamel and neutral pastes. (h) The IACs were covered with an oxygen barrier prior to their final 3 minutes of light curing. (i) Red articulating paper ink delineated the surface contours. (j) Four IACs on the day of placement. (k) Five-year postplacement views of right incisors with original polish and repolished left incisors. Note the gingival health, aesthetics, and chipped right lateral incisor. —> Fig 11-10 (cont) (l) The surface was roughened with a flame finishing bur to repair the chipped surface. (m) Alcohol was used to clean the surface, and then modeling liquid was applied and light cured. (n) White incisal paste was applied with a spatula, and then a blue oxygen barrier was applied, and the surface was light cured again. (o to r) The IAC was polished with a silicone cylinder bur (o) , a Upofix silicone wheel (Dentsply Austenal) and water (p) , a bristle brush and diamond paste (q) , and a cotton wheel (r) . (s) Note the difference between the repolished right incisors and the original 5-year-old polish of the left incisors. (t) Patient’s smile after the intraoral polishing of 5-year-old IACs. (u) Five-year postplacement radiograph revealing the height of the prosthesis posts supporting the polyceramic indirect composite material.

Full arch of individual IACs

Fig 11-11 This procedure demonstrates the fabrication of a full arch of individual IACs. Although one implant per tooth is not necessary, as evidenced by the treatments with full-arch TRINIA telescopic restorations that follow, it can be a desirable treatment if it is financially convenient for the patient. (a) A full-arch implant-level transfer impression was made with 10 acrylic sleeves captured within. (b) Dentin paste and then enamel paste were applied to the opaqued abutments. (c) First premolar cantilever without metal support was evidence of the fact that polyceramic composite materials have clinical and mechanical properties unavailable in many other dental restorative materials. (d) Confirmation of the fact that the surface contours successfully reflect and refract light in an aesthetic manner. Gingival stratification and contours delineate appropriate anatomical features to minimize the appearance of an excessively long restoration. (e) Yellow thermoplastic orientation jig on stone model. (f) Occlusal view. (g) Left profile view. (h) Postplacement radiograph.

Intraoral postplacement covering of metallic margin and shade modification

Fig 11-12 This procedure demonstrates how to cover a metal margin and modify an IAC’s shade intraorally for an excellent aesthetic outcome. (a) Aesthetically unacceptable exposed metal margin. (b) Image of 2.5-mm implant well and soft tissue sulcus after removal of IAC. (c) IAC crown in blue 2.5 implant analog within stone model. (d) IAC in Prep Holder after reduction of facial titanium. (e) The IAC shaft was embedded in wax, and the modified surface was airborne-particle abraded with 250-μm sand. Then modeling liquid was applied with a brush, and the IAC was light cured. Preopaque paste and opaque were applied with a brush and the IAC was light cured again. (f) The facial surface of the IAC was roughened with a silicone silver bur. (g and h) Modeling liquid, opaque dentin, and cervical translucency were each applied and light cured. (i) The surface was finished with a gray silicone wheel before being polished with a pink silicone cylinder bur, Upofix silicone brush with water, and a cotton wheel and polishing paste. (j) Image 4 months after cervical modification to cover metal appearance. (k) For shade modification, the cervical area was roughened with a flame carbide finishing bur, then modeling liquid and neutral paste were applied and light cured. (l) The surface was finished with a flame carbide finishing bur and polished with a pink silicone wheel and then a silicone Upofix wheel and water. (m) Clinical image after modification.

Two zirconia CAD/CAM copings for single restoration

Fig 11-13 This restoration confirms the fact that Bicon abutments can conform to the individual preferences of most clinicians by using two CAD/CAM zirconia copings to restore a single maxillary central incisor implant. (a) Unmodified Universal Abutment in soft tissue model. (b) A wax cast of the zirconia coping was attached to an unmodified Universal Abutment. (c) The presintered customized zirconia coping was finished with a silicone bur. (d) The sintered customized zirconia coping on the abutment in the model. (e) The zirconia coping was milled and then removed from the disc. (f) The sintered zirconia coping on the model. (g) Dentin, porcelain, and stratification with mamelons on zirconia contour. (h) Incisal porcelain layering. (i) The first bisque bake revealed the shades used. (j) Dentin and incisal applications were applied for final contour, the second bisque bake confirmed interproximal contacts, and the restoration’s anatomy was finalized. The restoration was glazed and finished. (k) Clinical image immediately upon placement. (l) Postplacement radiograph.

Implant retained denture on a Dolder bar

Fig 11-14 (a) Angled Fixed-Detachable Abutments were placed into the implant well to assess the possibility of achieving parallel alignment of all three abutments. (b) Different angled abutments were rotated to easily achieve parallel alignment. (c) Angled Fixed-Detachable Abutments were definitively seated. (d) The Hex Coping Screws were removed, and the three Fixed-Detachable Abutments were in parallel alignment. (e) Radiograph revealed parallel alignment of abutments even though implants were not parallel. (f and g) A metal impression coping was inserted onto each abutment, and an impression transfer coping was fastened. (h) The three transfer copings were splinted together with red resin, and a full-arch transfer impression was taken. (i) Transfer copings within the full-arch impression were unfastened, and brass abutment analogs were fastened to the transfer copings within the impression. (j) A stone model was poured around the abutment analogs to fabricate a master model. (k) Occlusal registration was recorded. (l) The arrangement of teeth was digitally scanned, and a digital image was taken of the three abutments and the proposed Dolder bar. (m) The Dolder bar was digitally designed prior to milling. —— ,

Removable Restorations

Implant-retained and implant-supported dentures are fully compatible with the Bicon system. Implant-retained dentures can be attached to specialized o-ring or locator abutments, and implant-supported dentures can be attached using milled, telescopic sleeve abutments. The following two treatments, shown in Figs 11-14 and 11-15, demonstrate the laboratory steps that are involved in fabricating mandibular removable prostheses: one with a milled Dolder bar on three Fixed-Detachable Abutments, and the other with a cast chrome-cobalt bar and stabilizing post and clips on four Fixed-Detachable Abutments. Fig 11-14 (cont) (n) The milled Dolder bar was affixed to three Fixed-Detachable Abutments on the model. (o) Pink wax was applied around the Dolder bar to block out undercuts. (p) An impression was taken for model duplication, and the acrylic denture was bonded with resin to the Dolder bar clips on the model. (q) The denture with Dolder bar attached with three clips was removed from the model. (r) The milled bar was fastened to abutment analogs prior to confirming appropriate seating of the denture with bonded clips on the model. (s) The denture was attached to the Dolder bar on the stone model. (t) Intaglio of denture with Dolder bar clips. (u) Denture was placed onto the Dolder bar. (v) Radiograph of three parallel abutments on three nonparallel implants 22 years after placement.

Implant retained denture on cast chrome-cobalt bar

Fig 11-15 (a) Four Fixed-Detachable Abutments were positioned parallel to one another. (b) Wax arrangement of teeth on chrome-cobalt bar. (c) Primary cast chromecobalt bar was fastened to four Fixed-Detachable Abutments. (d) Finished denture on model. (e) Intaglio of secondary cast chrome-cobalt bar in denture. (f) Female attachment groove was formed by spark erosion. (g) View of bar with open clips. (h) View of secondary bar with closed male clip.

TRINIA prosthetic techniques

TRINIA is a fully biocompatible metal-free fiber-reinforced resin CAD/CAM material, also known as a multiphasic material . It is composed of approximately 60% filaments or strands of fiberglass and 40% resin, and it has been used as a restorative dental material since 2010. These multiphasic materials are imbued with the improved properties of their constituent phases. Also known as hybrids , the rationale behind multiphasic materials is to combine two or more materials in an attempt to get the best attributes of both.

TRINIA has a relatively high flexural strength and a flexural modulus similar to that of dentin, with the added benefit of being lightweight. The flexural modulus of TRINIA is 18.8 GPa; dentin and titanium, in comparison, have flexural moduli of 12 to 14 GPa and 102 to 118 GPa, respectively. Possessing a similar flexural modulus to dentin means that TRINIA shares its elastic properties.

When bonded to enamel or dentin, the bond strength of TRINIA is sufficient to withstand the forces present in the mouth. In tests where TRINIA was bonded using 3M RelyX Unicem 2 Automix, the bonds were broken against the enamel or dentin side but stayed intact on the TRINIA side. TRINIA may be used in conjunction with polyceramic restorative material with similar sheer bond strength. Even after thermocycling, in which TRINIA was exposed to a high

Fig 11-16 White and pink TRINIA discs and block.

range of temperatures thousands of times, the bond stayed intact and at a sufficient strength.

TRINIA is available in either pink- or cream-colored 98-mm discs or 40.0- and 55.0-mm blocks (Fig 11-16). It can be milled on most wet or dry milling machines using nanodiamond or conventional dental burs, and it readily accepts a variety of bonding materials. TRINIA can be used to fashion copings, substructures, or frameworks, and it can also be used to fabricate either definitive or provisional prostheses for natural teeth or for any implant system. Because TRINIA does not require curing or sintering, its processing represents a more cost-effective option compared with other materials. The following laboratory cases demonstrate the use of TRINIA in a series of challenging situations (Figs 11-17 to 11-20).

Four-unit TRINIA fixed partial denture

Fig 11-17 This case shows the milling and polishing of a four-unit TRINIA fixed partial denture prior to placement. (a) After the gingival contours were marked on the abutments, the abutments were checked for parallelism. (b) Milled abutments were digitally scanned. (c) The fiber-reinforced resin TRINIA was milled for a four-unit anatomical framework. (d) TRINIA framework was modified with a silicone bur. (e) The appropriateness of the TRINIA framework was confirmed. (f) A and B primer were applied, then opaque dentin was applied, and the framework was light cured for 3 minutes before final sealing paste was applied with a brush. (g) The prosthesis was adjusted on the model for incisal contacts. (h) Surface contours were delineated with articulating paper ink. (i) Polishing was initiated with a pink silicone cylinder bur and then continued with a pink silicone wheel, a silicone brush rotating at 8,000 rpm with liquid soap to avoid burning the surface, a bristle brush and diamond paste, and finally a cloth wheel. (j) Facial view of finished four-unit TRINIA prosthesis. (k) Palatal view of finished four-unit TRINIA prosthesis. (l) The occlusion was confirmed with articulation paper. (m) Reflected palatal view of blue ink marking the incisal contacts. (n) Postplacement radiograph of the four-unit TRINIA prosthesis. Fig 11-18 This case presents the process of fabricating a mandibular full-arch screw-retained TRINIA prosthesis. (a) Four blue impression posts and acrylic sleeves were placed for the making of a full-arch implant-level transfer impression. (b) A soft tissue model was fabricated with four straight or zero-degree Fixed-Detachable Abutments. (c) Wax teeth arrangement was placed on a light-cured resin bar. (d) Nonanatomical milled TRINIA bar was fastened to four Fixed-Detachable Abutments, and screw access holes were covered with red wax. (e) A silicone mask was used to confirm the appropriateness of attached composite denture teeth seated on the TRINIA bar. (f) Pink denture resin was poured into the silicone mask and around the TRINIA bar to bond composite denture teeth to the bar and form flanges. (g) The silicone mask was removed for finishing and polishing of the bar, and the screw-retained prosthesis was removed from the cast. (h) Occlusal view of screw-retained TRINIA prosthesis. (i) After inserting the screw-retained prosthesis and fastening it to four Fixed-Detachable Abutments intraorally, the gutta-percha over the screws was covered with flowable composite to seal the screw access holes. (j) Postplacement clinical image of occlusal surface of definitive prosthesis. Fig 11-19 This case shows the intraoral relining of a maxillary TRINIA bore to rectify a vertically ill-fitting bore around an abutment. (a) Four parallel abutments. (b) The TRINIA bar was cleaned with alcohol, and modeling liquid was applied to the bore of the TRINIA prosthesis. (c) The modeling liquid was light cured. (d) The white composite paste was kneaded before being applied to the bore of the TRINIA prosthesis. (e) Petroleum jelly was applied to the milled abutment prior to placement of the prosthesis into the implant, and the white paste was light cured in the bore of the seated prosthesis. (f) The angled abutment was removed after the initial relining and intraoral light curing of the abutment bore. (g) Additional polyceramic material was applied to the prosthesis around the abutment margin. (h) White polyceramic paste was added to seal the margin of the abutment prior to being light cured for 3 minutes. (i) Once the abutment perfectly adapted to the bore of the TRINIA prosthesis, it was removed. (j) The bore of the prosthesis was relined and reshaped to achieve ideal adaptation to the milled abutment, and it was then used to reseat the abutment into the well of the implant.

Intraoral reline of a maxillary full-arch TRINIA restoration

Fig 11-20 This case demonstrates the intraoral relining of a maxillary full-arch TRINIA restoration. (a) The TRINIA surface was roughened with a silicone cylinder bur. After alcohol cleaning, modeling liquid was applied and light cured. (b) Pink polyceramic pastes were blended to achieve the appropriate shade. (c) Pink polyceramic paste was applied to the intaglio of the prosthesis. (d) The prosthesis was seated onto abutments to adapt polyceramic paste to the alveolar ridge. (e) Excess paste was removed as the prosthesis was fully seated, and paste was adapted to the ridge with a spatula and brush. (f) Intaglio view with reflection of polished and relined prosthesis. (g) Postplacement intraoral view of polished and relined TRINIA prosthesis.

Telescopic TRINIA restorations

Initially, when the first fabricated fixed TRINIA partial denture restorations were introduced, they were designed to be intraorally cemented prostheses; however, because of irretrievability, hygiene, and extraneous cement issues, telescopic restorations (using various materials and techniques for custom telescopic copings) were chosen as the preferred method. Fortunately, Universal Abutments with their milled, standardized titanium telescopic copings have provided clinicians and technicians with a more efficient and cost-effective way of fabricating TRINIA telescopic prostheses (Fig 11-21).

The prefabricated milled copings are available in two colors and two sizes. Silver copings are nonretentive, and purple copings are retentive in conjunction with other purple copings; they are not retentive on an individual abutment. Only their cervical 2.0 mm of height contribute to their retentiveness; therefore, their height may be reduced for vertical clearance, if necessary, without reducing their reten tiveness. All copings are available in two sizes: Copings with a numeric marking are specific for low-profile Universal Abutments, and copings without a numeric marking are for either standard- or tall-profile Universal Abutments (Fig 11-22).

Milled telescopic copings almost always eliminate the need for custom copings, provide for a precise marginal adaptation to an abutment, eliminate the need for intraoral cementation to an abutment, and facilitate gross adjustments of the TRINIA prosthesis. The intraoral resin cementation of the coping (rather than the abutment) to the

Fig 11-21 Two purple retentive telescopic copings and one silver nonretentive telescopic coping.

Fig 11-22 Four standard profile telescopic copings (three retentive, one nonretentive) on Universal Abutments on a soft tissue stone model. Fig 11-24 The top of a Universal Abutment is modified to facilitate the intraoral placement of the prosthesis.

Fig 11-23 (a) Light-cured resin is applied to four telescopic copings on a soft tissue model. (b) A verification jig with flowable light-cured resin over telescopic copings on a stone model. (c) A seating jig and a verification jig with telescopic copings cemented in their bores. (d) A digitally printed verification jig with telescopic copings cemented in its bores.

Fig 11-25 The divergence of Universal Abutments is measured with a Girod-Tast device.

TRINIA prosthesis readily fills any void between the milled coping and the TRINIA prosthesis, while providing a precise marginal adaptation of the coping to the abutment.

Additionally, the coping’s closed end may be modified for occlusal or facial clearance without compromising its retentive function. Unlike traditional telescopic copings, retentive copings are not retentive with a singular abutment; rather, they gain their retentive function from the 2 to 3 degrees of divergence between or among the restoration’s Universal Abutments. The path of placement and retentive efficacy of the definitive TRINIA prosthesis, with a combination of abutments and copings, can be evaluated in the laboratory by attaching the copings to a light-cured resin verification jig. The verification jig simulates the definitive prosthesis to confirm both its path of placement and retentiveness prior to the copings being cemented intraorally to the definitive TRINIA prosthesis (Fig 11-23). If necessary, the retentiveness of the prosthesis can be modified by changing the combination of the copings, slightly rotating one or more abutments, or replacing two straight abutments with angled abutments to achieve the desired divergence among the abutments for the appropriate retention of the restoration. In addition, if necessary, the top of one or more of the Universal Abutments can be modified to facilitate the placement of the prosthesis intraorally (Fig 11-24).

After making an implant-level transfer impression of four implants and pouring a stone model with implant analogs, the technician selects and confirms that the abutments have 2 to 3 degrees of divergence. The degree of divergence can be confirmed with a Girod-Tast or similar device (Fig 11-25). Ideally, the abutments should be positioned with a supragingival margin to facilitate hygiene unless there are aesthetic concerns. Once the appropriate retentiveness has been confirmed with a resin verification jig, the technician must fabricate a resin seating jig and mark it, as well as the stone model and abutments, to facilitate not only the placement sequencing but also the intraoral positioning of the abutments for the clinician. Fig 11-26 (a) Light-cured resin seating jig on a stone model with numeric markings indicating the first two maxillary abutments in the sequence to be seated. (b) Left profile view of light-cured resin seating jig on a stone model indicating the second and third maxillary abutments in the sequence to be seated. (c) The red arrow indicates that the abutments should first be loosely seated in the well of the implant before being engaged by the seating jig. (d) Light-cured resin seating jig seated intraorally. (e) This seating jig was cut into two pieces to facilitate the seating of the abutments. This prevented a need to initially seat an abutment into the well of the implant before engaging the seating jig.

After fabrication of the resin seating jig, the two most parallel abutments are chosen and marked on their prosthetic heads with a numeral 1 to represent the initial abutments to be seated. If their posts were modified, the abutments’ facial surfaces are marked with a line or wider groove to facilitate their proper positioning in the seating jig. Then as a unit, the two incompletely seated abutments are loosely placed in the resin seating jig and transported to the stone model to initially confirm their seating potential in the implant analogs within the model prior to their being seated in the mouth (Figs 11-26a and 11-26b). If the shafts of the two abutments are successfully placed into their corresponding implant analogs, their positions in the model and seating jig are marked with a numeral 1. Petroleum jelly is applied into the bores of the seating jig to facilitate its removal from the abutments once they have been inserted into the implants. Subsequently, this procedure is followed for the remaining abutments, either individually or collectively, and their confirmed sequence is numerically indicated on the cast and on the seating jig. Angled abutments may require a preliminary loose seating in the implant well prior to their being engaged in the seating jig. Such a need is indicated on the cast and on the seating jig with an arrow (Figs 11-26c and 11-26d). Alternatively (and often easier), the resin seating can be cut into two pieces and used separately (Fig 11-26e). If an abutment has been modified, its facial surface is marked with a line, or deepened groove, to facilitate its positioning.

the retentiveness and the path of insertion for the proposed TRINIA prosthesis. Petroleum jelly is applied into the bores of the chosen milled copings prior to their being seated onto the Universal Abutments in the model to facilitate their removal once they are cemented into the verification jig. If the resin verification jig is retentive and has a path of insertion on the model, the final prosthesis should also have a path of insertion and retentiveness.

The above process is repeated for the intraoral seating of the TRINIA prosthesis. A bonding agent may be applied to the bores of the TRINIA prosthesis to facilitate the adherence of the resin cement to the TRINIA prosthesis. The resin cement mechanically attaches to the circumferential grooves on the milled titanium copings.

Whether a TRINIA substructure is to be restored with composite denture teeth or custom polyceramic handcrafted teeth depends on the desire of the clinician, the aesthetic skills of the technician, and the finances of the patient, as well as the nature of the opposing dentition. Although prefabricated composite denture teeth provide the opportunity for achieving excellent aesthetic restorations more readily than handcrafted custom teeth, they are not as wear resistant; therefore, their use should be avoided when the opposing arch comprises natural teeth or ceramic restorations. Additionally, to preserve the patient’s vertical dimension of occlusion, a polyceramic material may be bonded to the occlusal surface of several denture teeth to increase their resistance to wear.

After the successful seating of all the abutments in the model, a resin verification jig must be fabricated to confirm Fig 11-27 (a) Facial view of four nonparallel guide pins in implant analogs. (b) Stone model with two posterior Universal Abutments with purple retentive copings and two anterior modified abutments with custom-made telescopic copings. (c) Intaglio view of maxillary prosthesis fabricated with cream-colored TRINIA to enhance aesthetics through the denture teeth after intraoral cementation of copings. (d) Facial view of maxillary prosthesis fabricated after intraoral cementation of retentive copings. (e) Intaglio view of mandibular prosthesis fabricated with pink-colored TRINIA to enhance aesthetics after intraoral cementation of copings. (f) Facial view of mandibular prosthesis fabricated prior to intraoral cementation of retentive copings. —_>

Maxillary and Mandibular Full-Arch Telescopic Prostheses

The treatment of a 58-year-old woman with maxillary and mandibular full-arch TRINIA telescopic restorations demonstrates many aspects of telescopic prostheses. Two full-arch implant-level transfer impressions were made and their interarch relationships recorded prior to the pouring of master stone models with implant analogs. Eight abutments were then selected, four of which were modified for the fabrication of two light-cured resin verification jigs and two seating jigs. Subsequently, two definitive TRINIA substructures and prostheses were fabricated with two purple retentive and two custom telescopic copings for each arch. Four custom telescopic copings were needed because of the nonparallel trajectories of the placements of the four anterior implants, which necessitated the use of modified angled abutments (Fig 11-27a). The maxillary prosthesis used cream-colored TRINIA, and the mandibular prosthesis used pink-colored TRINIA for aesthetic reasons (Figs 11-27b to 11-27f).

Nonverbal communication between the fabricating tech nician and the inserting clinician was provided by red markings on the models, seating jigs, and abutments. The numerals indicated the sequence for loosely placing and transporting abutments into the seating jig as well as for orienting and seating them in the wells of their implants. Because the two anterior abutments in both arches were angled abutments that had to be modified, purple prefabricated retentive copings could not be used, thus necessitating the fabrication and use of custom-cast telescopic copings.

The red lines on the models, seating jigs, and abutments facilitated the orientation and seating of the modified abutments (see Fig 11-27b). The red arrows indicated that the abutments must be initially seated loosely in the wells of the implants prior to engaging the seating jig to definitively seat them. Once all of the abutments were seated, the prostheses were tried in to confirm their fit over the abutments. The prostheses were then seated a second time, after the copings were filled with petroleum jelly and placed onto their respective abutments (Figs 11-27g and 11-27h).

After confirmation of the fit of the prostheses over the copings, the outer surface of the copings and the bores of the TRINIA prostheses were cleaned with alcohol (Fig 11-27i). The copings were then cemented with resin cement into the TRINIA prostheses (Fig 11-27j). To conclude the restoration, any extraneous cement was removed, and the occlusion was checked once more before the patient was given maintenance instructions and dismissed (Figs 11-27k to 11-27m).

The location and quantity of a patient’s teeth and bone will dictate both the sequencing and restorative nature of their treatment. If sufficient teeth are present, it is often prudent to place the implants and make an implant-level transfer impression for the final TRINIA telescopic restoration during the implant uncovering appointment. Even compromised teeth can not only provide function and aesthetics for the patient during the period of osseointegration, but also facilitate the recording of occlusal relationships and selection of aesthetic and functional teeth arrangements for both the dentist and technician. The ease with which a TRINIA prosthesis can be relined intraorally facilitates delaying the removal of the patient’s remaining teeth until the day the definitive restoration is placed.

Although Bicon’s clinical advice since 2010 has been to use a minimum of four implants for both the mandible and maxilla to support a TRINIA prosthesis, we now believe a TRINIA telescopic prosthesis may be successfully supported on only three implants for virtually all atrophic jaws; therefore, we are Fig 11-27 (cont) (g) Petroleum jelly was applied to a custom telescopic coping. (h) Custom telescopic coping filled with petroleum jelly was placed onto its respective abutment. The retentive telescoping copings were also filled with petroleum jelly prior to placement on their respective abutments. (i) The surface of the telescopic copings was cleaned with alcohol prior to placement of the prostheses. (j) Resin cement was applied to the bores of the mandibular TRINIA prosthesis. (k) Maxillary TRINIA prosthesis was seated with a white Healing Abutment attached to a straight handle. (l) Mandibular TRINIA prosthesis was placed onto the custom milled telescopic copings for their cementation into the bores of the prosthesis. (m) A proxy brush was used to remove any extraneous cement around the maxillary prosthesis. currently evaluating treatments with only three implants supporting full-arch TRINIA telescopic restorations. In the maxilla, we are placing an implant in each tuberosity and the incisive foramen. In the mandible, we are placing three implants in the interforaminal bone to support a bilateral cantilevered prosthesis. Hopefully, our clinical evaluations will confirm our hypothesis for the benefit of patients in need.

TRINIA-HC and Gothic Arch Tracing

TRINIA is a versatile material that can be used in conjunction with a variety of superstructures such as composite denture teeth, polyceramic handcrafted teeth, and recently with Shofu’s HC Ultra disc material, which can be successfully and efficiently milled to provide anatomical teeth arrangements that are bonded to TRINIA substructures. To account for the different flexural strengths of the materials, the HC material is milled into three separate pieces prior to being bonded to the single-piece TRINIA substructure. Aesthetic enhancement of these TRINIA-HC restorations can be achieved by applying polyceramic paste material to either the TRINIA or HC material. The following treatment demonstrates the techniques and clinical advantages of combining these two CAD/CAM materials. A 75-year-old patient had a 10-year-old tissue-borne mandibular O-ring overdenture on three O-ring abutments, which was replaced with a new implant-borne telescopic TRINIA-HC prosthesis.

During the first clinical visit, the three O-ring abutments were removed from their implants, and three 2.0-mm impression posts and their corresponding acrylic sleeves were inserted for the making of a full-arch implant-level transfer impression. An initial occlusal registration was recorded using modified acrylic impression sleeves at the patient’s existing vertical dimension of occlusion (VDO) with the bite registration material Capture (Glidewell Direct) (Figs 11-28a to 11-28c). While the patient waited, the impressions were poured, and the stone models were articulated for the fabrication of a maxillary stylus and mandibular tracing plate to facilitate the registration of the patient’s centric relation, utilizing a Gothic arch occlusal registration tracing.

Although the Gothic arch tracing technique has existed for over 100 years, it is not widely known nor widely used. It was introduced by Professor Alfred Gysi in 1910, when he addressed the importance of recording accurate centric relations, hypothesizing that the aesthetics, function, and phonetics of dental prostheses would improve with correct occlusal alignments.[4–6] Despite the early introduction of Gothic arch tracings in dentistry, many clinicians have difficulty managing the execution of the tracings and the assemblage of its components, which in part relies on Fig 11-28 (a) Preoperative radiograph of three implants with O-ring abutments. (b) Patient’s 10-year-old tissue-borne O-ring overdenture. (c) Three violet 2.0-mm impression posts with corresponding red acrylic sleeves seated in their implants. (d) Metal stylus is positioned to scribe on mandibular metal tracing plate during the random movements of the patient’s mandible at a given VDO. (e) Modified wax rim and metal plate with Gothic arch image (arrow) drawn by the random movements of the patient’s mandible. (f) Bore of plastic disc positioned over apex of drawn Gothic arch prior to being luted in place with sticky wax. (g) Stylus positioned in bore of plastic disc for the recording of the patient’s centric occlusal relationship at a given VDO. (h) Bite registration material is injected around the wax rim for the recording of the centric occlusal relationship, while the stylus is positioned in the bore of the plastic disc. (i) Articulated models with the Gothic arch positioning device in place. (j) Three pieces of milled Shofu HC teeth prior to their being bonded onto the TRINIA framework. (k) Bonding agent is applied to TRINIA substructure. the cooperation of the patient. Figures 11-28d to 11-28i demonstrate the process of positioning the stylus for this patient in the maxillary arch to scribe a Gothic arch on the mandibular metal plate, as well as the posttracing images of the assemblage luted with wax to capture the exact position of the patient’s centric relation at a given VDO.

After the recording of the patient’s centric relation, the O-ring abutments were reinserted, and the Gothic arch occlusal registration was sent to the dental technician for the articulation of the stone models and the fabrication of the telescopic TRINIA framework to which three separate,

milled teeth arrangements of Shofu’s HC material were bonded to form the telescopic TRINIA-HC prosthesis (Figs 11-28j and 11-28k). Because both TRINIA and Shofu’s HC are CAD/CAM materials, they offer the many advantages of digital prosthetics to technicians and clinicians alike. Aesthetic enhancement of the gingival area of the prosthesis was provided by the application of the polyceramic paste material Ceramage (Figs 11-28l and 11-28m).

During the second clinical visit, the O-ring abutments were removed, and the three Universal Abutments were inserted into their implants, utilizing a light-cured resin orientation and seating jig, prior to the resin cementation of the three milled retentive copings into the bores of the TRINIA-HC prosthesis (Figs 11-28n to 11-28p). After minor intraoral modifications of the prosthesis, it was polished chairside and subsequently delivered to the patient. The combination of the TRINIA framework and Shofu’s HC superstructure teeth arrangement was both time- and cost-effective for the clinician, the dental technician, and—most importantly—the patient. Fig 11-27 (cont) (l) View of prosthesis prior to addition of Ceramage polyceramic paste material. (m) View of prosthesis after addition of Ceramage polyceramic paste material for gingival aesthetics. (n) Three retentive copings seated on Universal Abutments on stone model. (o) View of finished prosthesis. (p) View of TRINIA-HC hybrid telescopic mandibular prosthesis prior to the removal of extraneous resin cement.

This product combination is an excellent way of replacing mandibular tissue-borne O-ring or Locator overdenture prosthetics with implant-borne telescopic TRINIA restorations on two or three Bicon implants with seemingly excessively long cantilevers.

ed IAIs of screw-in abutments. Polyceramic composites and TRINIA are two metal-free materials that have given the Bicon clinician previously unheard-of restorative flexibility.

The successful treatments of a number of difficult clinical situations have been presented and have exhibited the versatility of Bicon implants and restorative techniques. Shown mainly from a technician’s perspective, the cases in this chapter demonstrate how the IAI and other Bicon features can provide outstanding aesthetics and function with significant savings of time and money. The use of TRINIA and short implants to restore extremely atrophic jaws without the need for additional augmentation procedures has also been exemplified. The upcoming chapters discuss implant placement and restorative procedures in extreme clinical scenarios and diseased states.

Conclusion

The geometric design of the Bicon implant and its components provides for many unmatched clinical capabilities. The Bicon abutment with its hemispheric base, a seemingly innocuous design feature, provides for unequalled cervical aesthetics, emerging from the gingiva as it does. Another feature, and one of the hallmarks of the Bicon system, is the locking-taper IAI, which most importantly provides abutments with 360 degrees of universal positioning. This feature not only frees clinicians from the burden of corralling a tangle of small screws but also provides for unique clinical capabilities such as using a prosthesis to initially orient and seat abutments. While compatible with all conventional prosthetic techniques, the locking-taper IAI also permits the user to employ novel techniques with metal-free materials, which in turn offer a host of significant advantages that are not possible with the thread-

References

1. Bonfante EA, Suzuki M, Carvalho RM, et al. Digitally produced fiber-reinforced composite substructures for three-unit implant-supported fixed dental prostheses. Int J Oral Maxillofac Implants 2015;30:321–329.

2. Urdaneta RA, Seemann R, Dragan IF, Lubelski W, Leary J, Chuang SK. A retrospective radiographic study on the effect of natural tooth-implant proximity and an introduction to the concept of a bone-loading platform switch. Int J Oral Maxillofac Implants 2014;29:1412–1424.

3. Urdaneta RA, Marincola M, Weed M, Chuang SK. A screwless and cementless technique for the restoration of single-tooth implants: A retrospective cohort study. J Prosthodont 2008;17:562–571.

4. El-Gheriani AS, Winstanley RB. The value of the Gothic arch tracing in the positioning of denture teeth. J Oral Rehabil 1988;15:367–371.

5. Gysi A. The problem of articulation. The Dental Cosmos 1910;52:1–19.

6. Rubel B, Hill EE. Intraoral Gothic arch tracing. N Y State Dent J 2011;77(5):40–43.

12

Sinus Lift Techniques

Mauro Marincola | Shadi Daher | Rolf Ewers | Jeffrey Lehrberg

Despite the relative ease with which implants can be placed under ideal circumstances, there are often times when normal variations in morphology, long periods of edentulism, or consequences of disease or injury can pose difficulties. Whatever the etiology, a condition that frequently makes the placement of implants difficult in the posterior maxilla is a lack of sufficient bone height. Fortunately, there is a reliable procedure that can be employed to overcome insufficient bone in the posterior maxilla: the sinus lift.

The sinus lift (also known as sinus floor elevation , maxillary sinus floor augmentation , sinus augmentation , sinus procedure , or sinus graft ) is an augmentation procedure that involves gently lifting the sinus mucosal lining and introducing in the space created a material that will stimulate or allow bone growth to occur. By performing a sinus lift, the clinician can increase the maxillary alveolar process depth for the placement of a dental implant.

In general terms, there are two distinct approaches to the sinus floor for augmentation. The lateral approach is through the buccal surface of the alveolar process, and the vertical approach is through the occlusal surface of the crest. There are three distinct sinus lift procedures discussed in this chapter: (1) internal, (2) crestal, and (3) lateral. The internal and crestal techniques are variations of the vertical approach. After briefly discussing sinus lift theory and anatomical considerations, detailed instructions and case reports are provided to aid clinicians in utilizing these techniques for their patients.

Table 12-1 Recommended treatment options based on residual bone height and implant size

Background

The idea of augmenting the sinus floor was first proposed by Tatum in a 1976 lecture and documented 4 years later by Boyne and James.[1,2] These early procedures aimed to increase alveolar bone height to allow the placement and support of implanted prosthetic devices.[2]

Early sinus lift procedures contained the following hallmarks: the opening of a full-thickness flap to expose the lateral wall of the sinus cavity using scalpels, rotary instruments, and osteotomes to create an antrostomy to expose the Schneiderian membrane; displacing the membrane from the bone with curettes and elevating it; and finally, filling the newly created void with autogenous bone from the iliac crest.[2–4] Although these early sinus lift procedures were effective, they were also highly invasive with the potential for complications. A less invasive alternative to the lateral antrostomy was introduced by Summers in 1994.[5]

For Summers’ new technique, a crestal osteotomy was prepared, after which osteotomes and osteoexpanders were used to make a comminuted fracture of the sinus floor.[5,6] The Schneiderian membrane was then elevated using autogenous or synthetic bone-grafting materials.[5,6]

Since the idea of a sinus lift was first proposed, advancements in our understanding of the biology and science of implants has helped to refine the procedure and introduce a number of new techniques and efficacious graft materials.[7,8]

Contraindications

As is the case with any surgical procedure, individual patient health histories and overall patient health (eg, age, blood pressure) should be taken into account prior to attempting any surgical manipulation. Furthermore, prior to any surgery, the patient must be assessed for any pathology, developmental disorder, or other injury that would contraindicate sinus surgery. Even asymptomatic phenomena, such as large mucous retention cysts, should likewise be treated prior to attempting a sinus lift; the volume and weight of such a lesion might affect the mechanical stability of the graft or implant and should be treated prior to proceeding.

Internal Sinus Lift Techniques

Presurgical analysis and planning

A major part of sinus lift surgical planning is determining which implant system to use, as this can influence which type of sinus lift procedure will be implemented. Implant selection is a function of both implant and surgical site characteristics, and selecting the right implant system can increase the variety of surgical modalities available to the clinician. Because of the short implant length and other key features (see chapter 2), the Bicon implant system provides a degree of flexibility and versatility that is not available with other implant systems. Table 12-1 and Fig 12-1[9] provide guidance with respect to different treatment options based on residual bone height and implant size. Fig 12-2 (a) Radiograph with measurements of bone heights of the residual alveolar crest from mesial to distal. (b) Sagittal illustration of the intended location of two implant sites in the maxillary second premolar and first molar areas. (c) Transverse section of the residual crestal bone in the anterior segment of the maxillary second premolar. Dashed lines depict the maximum available bone height in the buccal (3.0 mm) and palatal (6.0 mm) regions of the alveolar crest. (d) Dashed lines mark locations where additional measurements should be taken.

The ultimate goal of all maxillary sinus lift procedures is to reclaim sufficient bone volume of the alveolar process to place an implant. The goal of the internal sinus lift (ISL) procedure is to reclaim bone volume with a minimally invasive approach, typically carried out through a prepared implant osteotomy. To perform sinus lift techniques effectively, it is necessary to have a good understanding of the anatomy involved and how tissues respond to manipulation. The maxillary sinuses are a pair of pyramid-shaped cavities in the body of the maxilla whose mucosal lining functions to protect against inhaled particulates and pathogens. Lining the maxillary sinus is a layer of mucoperiosteum called the Schneiderian membrane; it is this membrane that is lifted during a sinus lift procedure, creating a newly formed space that is filled with bone or augmentation material.

Radiographic examination of a sinus will reveal that the corners (or points) of the pyramid shape are actually rounded or curved; this curvature must be taken into account when performing a sinus lift (Figs 12-2a to 12-2c). Prior to surgery, the dimensions of the future osteotomy should be measured using a presurgical radiograph or cone beam computed tomography (CBCT) scan; these measurements will come into play later and serve to aid the clinician during the procedure. To make the presurgical measurements, record the length of the distance from the sinus floor to the alveolar crest at three points: one at the center of the intended location of the osteotomy site and two that take into account the diameter of the osteotomy (eg, 5.0 mm for a 5.0-mm implant) in the sagittal and transverse dimensions (Fig 12-2d). These simple measurements account for the curvature of the sinus and will provide the clinician with pertinent information about the depth at which the sinus floor will be encountered.

Box 12-1 ISL quick guide

Recommended armamentarium

• Local anesthesia

• Scalpel with no. 15 blade

• 1- to 5-mL syringe

• Radiographs with measurements (see text)

• 2.0-mm pilot drill

• Latch Reamers

• Hand Reamers (threaded straight handle)

• 4.0-mm Osteotome

• Dappen dish

• Bone-Graft Syringe

• SynthoGraft (0.25 to 1.50 g of 50- to 500- μm particle size)

• Periosteal elevator

• Cotton swabs

• Implant Inserter/Retriever with seating tip

• Bicon dental implants (5.0 × 5.0–mm implant recommended)

• Sinus Lift Abutment (recommended)

• Bicon Surgical Kit

Step-by-step procedure

1. Make radiographic measurements (see text).

2. Administer anesthesia without epinephrine.

3. Create a full-thickness flap that exposes the mesiodistal and buccopalatal edges of the alveolar crest.

4. Collect any blood and autogenous bone from the wound and store it in the dappen dish.

5. Readminister anesthesia, this time with epinephrine.

6. Using the 2.0-mm pilot drill, mark the location of the future osteotomy by drilling through the cortical bone of the alveolar crest.

   • Important: Stop drilling before perforating the sinus floor.

7. Refer to radiographic measurements: At the location of the osteotomy, the shortest vertical mesiodistal depth measured will indicate the maximum depth the Latch Reamers should be inserted (see text for in-depth explanation).

ISL procedure

A step-by-step quick guide for the internal sinus lift procedure can be found in Box 12-1. For all sinus lift procedures, we recommend reviewing the entire relevant sections first and then using the quick guides as a reference prior to performing the actual procedure.

The first step in the ISL procedure is to obtain radiographic studies, followed by administering local anesthesia. Initially, an anesthetic without epinephrine is recommended to facilitate the collection of a sufficient amount of blood for later use. Following the collection of an adequate amount of blood, anesthesia with epinephrine may be used.

The following treatment demonstrates the ISL procedure. After administering anesthesia, a full-thickness flap was raised to expose the mesiodistal and buccopalatal boundaries of the alveolar crest (Fig 12-3a). Blood was col-

8. Using the Latch Reamers, begin to widen the osteotomy in the cortical bone only to the final implant diameter by sequentially increasing reamer diameters.

9. Using the 3.5-mm Hand Reamer attached to a straight handle, extend the depth of the osteotomy by removing spongy bone up until the cortical layer of the sinus floor and has been reached, and save any collected bone in a dappen dish for later use.

10. Using the 3.5-mm Hand Reamer, tap very carefully at four different locations along the buccopalatal and mesiodistal axes of the sinus floor cortical bone and save any collected bone in a dappen dish for later use.

11. Take the Bone-Graft Syringe, and aspirate up to 5 mL of blood from the surgical site, and add the blood to the dappen dish (typical sites yield around 1 mL of blood).

12. Slowly pour the SynthoGraft into the dappen dish and mix it with the blood using the periosteal elevator until it is completely wetted or has a putty-like consistency.

13. Using the Bone-Graft Syringe, aspirate the SynthoGraft and blood mixture and inject it into the osteotomy until resistance is felt; then, while still injecting, retract the syringe.

14. Using the Osteotome, advance the graft deeper into the osteotomy to raise the fractured cortical bone of the sinus floor and sinus mucosa.

15. Place the implant into the osteotomy using the implant Inserter/ Retriever, ensuring that when finally seated, the coronal part of the implant rests 2.0 to 3.0 mm below the alveolar crest of bone.

16. Disengage the implant Inserter/Retriever.

17. Insert either a black Healing Plug or a Sinus Lift Abutment into the implant with its wider side oriented buccolingually, and gently tap it into place.

18. Add any autogenous bone or SynthoGraft under and around the oval head of the Sinus Lift Abutment.

19. Suture the flap to conclude the procedure.

lected with a syringe at the site and mixed with SynthoGraft in a dappen dish (Fig 12-3b). A 2.0-mm pilot drill was used to mark the location and prepare the initial osteotomy in the alveolar crest. After referring to the measurements discussed in the presurgical analysis and planning section of this chapter, use the two-handed technique to drill the osteotomy. Be mindful to stop drilling before perforating the sinus floor.

At the location chosen for the osteotomy, the shortest apicocoronal length measured will indicate how deep the Latch Reamers may be advanced before encountering the cortical bone of the sinus floor (see Fig 12-2d). Using the Latch Reamers, widen the crestal cortical bone to the final intended implant diameter. When using the Latch Reamers, it is important to only widen the osteotomy in areas composed of cortical bone in the alveolar crest to prevent encountering and damaging the cortical bone of the sinus floor (Fig 12-3c). Fig 12-3 (a) A full-thickness flap is raised, exposing the mesiodistal and buccopalatal boundaries of the alveolar crest. (b) A syringe is used to collect blood as a wetting agent for SynthoGraft. (c) Radiograph of Latch Reamers widening the crestal cortical bone. (d) Preparing the osteotomy with a 3.5-mm Hand Reamer. (e) Radiograph showing the extent to which the 3.5-mm Hand Reamer should be advanced (ie, up until the cortical layer of bone of the sinus floor).

Once the osteotomy had been expanded to its intended diameter, the 3.5-mm Hand Reamer attached to a straight handle was inserted and advanced to remove spongy bone up until the cortical layer of bone of the sinus floor (Figs 12-3d and 12-3e). Then, using the 3.5-mm Hand Reamer (or a Hand Reamer narrower than the diameter of the osteotomy), carefully tap the sharp tip of the Hand Reamer at four different points along the buccopalatal and mesiodistal axes to facilitate a comminuted microfracture of the sinus floor’s cortical bone (Fig 12-3f). The Hand Reamer has a single vertical cutting edge that ends at the apex of the reamer. It is important to be aware of this design and how the instrument is inserted when performing this procedure (Fig 12-3g). The exact locations within the osteotomy where the points of microfracture will occur along the buccopalatal and mesiodistal axes are illustrated in Fig 12-3h. Based on the presurgical measurements, the initial point of microfracture should occur at the location of bone with the shortest apicocoronal height. Before advancing to the next step, examine the sinus floor to determine if the membrane is intact or the sinus mucosa has been perforated (Fig 12-3i).

The next phase of the ISL procedure concerns the preparation and application of the bone-grafting material SynthoGraft. The selection of a bone-grafting material is important, especially where plateau-root form implants are concerned (see chapter 19). After being mixed, the material should have a consistency that facilitates its infiltrating between the plateaus of the implant; permitting bone regeneration to occur between the plateaus ensures the future stability of the implant. For the treatment depicted here, SynthoGraft mixed with the patient’s blood was used as the bone-grafting material. Before preparing the SynthoGraft mixture, as much blood as possible was collected with a 1 or 5-mL syringe (see Fig 12-3b). The clinician should try to aspirate as much blood as the syringe permits (typically at this stage of the procedure, the surgical site may only yield between 0.5 and 1.0 mL of blood) and add it to the previously collected blood in the dappen dish. To prepare the SynthoGraft, slowly pour the material into the dappen dish while simultaneously mixing it with the patient’s blood using a periosteal elevator. Once the SynthoGraft and blood mixture is completely wetted and has a putty-like consistency or adheres to the periosteal elevator, it is ready to be used. If the mixture is overly wet, use a cotton swab to absorb the excess blood.

Using the Bone-Graft Syringe, the SynthoGraft mixture is collected and slowly injected into the osteotomy (Fig 12-3j). During the injection, once resistance against the Schneiderian membrane is detected, slowly retract the syringe while still continuously injecting (Figs 12-3k and 12-3l).

After the bone-graft material had been injected, a 4.0mm Osteotome was used to gently push the material into the osteotomy (Fig 12-3m). This step has two purposes: first, it helps further induce the comminuted fracture in the cortical bone; second, the graft material acts as a buffer between the sinus mucosa and the cutting edge of the Osteotome, preventing possible damage to the mucosa (Fig Fig 12-3 (cont) (f) Depiction of the four points along the buccopalatal and mesiodistal axes that are weakened by a gentle tapping of the sharp point of a Hand Reamer into the bone of the sinus floor. —_>>

12-3n). With the graft material in place, the Osteotome was advanced further via gentle tapping until the cortical bone was fully fractured and the sinus mucosa was elevated (Fig 12-3o). It is important to remember that the Osteotome is not used to lift the sinus mucosa but rather to raise the cortical bone and sinus mucosa by pushing on the graft; therefore, do not attempt to forcibly lift the floor with the Osteotome, as this may damage the sinus mucosa.

The next step of the procedure is the insertion and seating of the implant. For most ISL procedures, a 5.0 × 6.0– mm implant with a Sinus Lift Abutment is recommended (depending on implant location and surrounding anatomy). Using the Implant Inserter/Retriever instrument, the implant was inserted into the osteotomy and seated into place by tapping (Fig 12-3p). When placing the implant, it is recommended that the implant be slowly spun or rotated during its insertion; this can be achieved simply by twisting one’s wrist while inserting. Twisting or spinning the implant helps allow for an even distribution of blood and SynthoGraft between the implant’s plateaus. The implant’s coronal-most part (ie, where the abutment will be placed) should reside at least 1 to 2 mm below the alveolar crest. Once the implant is securely seated within the osteotomy, the Implant Inserter/Retriever instrument is disengaged.

the implant well. The Sinus Lift Abutment is recommended because it stabilizes the implant in its intended position, especially in instances where there is little to no retention afforded by the walls of the osteotomy. The Sinus Lift Abutment has a narrow side and a wide side; if possible, it is preferable to have the wide side oriented buccolingually to allow for it to be fully seated, which avoids the possibility of the wider side coming into contact with adjacent teeth (Fig 12-3q). However, it is the clinician’s responsibility to decide the orientation of the Sinus Lift Abutment to safeguard not only the stability of the implant, but also the integrity and blood supply of the flap. This is particularly important when using larger Sinus Lift Abutments. After placing the Sinus Lift Abutment into the implant, any remaining SynthoGraft and autogenous bone mixture was placed under and around the oval head of the abutment. The abutment was then tapped into place using a standard seating tip attached to a threaded handle (Fig 12-3r). If the implant is not seated at least 2 mm below the apex of the alveolar crest, it may be tapped further during the seating of the abutment. Finally, the flap was sutured closed, and the patient was provided with postoperative instructions and care. Figure 12-3s shows the postoperative radiograph, illustrating the combination of the implant, Sinus Lift Abutment, and graft.

Subsequent to placing the implant, either a Healing Plug or a provisional Sinus Lift Abutment is gently tapped into Fig 12-3 (cont) (g) Design differences between a 3.5-mm Latch Reamer and Hand Reamer. The Hand Reamer possesses a single vertical cutting edge that ends at the apex of the reamer. (h) The four points on the cortical bone of the sinus floor to be weakened with a Hand Reamer after it is inserted into the osteotomy. These create comminuted fractures along the buccopalatal and mesiodistal axes (indicated by targets ). (i) Palatal view showing that the Schneiderian membrane and fractured cortical bone fragments remain intact. (j) A 4.0-mm Bone-Graft Syringe is shown prior to aspirating a SynthoGraft and blood mixture in a dappen dish. (k) Injecting SynthoGraft into an osteotomy. (l) Appearance of the osteotomy immediately after the injection of SynthoGraft. (m) A 4.0-mm Osteotome is used to advance the graft material further into the osteotomy. (n) Illustration showing the correct use of the 4.0-mm Osteotome when advancing the graft material. (o) Radiograph showing how the SynthoGraft has been advanced by the Osteotome. (p) Placing the implant with the Inserter/Retriever. (q) A Sinus Lift Abutment is placed into the implant. (r) The Sinus Lift Abutment is tapped into place using a standard seating tip. (s) Radiograph showing the results of a successful ISL procedure.

Box 12-2 ISL/crestal window hybrid procedure quick guide

Recommended armamentarium

• Local anesthesia

• Scalpel with no. 15 blade

• Dappen dish

• 5.0-mm sinus lift osteotome

• 1-mL syringe • Resorbable collagen barrier membrane • 2.0-mm pilot drill (optional) • Latch Reamers

• Hand Reamers (threaded straight handle)

• 4.0-mm Osteotome

• Bone-Graft Syringe

• SynthoGraft (0.25 to 1.50 g of 50- to 500-μm particle size)

• Periosteal elevator

• Cotton swabs

• Periodontal probe (optional)

• Implant Inserter/Retriever with seating tip

• Bicon dental implant (5.0 × 5.0–mm implant recommended)

• Sinus Lift Abutment (recommended)

• Bicon Surgical Kit

• Step-by-step procedure

• 1. Take preoperative radiographs to determine the extent of the defect. 2. Attempt alternative conservative therapies (optional). 3. Administer anesthesia.

4. Retract the lip and expose the surgical site.

5. Create a full-thickness flap that exposes the lateral wall of the sinus (avoid the roots of adjacent teeth).

6. Using a Shepherd bur at high speed with copious irrigation, create an antrostomy on the lateral wall of the sinus (Caldwell-Luc approach).

ISL/crestal window hybrid procedure

Some clinical situations call for an ISL to be performed with a simultaneous bone graft; this hybrid procedure is known as the ISL/bone graft or the ISL/crestal window hybrid. The crestal window technique is presented in a detailed discussion later in this chapter. ISL/crestal window hybrid procedures are frequently required following the pathologic or iatrogenic loss of the buccal plate of the osteotomy. When the buccal plate of the osteotomy is lost, it creates an opportunity to directly visualize the sinus floor—a characteristic that the ISL/crestal window hybrid takes advantage of to facilitate the treatment. The ISL/crestal window hybrid allows the lifting aspect to be visualized, providing a measure of visual control that is otherwise limited in the normal ISL procedure. A step-by-step quick guide for the ISL/bone graft hybrid procedure can be found in Box 12-2.

As is the case for the normal ISL procedure, the first step of the ISL/crestal window hybrid procedure is to determine the full extent of the defect by undertaking the necessary radiographic studies (Fig 12-4a). In the following treatment illustrating this technique, a healthy 59-year-old woman presented with a tender maxillary right premolar displaying mobility. Further examination revealed an unsalvage-

7. Fracture the window and displace it vertically.

8. Breach the sinus wall and allow evacuation of contents (eg, infection, blood, pus).

9. Using the Latch Reamers, begin to widen the osteotomy to the final implant diameter by sequentially increasing reamer diameters and save any collected bone in a dappen dish for later use.

10. Using the Hand Reamers (straight handle), widen the osteotomy to the final implant diameter by sequentially increasing reamer diameters and save any collected bone in a dappen dish for later use.

11. Using a 1-mL syringe, collect blood from the surgical site.

12. Slowly pour the SynthoGraft into the dappen dish and mix it with blood (obtained from surgical site or via venipuncture) using the periosteal elevator until it is completely wetted or has a putty-like consistency (autogenous bone may also be used).

13. Trim a collagen resorbable membrane so that it overlaps the edges of the defect by 2 to 4 mm.

14. Very slowly and gently, use the Bone-Graft Syringe to aspirate the SynthoGraft and blood mixture and inject it into the osteotomy.

15. Place the implant into the osteotomy using the Implant Inserter/ Retriever, ensuring that when finally seated, the coronal part of the implant rests 2 mm below the alveolar crest.

16. Verify the angle of the implants with guide pins.

17. Disengage the Implant Inserter/Retriever.

18. Seat the implant with the seating tip (optional).

19. Insert either a black Healing Plug or a Sinus Lift Abutment into the implant with its wider side oriented buccolingually and gently tap it into place.

20. Apply any remaining autogenous bone and/or SynthoGraft to the exposed implant surfaces.

21. Suture the flap to conclude the procedure.

able tooth because of severe bone loss and mobility and an acute periapical infection caused by a root fracture. A treatment plan for the replacement of the tooth with an implant and an Integrated Abutment Crown (IAC) was initiated. The afflicted tooth was extracted, and the site was allowed to heal for 10 weeks (Figs 12-4b and 12-4c).

To initiate the surgical phase of the procedure, a papillasparing buccally based full-thickness mucoperiosteal flap was developed and retracted with a suture secured to the vestibular mucosa, which revealed that a significant part of the buccal plate was missing (Fig 12-4d). The next step was to create the crestal window; however, because of the missing buccal plate, the implant osteotomy was developed with Hand Reamers only because the bone was soft and required no additional depth (Figs 12-4e and 12-4f). After the successive application of reamers of increasing diameters, the buccal defect was examined to ensure the presence of a floor for the osteotomy, followed by reaming to the final diameter (Fig 12-4g). Any extraneous bone, including bone collected during the reaming, was saved in a dappen dish for later use (Fig 12-4h). The final reamer was used to widen the osteotomy to the intended implant size (Figs 12-4i and 12-4j). Fig 12-4 (a) Initial periapical radiograph reveals an extensive radiolucency at the apex of the root of the maxillary right first premolar. (b) Radiographic appearance of the site of the maxillary right first premolar after 10 weeks of postextraction healing. Note the proximity of the maxillary sinus floor. (c) Preoperative clinical appearance reveals atrophy of the interproximal papillae with gingival recession around adjacent teeth. (d) Clinical image revealing a buccal bony defect and a buccally based full-thickness mucoperiosteal flap being retracted with a suture secured to the vestibular mucosa. (e) Because the bone is soft and requires no additional depth, the implant osteotomy is initially formed with Hand Reamers only. The 2.5-mm Hand Reamer is used to start the process, and then 3.0-, 3.5-, and 4.0-mm Hand Reamers are used in succession to widen the osteotomy. (f) As the 4.0-mm Hand Reamer is used, the buccal plate defect becomes more pronounced. (g) The buccal defect after removing bone particles and confirming the presence of an osteotomy floor. (h) All bone particles are collected as the integrity of the osteotomy walls is confirmed. (i) Clinical view of the osteotomy prior to its final widening with a 5.0-mm Hand Reamer. (j) The 5.0-mm Hand Reamer is used to widen the osteotomy for a 5.0 × 8.0–mm implant. (k) A 5.0-mm sinus floor Trumpet Osteotome is used. —>

Next, a Bicon 5.0-mm sinus floor osteotome was used to induce a comminuted fracture of the sinus floor (Fig 12-4k). The sinus floor is usually hidden inside the osteotomy, and fracturing is carried out blindly, or at least without direct visualization; this lack of visual control is considered a major limitation of the ISL technique. In this case, the buccal defect offered the operator a unique opportunity to visualize the contact and mobilization between the osteotomy and the sinus floor (Fig 12-4l). A comminuted fracture was accomplished by gently tapping the Osteotome with a surgical mallet. Blood was collected using a 1-mL syringe (Fig

12-4m). Collecting blood after the floor fracture offered a better chance of harvesting bone marrow cells that could contribute to bone regeneration. Typically, 0.25 to 0.5 mL of blood is sufficient for most single-site ISLs. Note that the blood coagulum often must be broken down into the graft to complete this step. SynthoGraft was slowly poured into the dappen dish and mixed with the collected blood. Before applying the SynthoGraft and blood mixture, a collagen resorbable membrane was trimmed and checked to ensure that it fit over the defect (Fig 12-4n). Fig 12-4 (cont) (l) The Osteotome is seated against the bottom of the osteotomy. This step is usually hidden inside the osteotomy and carried out without direct visualization. The buccal defect in this situation offers a unique opportunity to visualize the Osteotome-to-floor contact and mobilization. A comminuted fracture is accomplished by gently tapping the Osteotome with a surgical mallet. (m) Blood from the surgical site is collected in a 1-mL syringe so it can be mixed with SynthoGraft particles. (n) A collagen resorbable membrane is trimmed to fit the defect. It must overlap the edges of the defect by 2 to 4 mm. Membrane coverage over the crest is typically not necessary. (o) View of the fractured floor of the osteotomy. Note the minimal displacement of the bone segment at the bottom of the osteotomy. (p) A BoneGraft Syringe is used to inject the slurry of SynthoGraft particles and blood into the osteotomy. (q) View of the implant osteotomy after being filled with the putty-like SynthoGraft and blood mixture. (r) The implant is gently introduced into the osteotomy and graft with an Inserter/Retriever instrument. (s) Definitive seating is achieved with gentle tapping of the implant using the inserting tip, which is placed against the bottom of the implant well. (t) The black Healing Plug is trimmed and placed into the implant well with a periodontal probe. (u) The harvested bone particles, which were collected during the preparation of the osteotomy, are placed over the exposed implant surface. (v) Additional mixture of SynthoGraft and blood is placed over the defect. (w) The trimmed collagen membrane is positioned over the graft and tucked under the flap’s edges and the retention suture. (x) The retention suture is tied to secure the membrane and graft in the correct location over the implant and defect. (y) The flap is closed with interrupted resorbable sutures. (z) Postoperative periapical radiograph. (aa) Periapical radiograph taken just before the implant was uncovered, at approximately 6 months. (bb) Note the bone stability both apical and crestal to the implant after years of being in function.

The membrane must overlap the edges of the defect by 2 to 4 mm (coverage over the crest is typically not necessary). At this stage of the procedure, the minimal displacement of the round bone segment was apparent (Fig 12-4o).

The Bone-Graft Syringe was then used to inject the SynthoGraft and blood mixture into the defect (Fig 12-4p). This step should be carried out very gently and slowly to allow the graft particles to infiltrate the space between the sinus membrane and bony floor of the sinus—accomplishing their separation and achieving a sinus lift (Fig 12-4q). Up to 0.5 g of graft particles may be used in this manner; this ensures the presence of an adequate volume to elevate the floor sufficiently. Next, the implant was gently introduced into the osteotomy with an Inserter/Retriever and seated (Figs 12-4r and 12-4s). Using the ISL/crestal window hybrid technique provides excellent visibility and control while placing the implant.

Once the implant had been securely placed, the black Healing Plug was trimmed and placed into the implant well with a periodontal probe after placing the retention suture through the palatal tissues and the periosteum at the base of the buccal flap (Fig 12-4t). Any remaining autogenous bone or SynthoGraft collected during the procedure was then placed over the exposed implant surfaces (Figs 12-4u and 12-4v). The collagen membrane that was trimmed earlier was then positioned over the graft and tucked under the flap’s edges and the retention suture (Fig 12-4w). The retention suture was tied, securing the membrane and graft in the correct location (Fig 12-4x). Finally, the flap was sutured closed, concluding the procedure (Figs 12-4y and 124z). Figures 12-4aa and 12-4bb show the periapical radiographs taken 6 months postplacement, during uncovering and long-term follow-up visits, respectively.

ISL complications

Adhering to the techniques described above will usually result in excellent outcomes; however, like any medical procedure, there is always a chance of complications. One of the most common complications that can arise from the ISL procedure is the rupture or perforation of the Schneiderian membrane. Major ruptures of the membrane are easily observed during the procedure, presenting as a dark, gaping hole at the osteotomy’s apex; an example of this is illustrated in Fig 12-5, where two osteotomies at equivalent steps of the ISL procedure have been prepared: The left osteotomy has an intact membrane, while the right osteotomy exhibits a dark void, indicative of a ruptured membrane.

If the Schneiderian membrane is ruptured, it can be repaired by performing a lateral antrostomy with concurrent suturing or inserting collagen membranes and implant placement; however, this should only be performed by an experienced practitioner.[10,11] If the practitioner is less experienced, it is recommended that a collagen plug be inserted into the osteotomy and the flap sutured closed. The Schneiderian membrane can normally repair itself within 2

Fig 12-5 An intact (left) and ruptured (right) Schneiderian membrane. Note the dark void present in the ruptured membrane.

to 3 months, at which point the procedure may be attempted again.

Crestal Window Techniques

Another sinus floor augmentation technique that takes a vertical approach through the occlusal surface of the crest is the crestal window sinus lift (CSL) or floor transport procedure. In cases where the residual crestal bone height is less than 3.0 mm, a CSL may be used to facilitate the placement of implants. The CSL increases alveolar crest bone depth and allows for increased clinician visibility, all while diminishing the risk of tearing the sinus mucosa. The challenge with the crestal window approach is to ensure proper angulation and primary stability of the implant; fortunately, for many cases, the Sinus Lift Abutment is capable of achieving this. However, primary stability of the implant is still important and should be achieved with friction against the internal walls of the alveolus, if possible; the Sinus Lift Abutment is only an adjunct to help ensure the proper depth of the implant and prevent its displacement into the sinus cavity.

There are many other cases where the internal dimension of the sinus cavity’s extension into the alveolar process are too great (> 6.0 mm) to allow for the widest available Bicon implant to achieve friction with the palatal and buccal walls. For these patients, historically, clinicians would choose the option of a lateral sinus lift either before or during implant placement. Today, their choice would be the less invasive option of using a titanium (Ti)-mesh. Taking advantage of the way that bone heals around Bicon implants, the CSL with Ti-mesh is a procedure that makes use of an external microfixated Ti-mesh as a means of stabilizing the implant within the graft.

Box 12-3 CSL quick guide

Recommended armamentarium

• Local anesthesia

• Scalpel with no. 15 blade

• Bibevel chisels

• Sinus lift osteotomes

• Sinus Lift Curette

• Hand Reamer

• 6.0-mm Bone Expander

• 1-mL syringe

• Bone-Graft Syringe

• SynthoGraft (0.25 to 1.50 g of 50- to 500-μm particle size)

• Periosteal elevator

• Cotton swabs

• Implant Inserter/Retriever with seating tip

• Bicon dental implant (5.0 × 6.0–mm implant recommended)

• Sinus Lift Abutment (recommended)

• Bicon Surgical Kit

Step-by-step procedure

1. Take preoperative radiographs to determine the extent of the defect.

2. Administer anesthesia.

3. Raise a buccally based full-thickness mucoperiosteal flap.

4. Score a rectangular window using thin bibeveled chisels.

5. With controlled, gentle movements, gently tap the rectangular window with a sinus lift osteotome until the window of bone is mobilized.

Briefly, a CSL procedure involves scoring the window’s outline through the use of chisels or piezotomes, taking great care to stay between 0.5 and 1 mm away from penetrating the floor, which minimizes the risk of tearing the sinus mucosal lining; the notched window is then gently fractured and vertically displaced into the sinus cavity while remaining tethered to the mucosal lining. The osteotomy is then sculpted using Hand Reamers and site expanders. When the osteotomy is completed, the implant should be able to make contact with a minimum of 1 to 2 mm of the buccal and palatal walls; together with the Sinus Lift Abutment, this should provide adequate stability for the implant. After introducing the bone-graft material and implants, the Sinus Lift Abutments can be placed into the implants to secure the assembly in place.

CSL procedure

A step-by-step quick guide for the CSL can be found in Box 12-3. The following treatment of a 66-year-old man illustrates the CSL procedure. After treatment of his moderate to advanced periodontal disease, which included the extraction of his maxillary molars and stabilization of his posterior occlusion (Fig 12-6a), implant treatment was initiated.

The first step was to obtain the appropriate radiographic studies (Figs 12-6b and 12-6c). After evaluating the radio-

6. Evaluate the palatobuccal span of the sinus cavity to ensure it is safe to proceed.

7. Using a Sinus Lift Curette, dissect the sinus mucosa away from the palatal and buccal walls.

8. Using Hand Reamers, widen the osteotomy to the final implant size. 9. Use the 6.0-mm Bone Expander to finalize the osteotomy and further elevate the sinus floor and crestal window unit.

9. Inspect the mucosa for any tears.

10. Using a 1-mL syringe, collect blood from the surgical site.

11. Slowly pour the SynthoGraft into the dappen dish and mix it with blood (obtained from surgical site or via venipuncture) using the periosteal elevator until it is completely wetted or has a putty-like consistency (autogenous bone may also be used).

12. Very slowly and gently, use the Bone-Graft Syringe to aspirate the SynthoGraft and blood mixture and inject it into the osteotomy.

13. Carefully press or tap the implant into the osteotomy using the Implant Inserter/Retriever until the implant’s shoulder is above the level of the crest.

14. Insert Sinus Lift Abutments.

15. Further seat the implant and Sinus Lift Abutment assembly into the crest.

16. Create a horizontal releasing incision to ensure tension-free closure over the Sinus Lift Abutments.

17. Suture the flap to conclude the procedure.

graphs, anesthesia was administered, followed by raising a buccally based full-thickness mucoperiosteal flap to expose the entire crestal expanse (Fig 12-6d). After the crest was exposed, thin bibevel chisels were used to score a rectangular window into the bone (Figs 12-6e and 12-6f). The dimensions of the rectangle should have a width less than the diameter of the intended implant and a length that is 4 to 5 mm more than the sum of the implant diameters (eg, two 5.0-mm implants would have a rectangle length of 14 to 15 mm).

The notched rectangle in the bone was gently tapped or compressed using sinus lift osteotomes until it yielded (Figs 12-6g and 12-6h). When mobilizing the outlined rectangle, all movements must be gradual, gentle, and controlled. Once the bone rectangle was mobilized, the internal palatobuccal dimensions of the cavity and window were examined (Fig 12-6i). Next, a Sinus Lift Curette was used to dissect the sinus mucosa away from the palatal and buccal walls; this assisted in the mobilization of the bony window and allowed for further assessment of the internal dimensions and morphology (Fig 12-6j).

The osteotomy was then prepared with Hand Reamers (Figs 12-6k and 12-6l). Because the width of the window in this case was approximately 5 mm, 5.0- and 6.0-mm Hand Reamers were used successively to expand the osteotomy. Hand Reamers were chosen because they can both expand and ream simultaneously. Because there was minimal bone contact and depth (about 3 to 4 mm), it was possible to go directly from the 5.0- to the 6.0-mm reamer size. The osteotomy was finalized with a 6.0-mm Bone Expander (Fig 12-6m). The Bone Expander was used to both expand the bone and elevate the sinus floor and crestal window as a unit while it remained tethered to the sinus mucosal lining; after finalizing the osteotomy, it was inspected for tears (Fig 12-6n). Fig 12-6 (a) Preoperative clinical appearance of a patient requiring a CSL procedure. Note the absence of inflammation and marked gingival recession. (b and c) Preoperative radiographs. (d) A buccally based full-thickness mucoperiosteal flap is raised to expose the entire crestal expanse. (e) Transverse section showing the use of a bibeveled chisel to score the crestal bone. (f) A rectangular window is outlined in the crest. (g and h) Sinus lift osteotomes are used to mobilize the outlined rectangular bone. (i) Clinical image of the cavity and the window. (j) A Sinus Lift Curette is used to dissect the sinus mucosa away from the palatal and buccal walls. (k and l) Both 5.0- and 6.0-mm Hand Reamers are used to expand the osteotomy. —>

Upon confirmation that the sinus mucosa was intact, SynthoGraft was mixed with blood from the surgical site and injected into the osteotomy with a Bone-Graft Syringe. The SynthoGraft acts as padding against the sharp edges of the implant and as a radiographic marker showing the containment and extent of the sinus lift graft (Figs 12-6o and 12-6p). After the SynthoGraft mixture was inserted, the implants were placed. Two 6.0 × 6.0–mm implants were placed using an Implant Inserter/Retriever instrument (Fig 12-6q). The Inserter/Retriever instrument was used because it provides greater control of the implant. To seat the implant, the Inserter/Retriever instrument was used to press or lightly tap the implant until it was placed up to its shoulder: This provided contact with the crestal cortex, which was sufficient to temporarily retain the implant (Figs 12-6r to 12-6t).

After the implants were initially seated, Sinus Lift Abutments were gently attached, and the implant/abutment assembly was seated further into the osteotomy, completing this phase of the procedure (Figs 12-6u to 12-6x). Subsequently, the Sinus Lift Abutments were pressed against the crest, acting as pedestal feet for the implants, ensuring Fig 12-6 (cont) (m) A 6-mm Bone Expander finalizing the preparation of an osteotomy. (n) After completing the osteotomy, the mucosa is inspected for any tears. (o and p) SynthoGraft is injected into the osteotomy with a Bone-Graft Syringe. (q) Implant is seated into the osteotomy with an Implant Inserter/Retriever instrument. (r) The implant is placed to a depth that leaves the shoulder of the implant exposed. (s) The second 6.0 × 6.0–mm implant is placed. (t) Clinical image of the initially seated implants to a depth that leaves the shoulder exposed; this allows contact with the crestal cortex, which provides sufficient friction to temporarily retain the implant. (u and v) Sinus Lift Abutments are placed into the implants. (w) The implant/abutment assembly is seated further into the osteotomy. (x) The Sinus Lift Abutment is tapped to seat the implant abutment assembly further into the osteotomy. (y) A horizontal releasing incision is made to ensure a tension-free closure over the Sinus Lift Abutments. (z and aa) A continuous suture secures the flap to conclude the surgical procedure. — Fig 12-6 (cont) (bb) Postoperative radiograph. (cc) One-month postoperative radiograph. Note the consolidation of the graft as it coalesces around the implants. (dd) Five-month postplacement radiograph. (ee) An IAC is placed. (ff) Clinical image of two IAC seated restorations. (gg) Postplacement radiograph. Note the newly consolidated sinus floor and the crestal bone’s adaptation to the hemispheric undersurface of the abutments.

their stability and positioning within the osteotomy. A horizontal releasing incision was made to ensure a tension-free closure over the Sinus Lift Abutments (Fig 12-6y). Finally, a continuous suture through the flap concluded the CSL procedure (Figs 12-6z to 12-6bb).

One month after placement, the graft was seen to be coalescing around the implants (Fig 12-6cc). Five months following the procedure, two IACs were placed (Figs 12-6dd and 12-6ee). Figures 12-6ff and 12-6gg show the restorations and radiograph, respectively. In the postplacement radiograph, the newly consolidated sinus floor and the crestal bone’s adaptation to the hemispheric undersurface of the abutments is apparent.

CSL with Ti-mesh procedure

When the native bone is 3.0 mm or less in height and the transverse distance between the palatal and buccal internal wall exceeds 6.0 mm, it is not possible to achieve friction between the walls of the osteotomy and the implant, which renders the Sinus Lift Abutment ineffective. To avoid the more intrusive lateral sinus lift, a CSL with Ti-mesh procedure may be pursued as an alternative modality.

A Ti-mesh may be used to enhance the CSL procedure. A piece of pliable, surgical-grade titanium 0.2 mm thick is trimmed so that it can overlap the window in at least one dimension, which is typically buccopalatally by at least 8 to 10 mm. After the mesh is trimmed to lay 2.0 mm above the implant shoulder and affixed to a black Healing Plug, the bony window is mobilized vertically, and bone-graft particles are placed into the resulting cavity. The implant can be introduced, but it should be kept above the crest until the black Healing Plug and Ti-mesh assembly is placed into its well. The implant is then fully seated, and the Ti-mesh intimately adapted and burnished onto the crest, with the sides of the mesh secured to the bony crest with tacks or self-tapping microfixation screws.

The following treatment illustrates the CSL with Ti-mesh procedure. A step-by-step quick guide for the CSL can be found in Box 12-4. A 59-year-old woman with a long history of edentulism presented with a hypertrophic left maxillary sinus. The sinus floor had less than 2.0 mm of native bone at the crest. With another implant design, this treatment would have required a lateral sinus lift; however, because of the short length of Bicon implants, a CSL with Ti-mesh could be readily performed.

Box 12-4 CSL with Ti-mesh quick guide

Recommended armamentarium

• Local anesthesia

• Scalpel with no. 15 blade

• 1-mL syringe

• Bone scraper

• Ti-mesh (2 mm thick, 1-mm perforations)

• Straight chisels

• Curved Chisels

• Sinus lift osteotomes

• Blunt Sinus Lift Curette

• Hand Reamer

• 6.0-mm Bone Expander

• 1.2-mm self-tapping low-profile screw

• 3.0-mm tacks or 4.5-mm self-tapping screws

• Bone-Graft Syringe

• SynthoGraft (0.25 to 1.50 g of 50- to 500-μm particle size)

• Periosteal elevator

• Cotton swabs

• Implant Inserter/Retriever with seating tip

• Bicon dental implant (5.0 × 6.0–mm implant recommended)

• Sinus Lift Abutment (recommended)

• Bicon Surgical Kit

Step-by-step procedure

1. Take preoperative radiographs to determine the extent of the defect.

2. Administer anesthesia.

3. Raise a buccally based full-thickness mucoperiosteal flap to expose the crest.

4. Collect a small amount of blood (approximately 0.5 mL) with the 1-mL syringe.

5. Using a bone scraper, flatten and thin the crest and save the bone scrapings in the dappen dish.

6. Measure the crestal dimensions to aid in the preliminary design of the Ti-mesh.

7. Trim the Ti-mesh.

The necessary imaging studies revealed hypertrophic bone and an enlarged sinus cavity (Figs 12-7a and 12-7b). The images revealed that the contact with the walls would be insufficient to support an implant; therefore, another means of stabilization would be necessary if implants were to be placed at the same time as the sinus lift (Fig 12-7c). After administering anesthesia, a papilla-sparing incision was made to produce a buccally based full-thickness mucoperiosteal flap (Fig 12-7d). Blood was obtained from the surgical site and saved for later use as a wetting agent for SynthoGraft (Fig 12-7e). After the crest was exposed, the bone was flattened and thinned with a bone scraper (Fig 12-7f). The use of a bone scraper on the crest allowed for better control during the mobilization of the crestal window.

Next, rough measurements of the ridge were obtained and used for the preliminary design and trimming of the

8. Place the Ti-mesh over the ridge and bend it to conform its shape to the intended site.

9. Store the Ti-mesh in a sterile container.

10. Using Curved Chisels and straight chisels, score the outline of a crestal window

11. Using the 4.0-mm sinus lift osteotome, fracture the crestal window along the scored outline and mobilize the window vertically.

12. Carefully separate the sinus mucosal lining from the internal walls with a blunt Sinus Lift Curette.

13. Prepare the osteotomy using the Hand Reamers.

14. Finalize the osteotomy using the Bone Expander.

15. Retrieve the implant from its packaging by holding the black Healing Plug.

16. Trim the black Healing Plug, leaving 2 mm of material above the shoulder of the implant.

17. Secure the black Healing Plug to the center of the Ti-mesh with a 1.2-mm self-tapping low-profile screw.

18. Slowly pour the SynthoGraft into the dappen dish and mix it with blood (obtained earlier in the 1-mL syringe) using the periosteal elevator until it is completely wetted or has a putty-like consistency (autogenous bone may also be used).

19. Very slowly and gently, use the Bone-Graft Syringe to aspirate the SynthoGraft and blood mixture and inject it into the osteotomy.

20. Using the Bone Expanders, pack the graft and lift the sinus floor to make room for the implant.

21. Place the bone scrapings in the osteotomy.

22. Using the Implant Inserter/Retriever, insert the implants into the osteotomy.

23. Disengage the Inserter/Retriever once the implant contacts the edge of the crestal window.

24. Insert the Healing Plug with Ti-mesh into the well of the implant.

25. Secure the Ti-mesh to the buccal and palatal plates using 3.0-mm tacks or 4.5-mm self-tapping screws.

26. Create a horizontal releasing incision to ensure tension-free closure over the Sinus Lift Abutments.

27. Suture the flap to conclude the procedure.

Ti-mesh (Fig 12-7g). The Ti-mesh was trimmed and placed over the ridge (Figs 12-7h and 12-7i). After the Ti-mesh was molded to fit over its intended location, it was stored in a sterile container.

Subsequently, the crestal window was created using Curved Chisels and straight chisels (Figs 12-7j and 12-7k). For this patient, the width of the window was kept at 4.5 mm because a 5.0-mm implant was planned; the length of the widow should be long enough to permit convenient access. The crestal window was fractured along the scored lines with a 4.0-mm sinus lift osteotome and slightly mobilized vertically (Fig 12-7l).

Following the mobilization of the window, the sinus mucosal lining was carefully separated from the internal walls with a blunt Sinus Lift Curette; this allowed for further mobilization of the bony window (Fig 12-7m). The osteotomy was then prepared with the successive use of increasingly wider-diameter Hand Reamers, followed by the use of a 5.0-mm Bone Expander (Figs 12-7n to 12-7p). Fig 12-7 (a) The preoperative periapical radiograph with measurements reveals a severely hypertrophic sinus. (b) CBCT study shows the large internal buccopalatal dimension of the sinus cavity. (c) Enhanced view of the internal buccopalatal dimension of the sinus cavity. Measurements demonstrate that the implant will not be able to contact the walls. (d) A buccally based full-thickness mucoperiosteal flap is made with a papilla-sparing incision. The patient’s adjacent IAC was removed to improve visibility. (e) Blood is obtained for use as a wetting agent for SynthoGraft. (f) A bone scraper is used to flatten and thin the crestal bone. (g) A periodontal probe is used to measure the crestal bone to facilitate the trimming of the Ti-mesh.

After removing the implant from its packaging, its Healing Plug was cut so that 2.0 mm of material remained above the shoulder of the implant (Fig 12-7q). The plug was then secured to the center of the Ti-mesh with a 1.2-mm self-tapping low-profile screw (Fig 12-7r). Subsequent to the assembly of the Ti-mesh and black Healing Plug, a SynthoGraft mixture was prepared using the blood obtained earlier. As in the standard CSL procedure, the SynthoGraft mixture served as a cushion to protect the sinus mucosa from the advancing implant and acted as a radiographic marker for the extent of the sinus lift and its containment (Figs 12-7s and 12-7t). After injecting the SynthoGraft into the newly formed space, Bone Expanders were used to pack the graft and further elevate the sinus floor. The crestal bone scrapings and SynthoGraft were packed over the osteotomy, and the implant was placed with an Implant Inserter/Retriever instrument (Figs 12-7u to 12-7y). Fig 12-7 (cont) (h) The Ti-mesh is placed over the crest and bent to adapt to its intended site. (i) Graphic illustration of the Ti-mesh and Healing Abutment assembly. (j) A Curved Chisel is used to score the alveolar ridge. (k) A straight chisel is used to make the final edge cut of the rectangular window. (l) The crestal window is inwardly fractured with a 4.0-mm sinus lift osteotome and mobilized vertically. (m) A blunt Sinus Lift Curette is used to separate the sinus mucosal lining from the internal sinus wall. (n and o) Both 4.5- and 5.0-mm Hand Reamers are used to expand the osteotomy. (p) A 5.0-mm Bone Expander is used to finalize the osteotomy. ——_>

When the implant’s shoulder contacted the edge of the crestal window, it was disengaged from the Inserter/Retriever instrument and the Ti-mesh, and black plug assembly (see Fig 12-7i) was inserted into the well of the implant (Figs 12-7z and 12-7aa). The Ti-mesh was then secured to the buccal and palatal plates of the alveolar bone using a 4.5-mm self-tapping screw (Figs 12-7bb and 12-7cc). Alternatively, 3.0-mm tacks could have been used. The tacks or screws immobilize the implant and secure it in its proper location, orientation, and depth. To conclude the procedure,

a horizontal releasing incision was necessary to ensure tension-free closure (Fig 12-7dd). Finally, the flap was closed with continuous sutures (Figs 12-7ee to 12-7ii).

After 9 weeks of healing, the Ti-mesh was removed, and the soft tissues were allowed to heal further (Fig 12-7jj). A polyetheretherketone (PEEK) Healing Abutment was placed at the uncovering to assist in the formation of the implant’s soft tissue sulcus prior to receiving the permanent IAC (Fig 12-7kk). However, abutment choice and definitive restoration is ultimately up to the clinician. Figures 12-7ll and 12-7mm show periapical radiographs at the time of placement of the IAC and at an 18-month follow-up, respectively. Fig 12-7 (cont) (q) The black Healing Plug is trimmed 2.0 mm above the implant shoulder. (r) The black Healing Plug is attached to the Ti-mesh with a 1.2-mm selftapping low-profile screw. (s and t) SynthoGraft is injected into the osteotomy with the Bone-Graft Syringe. (u) A 5.0-mm Bone Expander is used to pack the SynthoGraft material, which will raise the sinus floor while creating a space for the implant. (v) Appearance of the packed SynthoGraft. (w) Bone shavings are placed into the osteotomy. (x and y) The implant is initially seated using the Implant Inserter/Retriever instrument. (z and aa) The Ti-mesh and the black Healing Plug assembly is inserted into the well of the implant. (bb and cc) The Ti-mesh is secured to the buccal and palatal plates of the alveolar bone with 3.0-mm tacks. (dd) A horizontal releasing incision is made to ensure tension-free closure. —> Fig 12-7 (cont) (ee and ff) The flap is closed with continuous sutures, and the IAC of the adjacent premolar is reinserted. (gg to ii) Postoperative periapical radiographic and facial and palatal CBCT images reveal the appropriate positioning of the implant and the successful containment of the graft, suggesting the absence of mucosal perforations. (jj) Six-month follow-up radiograph without the Ti-mesh membrane, which was removed 4 months previously. (kk) A PEEK Healing Abutment is inserted into the well of the implant to facilitate the formation of the mucosal sulcus prior to placement of the IAC restoration. (ll) Postoperative radiograph of the IAC restorations. (mm) Eighteen-month postoperative radiograph.

Lateral Sinus Lift Techniques

After the advent of the early crestal window, which is also known as the Summers technique, Engelke et al[12] reported on a minimally invasive lateral sinus lift approach, also known as the subantroscopic laterobasal sinus floor augmentation (SALSA). Since their report, there has been continuous debate as to which sinus lift technique is superior (ie, Engelke versus Summers); the literature is not helpful, as some authors report fewer implant losses with the crestal approach, while others recommend the lateral approach only in cases of less than 4.0 mm bone height.[13–15] The choice of a sinus lift procedure is a function of the type of implant as well as the available bone height and skill of the clinician (see Fig 12-1 and Table 12-1). Since the introduction of Bicon’s 5.0-mm implants, most surgeons no longer perform lateral sinus lift procedures except in extreme conditions. When using short implants in the maxilla with less than 1.0 mm of alveolar bone height or where it is advisable to avoid surgical manipulation of the alveolar crest, augmentation of the alveolar crest can be achieved by performing a lateral sinus lift (LSL).

Box 12-5 LSL procedure quick guide

Recommended armamentarium

• Local anesthesia

• Scalpel with no. 15c blade

• Dappen dish

• Rotary instruments (or piezosurgical instruments)

• 1-mL syringe

• Resorbable collagen barrier membrane

• 2.0-mm pilot drill

• Latch Reamers

• Bone-Graft Syringe

• 2.0- to 5.0-mm sinus lift osteotomes

• 2.0- to 5.0-mm round surgical carbide burs

• 2.0- to 5.0-mm diamond burs

• Sinus mucosa elevating instruments (Kirsch)

• SynthoGraft (0.25 to 1.50 g of 50- to 500-μm particle size)

• Implant Inserter/Retriever with seating tip

• Bicon dental implant (5.0 × 6.0–mm implant recommended)

• Sinus Lift Abutment (recommended)

• Bicon Surgical Kit

Step-by-step procedure

1. Perform the necessary radiographic studies to determine the extent of the defect.

2. Administer anesthesia.

3. Raise a mucoperiosteal flap to expose the lateral aspect of the crest.

4. With rotary instruments, prepare a bone trough that is 4.0- to 5.0mm wide, with 10 mm of length for each implant (eg, two implants would require 20 mm).

5. Collect any autogenous bone particles in the dappen dish.

6. Using a 1-mL syringe, collect blood from the surgical site.

7. Slowly pour the SynthoGraft into the dappen dish and mix it with blood (obtained from surgical site or via venipuncture) using the periosteal elevator until it is completely wetted or has a putty-like consistency (autogenous bone may also be used).

8. Elevate the sinus mucosa.

9. Using the Bone-Graft Syringe, fill the void that results from elevating the mucosa with the SynthoGraft and blood mixture.

10. Use the 2.0-mm pilot drill to initiate the osteotomy.

11. Using the Latch Reamers, begin to widen the osteotomy to the final implant diameter by sequentially increasing reamer diameters, and save any collected bone in a dappen dish for later use.

12. Insert collected bone into the osteotomy.

13. Place the implant into the osteotomy with the provisional Sinus Lift Abutment, ensuring the coronal part of the implant rests 2 mm below the alveolar crest.

14. Suture the flap to conclude the procedure.

LSL procedure

A step-by-step quick guide for the LSL can be found in Box 12-5. The following patient treatment demonstrates an LSL procedure. Similar to the ISL and CSL procedures, the first step in the LSL is a careful evaluation of preoperative radiographic images (Figs 12-8a to 12-8c). In rare cases when the maxilla’s dorsal aspect must be determined, a cephalometric radiograph is recommended (Fig 12-8d). Fig 12-8 (cont) (c) Reformatted panoramic view (section) of a CT scan, showing the left maxillary sinus and a maxillary sinus septum. (d) Section of the cephalometric radiograph ( yellow dots indicate the most ventral points in the maxilla and mandible; the atrophy of the maxillary bone is increased because of the residual dentition in the mandible, which is known as the combination syndrome). (Reprinted with permission from Ewers.[9] )

In the following treatment, a 36-year-old man presented with missing maxillary left premolars; a panoramic radiograph revealed minimal crestal bone with less than 1 mm of bone in the position of the maxillary left second premolar (Fig 12-9a). To begin the procedure, a mucoperiosteal flap was raised, exposing the lateral aspect of the alveolar crest (Fig 12-9b). With the use of a surgical carbide bur, followed by a diamond bur, a bone trough was prepared[16] (Figs 12-9c and 12-9d). Alternatively, piezoelectric surgical burs could have been used. For a single implant, the trough should be approximately 4 to 5 mm wide and 10 mm long; two implants require a trough to be roughly 20 mm long. The trough should be located directly at the lateral lower edge of the floor of the maxillary sinus. As the trough was prepared, the sinus mucosa became visible (Figs 12-9e and 12-9f). The bone trough that is created for the LSL procedure is particularly effective if the maxillary sinus needs to be dissected away from the septa of the sinus[17] (Fig 12-9g). While making the trough, any small bone chips should be collected in a dappen dish for future use as a grafting material.[18]

Prepare a SynthoGraft mixture by slowly pouring SynthoGraft into a dappen dish and mixing it with blood collected via a 1.0-mL syringe from the surgical site. Once the SynthoGraft and blood mixture is prepared, carefully elevate the sinus mucosa and fill the resulting cavity with bone-graft material (Figs 12-9h to 12-9k). The efficacy of this procedure is enhanced when the mucosa is dissected away from the septa of the maxillary sinus.[17]

Next, the osteotomy was initiated with the 2.0-mm pilot drill. The bone-grafting material acted as a buffer, which prevented damaging the sinus mucosa with the pilot bur (Figs 12-9l to 12-9n). Osteotomies were then prepared in the position of the maxillary left first and second premolar. Because the sinus mucosa was elevated via the bone-graft material, the chance of perforating the membrane was reduced, which is one of the major advantages of using the lateral approach. Following the use of the pilot drill, the osteotomy was expanded by using Latch and Hand Reamers with sequentially increasing diameters (Fig 12-9o to 12-9q). Bone collected in the flutes of the reamers was saved in a dappen dish for later use. The bone was very soft, so great care was taken in its collection (Fig 12-9r). Fig 12-9 (a) Preoperative radiograph of a 36-year-old man with missing left maxillary premolars. Alveolar bone is less than 2 mm at the position of the maxillary first premolar. (b) Illustration showing a preoperative crest with a vertical residual bone height of 1 to 3 mm and a cut through the mucosa and periosteum in the middle of the crest. (c and d) A bone trough is prepared with a round surgical carbide bur. (e) A diamond bur is used to prepare a bone trough. (f) Illustration depicting correct location of the bone trough. (g) Clinical appearance of bone trough without a mucosal perforation. (h) The elevation of the maxillary sinus mucosa is shown after being dissected away from the sinus septum. —_> Fig 12-9 (cont) (i and j) The maxillary sinus mucosa is elevated with a Sinus Lift Curette. (k) Bone-graft material is injected into the cavity with a Bone-Graft Syringe. (l) The alveolar recess below the sinus mucosa is completely filled with the graft material. (m and n) The osteotomy is initiated with the 2.0-mm pilot drill. (o and p) The second osteotomy is initiated at the position of the maxillary left first premolar. A Hand Reamer is used to widen the osteotomy. (q) Final appearance of the osteotomies prior to placement of the implants. (r) Collected autogenous bone from the Hand Reamers on a periosteal elevator. (s) Autogenous bone is inserted into the osteotomy. (t) The first 4.0 × 5.0–mm implant is placed into the position of the left maxillary second premolar. —>

Once the osteotomy had been prepared, it was filled with bone collected from the Latch and Hand Reamers, into which the implant was placed (Figs 12-9s to 12-9u). The black Healing Plug was inserted into the implant and covered with the harvested bone (Figs 12-9v and 12-9w). As the autogenous bone was pressed with the bone-graft material, the surface of the Bicon implant became completely covered with bone. Because the trough was small, it was not necessary to cover the bone-graft material with a membrane. If perforation of the mucosa were observed, it would have been advisable to place a resorbable collagen membrane.[19] Fig 12-9 (cont) (u) Clinical view of seated implants in their osteotomies. (v) Clinical image of seated implants after their polyethylene black Healing Plugs were cut. (w) Implant with Healing Plug covered with harvested bone. (x) Clinical image of a split-thickness flap, which allows for a double closure via a pedicled periosteal flap. (y and z) Clinical image and illustration of a double closure flap with a single-knot resorbable suture. (aa and bb) If the dimensions of the osteotomy walls do not provide stability for the implant, a Sinus Lift Abutment can be placed. (cc) Postoperative radiograph. (dd) Postoperative image of two IAC restorations. (ee) Two-year postoperative radiograph.

An envelope flap was reflected to provide a double-layer closure via a pedicled periosteal flap (Fig 12-9x) and subsequently a second-layer closure with a single-knot resorbable suture (Figs 12-9y and 12-9z). If the remaining cortical bone were very thin and the stability of the implant’s position were uncertain, a Sinus Lift Abutment may have been used (Figs 12-9aa and 12-9bb). To prevent the risk of pressing the bone-grafting material into the vestibulum, patients should be instructed not to blow their nose. Figures 12-9cc to 12-9ee show the postoperative radiographs and clinical images.

Fig 12-10 (a) Postoperative radiograph following an LSL and bone graft in the alveolar recess with a “hood” over the implant, which is seen as a hallmark of a successful LSL procedure. (b) Five-month postoperative radiograph revealing newly formed bone. A major benefit of the LSL is the direct visualization it provides of the maxillary sinus septum and sinus mucosa, which is not possible from the typical CSL procedure. A hallmark of a successful LSL procedure is the appearance of a “hood,” observable in postoperative radiographs (Fig 12-10a). If performed correctly, the LSL should yield bone after a few months (Fig 12-10b). LSL procedures may also be used for patients in whom morphology or injury has rendered less invasive procedures impossible.

Management of benign sinus lesion followed by LSL

As mentioned earlier in this chapter, patients should be assessed for any pathology, developmental disorder, or other injury that would contraindicate sinus surgery. When an injury or another disorder is present, and less invasive procedures such as ISL and CSL cannot be pursued, then LSL presents an alternative treatment option to provide adequate bone volume for implant placement.

The following describes the treatment of a large mucous retention cyst. Despite being asymptomatic, these cysts must be treated prior to attempting a sinus lift because their volume and weight could affect the mechanical stability of a graft or an implant. A step-by-step quick guide showing the management of these lesions, followed by LSL, can be found in Box 12-6.

A 55-year-old woman presented with missing maxillary right molars, sinus hypertrophy, and a dome-like radiopacity that measured over 25 mm in height above the sinus floor (Figs 12-11a and 12-11b). Depending on the extent of the defect, alternative therapies may be considered (the patient in this example was referred to otolaryngology for conservative treatments, which showed minimal changes in the size of the lesion after 3 months) (Fig 12-11c). After administering a local anesthetic, the patient’s lip was retracted to expose the surgical site. A full-thickness flap was reflected to expose the lateral wall of the sinus. Using a Shepherd bur at high speed with copious irrigation, an antrostomy was prepared on the lateral wall of the sinus (Caldwell-Luc approach) (Fig 12-11d). After fracturing the window, the sinus wall was breached, and the contents of the sinus were allowed to evacuate (Fig 12-11e). The site was then closed and allowed to heal for 3 months (Fig 12-11f).

Following the healing period, the LSL phase of the procedure was initiated: After the incision and initial elevation of the flap, it became necessary to separate the adhesion of the sinus mucosa from the buccal soft tissues, which was achieved by sharp dissection (Fig 12-11g). By dissecting the adhesion, some of the buccal soft tissue became incorporated as part of the sinus mucosal lining (Fig 12-11h). Next, the lateral wall of the opening was carefully widened using a Kerrison rongeur (Figs 12-11i and 12-11j). As shown in this treatment, during the dissection of the mucosal lining, small tears may occur; these tears can be easily repaired using hemostatic agents (Figs 12-11k and 12-11l). To prepare the bone-graft mixture, SynthoGraft was mixed with the patient’s blood. The SynthoGraft and blood mixture was then carefully injected into the sinus cavity (Fig 12-11m). A resorbable collagen barrier membrane was positioned over the graft and window before closing the flap, allowing the site to heal (Figs 12-11n to 12-11r).

The final phase of the procedure was implant placement. The osteotomies were initiated using a 2.0-mm pilot drill and were widened with Latch and Hand Reamers (Figs 12-11s and 12-11t). Using the Implant Inserter/Retriever instrument, the implants were placed as described above (Figs 12-11u to 12-11x). The site was closed, concluding the procedure (Figs 12-11y and 12-11z).

Box 12-6 Management of a benign sinus lesion with LSL quick guide

Recommended armamentarium

• Local anesthesia

• Scalpel with no. 15 blade

• Shepherd bur

• Kerrison rongeur

• Dappen dish

• Resorbable collagen barrier membrane

• 2.0-mm pilot drill

• Latch Reamers

• Hand Reamers (threaded straight handle)

• 4.0-mm Osteotome (optional)

• Bone-Graft Syringe (optional)

• SynthoGraft (0.25 to 1.50 g of 50- to 500-μm particle size)

• Periosteal elevator

• Cotton swabs

• Implant Inserter/Retriever (with seating tip)

• Bicon dental implant (5.0 × 6.0–mm implant recommended)

• Sinus Lift Abutment (recommended)

• Bicon Surgical Kit

Step-by-step procedure

1. Take preoperative radiograph to determine the extent of the defect.

2. Attempt alternative conservative therapies (optional).

3. Administer anesthesia.

4. Retract the lip and expose the surgical site.

5. Create a full-thickness flap that exposes the lateral wall of the sinus (avoid the roots of adjacent teeth).

6. Using a Shepherd bur at high speed with copious irrigation, create an antrostomy on lateral wall of the sinus (Caldwell-Luc approach).

7. Breach the sinus wall and allow evacuation of contents (eg, infection, blood, pus).

8. Irrigate the surgical site and sinus cavity, then suture the site closed.

9. Create a full-thickness flap that exposes the antrostomy.

10. Dissect the sinus mucosa away from the buccal soft tissues.

11. Using a Kerrison rongeur, carefully widen the opening of the lateral wall antrostomy.

12. Patch any tears to the mucosal lining with Surgicel (optional).

13. Slowly pour the SynthoGraft into the dappen dish, and mix it with blood (obtained from surgical site or via venipuncture) using the periosteal elevator until it is completely wetted or has a putty-like consistency.

14. Pack the SynthoGraft and blood mixture into the sinus cavity.

15. Position a resorbable collagen barrier membrane over the graft and window.

16. Close the flap.

17. Allow the site to heal (4 to 6 months).

18. Take a preoperative radiograph to asses the sinus lift and bone graft.

19. Using the 2.0-mm pilot drill, mark the location of the future osteotomy by drilling through the cortical bone of the alveolar crest.

  - **Important:** Stop drilling before perforating the sinus floor. 

21. Using the Latch Reamers, begin to widen the osteotomy to the final implant diameter by sequentially increasing reamer diameters.

22. Using the Hand Reamers (straight handle), widen the osteotomy to the final implant diameter by sequentially increasing reamer diameters.

23. Place the implant into the osteotomy using the Implant Inserter/ Retriever, ensuring that when finally seated, the coronal part of the implant rests 2.0 mm below the alveolar crest.

24. Verify the angle of the implants with guide pins.

25. Disengage the Implant Inserter/Retriever.

26. Insert either a black Healing Plug or a Sinus Lift Abutment into the implant with its wider side oriented buccolingually, and gently tap it into place.

27. Suture the flap to conclude the procedure.

28. Allow the site to heal (2 to 4 months). Fig 12-11 (a) Initial radiograph with well-defined radiopacity above the location of the maxillary right molars. (b) Radiograph shows the extent of the lesion. (c) Initial conservative therapy resulted in minimal change in the size of the lesion, as seen in this radiograph, which was taken 3 months after the initial radiographs and conservative treatment. Fig 12-11 (cont) (d) An antrostomy is created on the lateral wall of the sinus using a Shepherd bur at high speed with copious irrigation (Caldwell-Luc approach). (e) The sinus wall and membrane are breached, allowing the evacuation of the lesion’s contents. The site and sinus were then thoroughly irrigated and closed. (f) Panoramic radiograph taken after 3 months of healing. (g) A lateral sinus lift approach is started. After the incision and initial elevation of the flap, it became necessary to separate the adhesion of the sinus mucosa to the buccal soft tissues. This is achieved by sharp dissection. (h) The sharp dissection of the adhesion allows some of the buccal soft tissue to become incorporated as part of the sinus mucosal lining. (i) A Kerrison rongeur is used to carefully widen the opening of the lateral wall, which was created during the Caldwell-Luc procedure. (j) Several small bites provided a significantly wider opening. (k) During the dissection of the mucosal lining, a tear is encountered at the distal edge of the opening. (l) The tear is easily patched using a blood-clot-inducing material (hemostatic agent). (m) The thoroughly mixed SynthoGraft particles and blood obtained from the surgical site and via a venipuncture are carefully injected and packed into the sinus cavity. (n) A resorbable collagen barrier membrane is positioned over the graft and window before closing the flap. (o) Postoperative radiograph. (p) Two-week postoperative radiograph. Fig 12-11 (cont) (q and r) Five-month postoperative radiographs. (s and t) Implant osteotomies are prepared. A pilot drill is used to initiate an osteotomy, and the osteotomy is widened with sequentially wider Hand and Latch Reamers until two 6.0-mm-wide osteotomies are achieved. (u and v) An implant is inserted with an Implant Inserter/Retriever instrument. (w) Trajectories of the implants are confirmed with two guide pins seated in the wells of the implants. If necessary, slight adjustments could be made by moving the guide pins. (x) A black Healing Plug is inserted into the well of an implant. (y) Postoperative radiograph. (z) Two-year postoperative radiograph.

Conclusion

The Bicon implant system with short implants possesses characteristics that have dramatically decreased the need for sinus lift procedures; however, there are still some atrophic maxillary arches where even the shortest of implants will not suffice. Lack of adequate bone height is frequently encountered in the clinical setting, especially following long periods of edentulism; therefore, clinicians should become familiar with the procedures outlined in this chapter so they will be prepared when confronted with minimal alveolar bone volume.

This chapter has provided detailed instructions on internal sinus lift procedures, crestal sinus lifts—including an ISL/crestal window hybrid procedure—and lateral sinus lifts. The techniques discussed in this chapter should prove indispensable for clinicians wishing to perform sinus lifts in conjunction with placing Bicon implants.

References

1. Tatum OH. Lecture presented to the Alabama Implant Congress. Alabama Implant Congress 1976.

2. Boyne PJ, James RA. Grafting of the maxillary sinus floor with autogenous marrow and bone. J Oral Surg 1980;38:613–616.

3. Mellonig JT, Bowers GM, Bailey RC. Comparison of bone graft materials. Part I. New bone formation with autografts and allografts determined by Strontium-85. J Periodontol 1981;52:291–296.

4. Tatum H. Maxillary and sinus implant reconstructions. Dent Clin North Am 1986;30:207–229.

5. Summers RB. A new concept in maxillary implant surgery: The osteotome technique. Compendium 1994;15:152–154.

6. Summers RB. The osteotome technique: Part 3: Less invasive methods of elevating the sinus floor. Compendium 1994;15:698–710.

7. Ali SA, Karthigeyan S, Deivanai M, Kumar A. Implant rehabilitation for atrophic maxilla: A review. J Indian Prosthodont Soc 2014;14:196–207.

8. Ewers R. Maxilla sinus grafting with marine algae derived bone forming material: A clinical report of long-term results. J Oral Maxillofac Surg 2005;63:1712–1723.

9. Ewers R. Implant surgery. In: Lambrecht JT. Oral and Implant Surgery: Principles and Procedures. Chicago: Quintessence, 2009.

10. Karabuda C, Arisan V, Ozyuvaci H. Effects of sinus membrane perforations on the success of dental implants placed in the augmented sinus. J Periodontol 2006;77:1991–1997.

11. Pikos MA. Maxillary sinus membrane repair: Report of a technique for large perforations. Implant Dent 1999;8:29–34.

12. Engelke W, Schwarzwäller W, Behnsen A, Jacobs HG. Subantroscopic laterobasal sinus floor augmentation (SALSA): An up-to-5-year clinical study. Int J Oral Maxillofac Implants 2003;18:135–143.

13. Zitzmann NU, Schärer P. Sinus elevation procedures in the resorbed posterior maxilla. Comparison of the crestal and lateral approaches. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;85:8–17.

14. Felice P, Pistilli R, Piattelli M, Soardi E, Barausse C, Esposito M. 1-stage versus 2-stage lateral sinus lift procedures: 1-year post-loading results of a multicentre randomised controlled trial. Eur J Oral Implantol 2014;7:65–75.

15. Pal US, Sharma NK, Singh RK, et al. Direct vs. indirect sinus lift procedure: A comparison. Natl J Maxillofac Surg 2012;3:31–37.

16. Vercellotti T. Essentials in Piezosurgery. Quintessence, 2009.

17. Zuckerkandl E. Zur Morphologie Des Gesichtsschädels. Stuttgart: Ferdinand Enke, 1877.

18. Lambrecht JT, Glaser B, Meyer J. Bacterial contamination of filtered intraoral bone chips. Int J Oral Maxillofac Surg 2006;35:996–1000.

19. Chung KM, Salkin LM, Stein MD, Freedman AL. Clinical evaluation of a biodegradable collagen membrane in guided tissue regeneration. J Periodontol 1990;61:732–736.

13

Ridge Splitting and the Split-Thickness Flap

Shadi Daher | Rolf Ewers | Andrea Cicconetti

The alveolar process is the part of the maxillary and mandibular bone whose function is to house and support the dentition. The pattern of osseous remodeling of maxillary and mandibular alveoli is well known. The loss of teeth, regardless of the cause, precipitates atrophy of the alveolar processes with a collapse of the buccal plate of the alveolus toward its palatal or lingual plate. The process of collapse initially spares the height of the alveolus; however, if there is a continuing absence of loading and stimulation, the entire alveolus will give way to the relentless process of atrophy over time.[1] The loss of both the buccal and lingual or palatal plates results in a loss of height and severe “saddle” deformities, leaving the patient with few options for restoring the dentition or reestablishing a stable chewing apparatus.

There are a number of methods to augment both the width and height of a deficient alveolar ridge, including but not limited to ridge splitting, cortical grafting, guided bone regeneration, and distraction osteogenesis. This chapter primarily examines the process of expanding the alveolar ridge with a variety of ridge-splitting techniques, as well as using a variation of cortical grafting to manage narrow ridges when combined with severe vertical and horizontal defects. The four surgical approaches include:

1. Ridge splitting using a full-thickness flap with minimal reflection

2. Ridge splitting using a buccal bone window in two stages

3. Ridge splitting using a split-thickness flap

4. Ridge reconstruction using screw-retained cortical grafts

Ridge-Splitting Procedure Prerequisites

Thin maxillary alveolar crest

To be viable in either alveolus, ridge-splitting procedures must satisfy the following prerequisites.

First, the ridge must have sufficient height to accommodate the placement of the chosen implant at a depth of 2 to 3 mm below the bony crest, while still leaving a safe distance from any vital structure (eg, maxillary sinus or nasal floor). When making these calculations, clinicians must be cognizant of the fact that the splitting procedure, as well as the healing of the two cortices, is akin to the healing of the edge of an extraction socket; in either case, minor loss of bone height should be expected. Therefore, it is advisable to place an implant 1 to 2 mm deeper than the standard recommended depth.

The second prerequisite is the availability of a sufficiently wide basal bone within 8 to 10 mm from the top of the crest to receive the apex of the implant. Even 1 or 2 mm of engagement with this basal bone will provide the stability that a Bicon implant needs to facilitate osseointegration.

Finally, there must be distinct buccal and lingual or palatal cortical plates encasing an intervening layer of cancellous bone to ensure the presence of adequate endosseous circulation and facilitate the separation of the plates.

Mandibular alveolar crest

The conditions are somewhat different in the mandible, where the alveolar process has a generally thicker lingual cortex and a relatively inflexible, thick buccal plate, especially at its basal area where the alveolar process transitions into its basal, long-bone component. As with the maxillary ridge expansion, there are three prerequisites that dictate the selection of a mandibular ridge-splitting procedure.

First, the alveolus must accommodate an implant at a safe distance from the inferior alveolar nerve and mental foramen. Second, the height of the basal bone above the mandibular canal and mental foramen must allow for the secure engagement of the implant’s apex, which is 1 to 2 mm beyond the depth of the split bone. Third, the alveolus must have a core of identifiable cancellous bone to provide a blood supply and facilitate the propagation of a fracture, where necessary, and to split the ridge and allow for its expansion.

The alveolar bone’s inherent elasticity and compressibility allow for its expansion; therefore, when there is only a need for an additional 1 to 2 mm of width, it is possible to achieve the expansion with the standard Bicon protocols using a minor crestal graft without causing a fracture of the cancellous component (see chapter 19). The treatments presented in this chapter are limited to those that require significantly more than 2 mm of expansion.

Ridge Splitting with a Full-Thickness Flap

Treatment 1

In the first treatment, a 61-year-old woman presented with long-term maxillary edentulism, denture use, hypertrophic sinuses, and a thin alveolus in the maxillary anterior sextant. The proposed plan of treatment included bilateral sinus lifts in the posterior sextants and ridge expansion in the anterior sextant, followed by implant placements in all sites, to restore a first molar occlusion with Integrated Abutment Crowns (IACs).

The pretreatment analysis revealed an edentulous maxilla with an irregular alveolus and an ill-fitting complete denture (Fig 13-1a). The preoperative panoramic radiograph revealed marked sinus hypertrophy, particularly on the left side, and adequate height of the alveolar crest in the anterior sextant, satisfying one of the prerequisites for using the ridge-splitting procedure (Fig 13-1b).

The preplacement radiograph shows the healing of the left lateral sinus lift graft (Fig 13-1c). The cone beam computed tomography (CBCT) scan of the maxillary anterior sextant reveals a knife-edge configuration of the crest with over 14 mm of height, the availability of wide basal bone within 10 mm of the crest, and the presence of cancellous bone between the distinct labial and palatal cortical plates (Figs 13-1d and 13-1e). These findings satisfied all of the prerequisites for a ridge-splitting procedure. The pretreatment planning also included the fabrication of a palatal guide based on the patient’s existing denture (Fig 13-1f).

The initial incision exposed only the crestal-most aspect of the alveolus to minimize any interruption of the periosteal blood supply to the buccal cortical plate. The flap was sutured open with several retraction sutures to aid visibility as well as to avoid unnecessary exposure of the cortex, which would compromise the circulation (Fig 13-1g). A partial-thickness flap provided the opportunity to visualize the buccal without compromising the blood supply. However, this can be technically challenging and affords little support in the event of an unintended fracture of the buccal plate. The chance of salvaging a comminuted buccal plate is better if the full flap is intact. The choice of a full flap versus a split flap is a result of the clinician’s assessment of the relative advantages of the technique and comfort with the chosen technique.

There are several approaches to choose from for managing narrow ridges by performing ridge-splitting procedures. The clinician in this case chose the following treatment because it afforded a greater opportunity to recover in the event of comminution of the buccal plate.

Straight bibeveled chisels, inserted in 0.25- to 0.5-mm increments, were moved sideways no more than half their width to split the crestal part of the alveolus (Figs 13-1h to 13-1j). At a depth of 7 to 8 mm, the wide basal bone was reached, satisfying yet another prerequisite for the procedure. The anterior sextant was split to a width of 2.0 mm before inserting the pilot drill, which engaged the basal bone without any resistance between the palatal and buccal plates (Figs 13-1k and 13-1l). Their positions were confirmed with paralleling pins (Fig 13-1m). The osteotomies were completed using Latch Reamers followed by Hand Reamers to better perceive the bone’s limitations and to expand the bone further by the action of the reamers themselves (Figs 13-1n and 13-1o). Bone harvested from the flutes of the reamers was later used for grafting material over the shoulders of the implants. Six 4.0 × 8.0–mm IntegraCP Implants with 2.5-mm wells were placed (Fig 13-1p). Fig 13-1 Treatment 1: Maxillary ridge splitting with a full-thickness flap. (a) Facial view without the ill-fitting complete denture. (b) Preoperative panoramic radiograph. Note the marked sinus hypertrophy, particularly on the left side, and the adequate height of the alveolar crest in the anterior sextant. (c) Panoramic radiograph after healing of the left lateral sinus lift graft. (d and e) CBCT scan of the maxillary anterior sextant. Note the knife-edge configuration of the crest with the presence of a wide base and cancellous bone between the distinct labial and palatal cortical plates.

Guide pins confirmed the position of the seated implants in the alveolus (Fig 13-1q). The black Healing Plugs were trimmed and placed into the implant wells (Fig 13-1r). With the implants in place, the marked expansion of the ridge is evident in the immediate postoperative view of the crest (Figs 13-1s and 13-1t). One can better appreciate the extent of the expansion by comparing the clinical image at the time of uncovering with the preoperative condition (Fig 13-1u). A panoramic radiograph reveals the array of integrated implants prior to their uncovering (Fig 13-1v). The implants were uncovered with a crestal incision, and a full-arch implant-level transfer impression provided for the fabrication of a soft tissue model (Figs 13-1w to 13-1bb).

The IAC restorations were arrayed on the model and then placed (Fig 13-1cc). The postplacement radiograph demonstrates an excellent result (Fig 13-1dd). Clinical images and radiographs after 5 years (Figs 13-1ee to 13-1hh) and a clinical image after 8 years (Fig 13-1ii) reveal that not only did the implants maintain the original levels of crestal bone, but the crestal cortices seem to be denser and thicker, reflecting the bone’s normal positive response to the stress of increased functional demands. Fig 13-1 (cont) (f) A palatal guide was fabricated based on the patient’s existing denture and is checked intraorally. (g) Elevated and retracted full-thickness flap exposing only the crestal-most aspect of the alveolus to preserve the periosteal blood supply to the buccal cortical plate. (h) A bibeveled chisel is used to initiate the ridge splitting of the alveolar crest. (i) The ridge split was achieved incrementally with 0.25- to 0.5-mm depths as the chisel was moved sideways in steps no greater than half its width. (j) Chisel is contacting the wide basal bone at a depth of 7 to 8 mm. (k) Image of the two plates separated by at least 2 mm. (l) Pilot osteotomy: The 2.0-mm pilot drill is introduced between the plates to engage the basal bone. (m) Paralleling pins indicate the position of the pilot osteotomies. (n) A 2.5-mm Latch Reamer widening the pilot osteotomy at a trajectory parallel to the adjacent paralleling pin. (o) A 3.0-mm Hand Reamer with bone in its flute was used to widen the osteotomy. (p) A 4.0 × 8.0–mm implant with a 2.5-mm well was inserted with a black Healing Plug attached. (q) Multiple guide pins were inserted into the implant wells to evaluate the positioning and trajectory of the implants, which can be readily adjusted at this stage. —> Fig 13-1 (cont) (r) A trimmed black Healing Plug held by a periodontal probe is inserted into the well of an implant. (s) Sutured surgical site with obvious expansion of the ridge. (t) Postoperative panoramic radiograph. Note the use of the Sinus Lift Abutment for the right-most posterior implant. (u) Postoperative view after 5 months. Compare with Fig 13-1b to appreciate the extent of the expansion. (v) Postoperative panoramic radiograph after 5 months. (w) A 2.5-mm blue impression post seated in the well of an implant. (x) Exposed black Healing Plug prior to being removed from its implant. (y) A black Healing Plug adjacent to two 2.5-mm blue impression posts is removed. (z) Right side view of two 3.0-mm green and three 2.5-mm blue impression posts seated in their implants. (aa) Left side occlusal view of five Healing Plugs prior to their being removed. (bb) Occlusal view of 12 metal impression posts prior to the placement of their corresponding acrylic sleeves for the making of a full-arch implant-level transfer impression. —_ Fig 13-1 (cont) (cc) (cc) Clinical view after the insertion of 12 IACs. (dd) Panoramic radiograph after the insertion of 12 IAC restorations. (ee) Five-year postoperative clinical view. (ff to hh) Five-year follow-up periapical radiographs. (ii) Clinical view after 8 years of the restoration in function.

Ridge Splitting with the Two-Stage Window Technique

Unlike the direct vertical splitting of the maxilla, mandibular ridge splitting is technically more challenging and has a greater risk of unfavorable or incomplete splitting or splintering of the buccal cortex owing to the bone’s inherent features.[2,3] The two-stage window technique provides the clinician more control over the fracture location and dimensions. Posterior mandibular bone is routinely denser, less flexible, and more difficult to manipulate and expand than bone in other mandibular or maxillary sites. The following example demonstrates the two-stage bony window technique.

Treatment 2

A 57-year-old woman presented with bilaterally missing mandibular premolars and first molars with bilateral atrophy of the alveolar processes, evidenced by the loss of buccolingual dimension; however, there was adequate height of the alveolus above the mental foramen and the mandibular canal and adequate basal bone width within 8 mm of the crest on the right side to accommodate the three intended implants.

The proposed treatment was a ridge expansion via twostage mandibular ridge splitting with concomitant implant placements. Preoperative planning included panoramic and CBCT imaging, which revealed a thinning alveolar crest that still had adequate height to accommodate the intended short implants, the presence of a cancellous layer between two well-defined and distinct cortical plates, and a sufficient width of bone beginning at a depth of 8 mm (Figs 13-2a to 13-2e). The mandibular right posterior sextant site as seen in the presurgical clinical view had minimal alveolus and bulging basal bone (Fig 13-2f).

A full-thickness mucoperiosteal flap exposed the buccal plate well below the level of the wide basal bone (Fig 13-2g). A piezoelectric surgical instrument with an assortment of tips made the first cut through the cortical plate, following a course along the crest of the alveolus. The bone incision began 2 to 3 mm distal to the premolar and extended 5 to 6 mm distal to the most distal side of the intended implant. The inferior cut made at the upper limit of the wide basal bone followed the same guidelines as the crestal cut. Two vertical cuts connected the first two cuts at their mesial and distal ends (Figs 13-2h to 13-2k). A bur with a diamond file tip thinned the inferior edge of the buccal bone flap and confirmed that all of the cuts were completely through the cortical bone, particularly at the four corners (Fig 13-2l). The presence of bleeding in the corticotomy indicated that the cuts were complete; however, confirmation was still necessary. Fig 13-2 Treatment 2: Mandibular ridge splitting with a two-stage window. (a) Preoperative panoramic radiograph. (b to d) CBCT imaging of the mandibular right premolars and first molar. (e) CBCT imaging revealing buccal plate defect. Note the presence of the cancellous layer between two well-defined cortical plates, as well as sufficient width of bone at the depth of 8.0 mm. —_>

The window in the buccal plate was not mobilized (Fig 13-2m). After irrigating the surgical site, resorbable sutures closed the flap (Fig 13-2n). A CBCT scan of the mandible visibly shows the extent and location of the corticotomy cuts through the cortex (Fig 13-2o).

After a 3-week healing period, during the second surgery, a conservative crestal incision opened the lingually based flap, which was inclined toward the lingual of the crestal midline to create as wide a zone of attached gingiva as possible. Once again, in the interest of maintaining the blood supply, the buccal plate was not exposed (Fig 13-2p).

Using a Curved Chisel and an angled curette, the buccal plate was gently fractured from its cancellous layer and mobilized while remaining attached to the overlying buccal soft tissue (Fig 13-2q). A trough at least 2.0 mm wide was created for the pilot drill to initiate the splitting to the level of the basal bone to provide 2 to 4 mm of stability for the placement of the implants within the split crest (Figs 13-2r and 13-2s).

After the desired depth was established, the osteotomy was widened to 4.5 mm with a succession of incrementally wider Hand Reamers mounted on the threaded instrument adapter to provide the appropriately sized osteotomy (Figs 13-2t and 13-2u). After confirmation of the integrity of the walls and floor of the osteotomies, the implants were placed (Figs 13-2v and 13-2w). After carefully removing their black Healing Plugs, an offset handle with a 3.0-mm tip was used to gently seat the implants to their full depth (Fig 13-2x).

The implants were seated slightly deeper (by 1 to 3 mm) than the recommended 2- to 3-mm position below the crest because the edges of split bone tend to behave like an extraction socket by losing nearly 2 mm of their height during healing (Fig 13-2y). The degree of facial displacement of the buccal plate is evident to appreciate how much space was gained using this ridge-splitting procedure. A less desirable alternative would be to reduce the narrow crestal ridges if there were sufficient height of bone to permit the placement of implants.

The black Healing Plugs were trimmed and placed in the implant wells using a periodontal probe (Figs 13-2z and 132aa). The autogenous bone shavings collected during the osteotomy preparations covered the implant shoulders without Fig 13-2 (cont) (f) Preoperative clinical view after administration of local anesthetic. (g) Full-thickness mucoperiosteal flap with retraction suture was raised well below the wide basal bone. (h) A piezoelectric surgical handpiece is used to make a midline crestal cut through the cortical plate 2 to 3 mm distal to the premolar and 5 to 6 mm distal to the most distal intended implant. (i) A horizontal cut is made at the upper limit of the wide basal bone. (j) Completed horizontal cut. (k) The mesial aspect of the horizontal cut is extended vertically. (l) A diamond file tip is used to thin the inferior edge of the buccal bone flap and to confirm that all of the cuts are completely through the cortex, particularly at all four corners. (m) View of the buccal plate with the corticotomy cuts. The presence of bleeding in the cuts is a good indicator that the cuts are complete, but it is not a guarantee, so the cuts should be thoroughly inspected to ensure their completion. Note that no attempt is made to mobilize the cut buccal plate. (n) The surgical site was thoroughly irrigated and closed with resorbable sutures. (o) A CBCT scan of the mandible shows the extent and location of the corticotomy cuts. Note how the cuts are completely through the cortex. . Fig 13-2 (cont) (p) After 3 weeks, during the second phase of the ridge splitting, a lingually based crestal flap was prepared to place the implants. Note that the buccal plate was not exposed to preserve the periosteal attachment, which will be the sole blood supply for the buccal bone. (q) A Cottle Curved Chisel is used to mobilize the buccal bone. (r) A 2.0-mm-wide trough is created. (s) The 2.0-mm pilot drill is introduced directly into the wide basal bone to a depth that is sufficient for the placement of the intended implant 2 to 4 mm below the crest. (t) A 2.5-mm Hand Reamer mounted on a latch extender is being used to widen the pilot osteotomy with the same trajectory as the two adjacent paralleling pins. (u) Harvested bone within the flute of the 4.5-mm Hand Reamer attached to a latch extender. (v) After the integrity of the osteotomy walls was confirmed with a curette and any bone chips were removed, a 4.5 × 6.0–mm implant with its Healing Plug attached was inserted into its osteotomy. (w) Three implants with their black Healing Plugs attached are seated in their osteotomies. (x) An offset handle with a 3.0-mm seating tip is gently tapped to definitively seat the implant to its full depth. (y) Implants seated in the split ridge. Note that the implants are seated 2 to 4 mm deeper than the recommended 2- to 3-mm position below the crest; this is because the edges of the split behave like an extraction socket, losing 2 mm of height during healing. (z) A trimmed Healing Plug on a periodontal probe is seated into the well of its implant. (aa) Three implants with trimmed black Healing Plugs. (bb) The autogenous harvested bone shavings are gently placed over the implant shoulder since any packing of the bone may displace the implant’s position. —>

packing additional bone or grafting material between the implant bodies, since it is unnecessary for healing and doing so would have risked displacing the implants (Fig 13-2bb).

A resorbable collagen plug enhanced the closure by helping to preserve and contain the harvested bone and blood clot within the split until the surgical site healed by secondary intention (Fig 13-2cc). Although the flap closure was secure, no attempt was made to achieve primary closure because doing so would have caused undue tension on the tissues and invited possible incision breakdown and delayed healing (Fig 13-2dd). A postoperative CBCT scan confirmed the proper positioning of the implants and completion of this ridge-splitting procedure with significant displacement of the buccal plate (Figs 13-2ee to 13-2hh). Fig 13-2 (cont) (cc) (cc) A resorbable collagen plug is inserted to facilitate the maintenance of the grafted bone and blood clot as healing occurs by secondary intention. (dd) The surgical site is sutured without primary closure because primary closure would have caused undue tension on the tissues, potential incision breakdown, and delayed healing. (ee to hh) Postinsertion CBCT confirms the proper positioning of the implants and completion of the split. (ii) Periapical radiograph prior to the uncovering 4 months after implant placement. (jj) After midcrestal incision, a Lucas curette is used to remove bone over the three black Healing Plugs. Note the bone fill inside the split. (kk) The black Healing Plug is removed with a large endodontic file. (ll) Occlusal view of three implants in the widened ridge. (mm) Three guide pins were placed into the implant wells to confirm their integration and trajectories, prior to the use of a Sulcus Former. (nn) Periapical radiograph of the restored implants.

The implants’ uncovering and restoration was uneventful (Fig 13-2ii). A midcrestal incision exposed the implants with their black Healing Plugs, and a curette cleaned the bone from around the plugs (Fig 13-2jj). The plugs were removed with the help of a large endodontic reamer (Figs

13-2kk and 13-2ll). Guide pins accessed the firmness of the integration and were also used with Sulcus Formers, which rotated on their shaft to shape a bony seat for the base of the intended abutment (Fig 13-2mm). A radiograph taken after placement of the abutments shows the three implants with provisional restorations in place (Fig 13-2nn). Fig 13-3 (a) A 3D illustration of the maxillary alveolus. (b) Illustration of a split-thickness flap being prepared with a no. 15c blade at a 45-degree angle without removing the periosteum from the cortical bone. (c) A supraperiosteal preparation with a no. 15c blade elevating the loosened buccal mucosa. (d) Mucosa and submucosa are dissected in an upward direction from the underlying and intact periosteum. (e) Dissection continuing in a posterior direction.

Ridge Splitting with a Split-Thickness Flap

A split-thickness flap, also known as a partial-thickness flap , is a flap that includes the epidermis and its immediate underlying connective tissue but does not include the periosteum[4–7] (Fig 13-3). The single-step procedure has the advantage of a well-vascularized alveolar crest, which allows for ridge splitting or bone widening to be carried out with significantly less bone loss than an approach of multiple stages.[8,9] Whether to use the split-flap, full-flap, or two-stage technique is the clinician’s decision and is always based on the relative advantages of each technique in balance with individualized clinical circumstances, as well as with the clinician’s comfort level with each approach. Note that when preparing a split-thickness flap, it is easier to separate the mucosa and the underlying connective tissue from the periosteum using specially angulated or beveled scalpels.

The success of ridge splitting depends on the bone density of the ridge. According to Lekholm and Zarb,[10] there are four distinguishable classes of bone based on their density. Less dense bone can be widened with bonecondensing instruments. Soft cancellous bone can be laterally condensed between cortical drill holes, employing suitable bone condensers driven into the ridge using a soft tapping motion to advance to a depth consistent with the length of the intended implant. Dense bone has to be split prior to moving its buccal cortical lamella.

Treatment 3

The treatment of a 49-year-old patient demonstrates the maxillary ridge-splitting technique using a split-thickness flap. The preoperative radiograph and clinical image show a failing fixed prosthesis in the sites of missing maxillary central incisors and right lateral incisor as well as an atrophic maxillary anterior ridge (Figs 13-4a and 13-4b). Using a no. 15c scalpel blade, the split-thickness flap was reflected buccally and only minimally to the palatal (Figs 13-4c and 13-4d). Retraction sutures were used to keep the wound open (Fig 13-4e). A bone saw was used to make a vertical cut to a depth sufficient for the spindle of the saw to touch the alveolar bone[11] (Figs 13-4f to 13-4h). If the alveolar crest were too thin, it would have been necessary to reduce its height by cutting the periosteum and reducing the bone horizontally, with the intention of beginning the procedure further apically at a wider point in the ridge. Exercising this option, and its limits, would depend upon the ridge’s shape, height, and width at its apical dimension.

In this example, the buccal cortical bone was very thick; therefore, to avoid fracturing the ridge, it was necessary to use a very thin piercing instrument in a vertically downward and lineal direction to make several perforations through the periosteum and into the buccal cortical bone (Figs 13-4i to 13-4k). Once the buccal plate was somewhat weakened by the perforations, the saw cut was deepened using a double-beveled knife to a depth consistent with either the desired depth of the osteotomy or to the end of the beveled blade, whichever came first (Figs 13-4l and 13-4m). Then, very thin chisels were used to widen and deepen the gap while simultaneously beginning to exert a gentle pressure to displace the facial aspect of the cortical bone to the buccal. Further widening of the gap was achieved by using one or two chisels, depending on the length of the cut (Figs 13-4n and 13-4o). Fig 13-4 Treatment 3: Maxillary ridge splitting with a split-thickness flap. (a) Preoperative radiograph showing missing maxillary central incisors and right lateral incisor. (b) Clinical image reveals extensive buccal bone defect after traumatic loss of these teeth and buccal cortical bone. (c) Illustration of a transverse maxillary frontal bone section with a midcrestal cut of the mucosa marked in red . (d) Illustration of a split-thickness flap separating the mucosa from the periosteum on the palatal and labial sides with a red line marking a midcrestal cut through the periosteum. (e) Clinical image of a reflected split-thickness flap with retraction sutures attached to the adjacent mucosa. (f) Illustration of a horizontal cut ( red line perpendicular to the blue line ), which is necessary when the alveolar crest is too thin to initiate splitting the palatal and labial cortices with the bone saw. (g and h) Illustrated and clinical images of a bone saw splitting the labial and palatal cortices. (i and j) Illustrated and clinical images of a piercing instrument perforating the periosteum and labial cortical bone. (k) Clinical image of vertical cortical perforations mesial to the right canine and left lateral incisor. —_>

In this particular instance, in which the buccal plate was deemed to be especially thick, the use of the lineal vertical piercing perforations helped to avoid fractures and facilitated a successful ridge-splitting procedure. The result provided a sufficiently wide alveolar ridge for the preparation of the implant osteotomies (Fig 13-4p). Initially, a 2.0-mm pilot drill was used, and further widening was achieved with condensing instruments until the desired width was reached (Figs 13-4q and 13-4r). To facilitate the alignment of implant placements, the tip of the condensing instrument was left in the implant osteotomy adjacent to whichever implant was being placed (Fig 13-4s). A guide pin was placed into the well of each implant to confirm and, if necessary, adjust its position prior to placing the trimmed black polyethylene Healing Plugs into the wells of the implants (Figs 13-4t to 13-4v). Fig 13-4 (cont) (l and m) Illustration and clinical image of a bilaterally cutting double-beveled bladed Beaver knife (Beaver-Visitec) deepening the saw cut into the spongy bone. (n and o) Illustration and clinical image of a chisel widening and deepening the bony gap by moving the buccal bone. (p) Clinical image of a split ridge. (q) Illustration of a Meisinger condensing instrument widening the socket. (r) Clinical image of Bone Expander being inserted and, if necessary, tapped into the osteotomy of the left central incisor. (s) A 3.5 × 8.0–mm Bicon implant is placed into the site of the left central incisor while the expander instrument is maintaining the opening of the split ridge. (t) Clinical image of two guide pins seated in the well of their implants while a 3.5 × 8.0–mm Bicon implant is being placed parallel with the guide pins, into the site of the right central incisor with an inserting tip attached to a straight handle. (u) Clinical image of three seated guide pins being used to facilitate confirmation of the trajectory of the implants. If necessary, they could be moved to adjust an implant’s trajectory. (v) Clinical image of three seated implants with their trimmed Healing Plugs inserted into their wells. (w) Illustration of an implant with SynthoGraft, a pure-phase beta-tricalcium phosphate material, covering an implant and its Healing Plugs. (x) A no. 15c scalpel is used to free the mucosa by preparing in the submucosal-supraperiosteal layer of the cranial vestibulum region to ensure a tension-free closure of the mucosa. ——— >

Because no autogenous bone was harvested during the preparation of the osteotomies, the implants were only covered with blood. Alternatively, SynthoGraft, a pure-phase beta-tricalcium phosphate material, could have been mixed with the patient’s blood to cover the implants (Fig 13-4w). To ensure a tension-free mucosal closure, a submucosal-supraperiosteal relieving incision was made (Fig 13-4x). The relieving incision was made within the split flap at its apical extent. It involved making a horizontal incision through the submucosal layer over the periosteum. The incision was made far enough into the vestibule so that the blood supply to the rest of the periosteum was not compromised as the clinician advanced the flap coronally with less tension, while facilitating primary closure at the crest. Small perforations of the mucosa, which may have occurred during the preparation of the split-thickness flap, would be only a minor issue if sutured immediately with five or six sutures, because underlying the perforation is a well-vascularized periosteum. Fig 13-4 (cont) (y) (y) Postplacement radiographic image. (z) Six-month clinical image after the ridge widening and placement of the three implants and just prior to their being uncovered. (aa) Clinical image of the uncovering. (bb) Bone is removed with a round ceramic bur. (cc) View of three completely uncovered implants. (dd) View of three red 2.0-mm titanium impression posts with their corresponding acrylic sleeves prior to making an implant-level transfer impression. (ee) Clinical image of widened ridge with healed peri-implant mucosa. (ff) View of three milled and grit-blasted abutments after their being oriented and initially seated in the wells of their implants with a seating jig prior to the cementation of the TRINIA fixed partial denture. (gg and hh) Clinical and radiographic images of definitive TRINIA prosthesis after being in function for 2 years.

The postoperative radiograph reveals three well-positioned Bicon implants (Fig 13-4y). The 6-month postoperative clinical image taken prior to the uncovering of the implants shows excellent healing (Fig 13-4z). At the uncovering, any newly formed bone over the implants was easily removed with a spoon excavator or a bur (Figs 13-4aa to 13-4cc). Figure 13-4dd shows the 2.0-mm Titanium Impression Posts with their corresponding acrylic sleeves and the sutured flap. Ten days later, the Healing Abutments were removed, revealing a healed peri-implant mucosa (Fig 13-4ee).

The parallel, milled, and grit-blasted abutments are shown after being placed into the 2.0-mm implant wells (Fig 13-4ff). The implants will support a cemented threeunit TRINIA partial denture. The 2-year postplacement clinical and radiographic images reveal a satisfactory result, albeit with some scarring of the surrounding mucosa that existed before the split procedure and implant placement (Figs 13-4gg and 13-4hh). Fig 13-5 (a) Reformatted axial slice of a CBCT image of a very thin alveolar crest at the site of the maxillary right lateral incisor, subsequent to the loss of an implant. (b) Four-year recall image after widening of the alveolar crest and placement of a 3.0 × 8.0–mm Bicon implant. Fig 13-6 Treatment 4: Mandibular ridge splitting technique with a split-thickness flap: (a) Alveolar ridge being split and widened by the tapping and sideways movement of a chisel. (b) Pilot osteotomy being prepared with a 2.0-mm pilot drill. (c) Widening of the pilot osteotomy with a Meisinger widening instrument. Alternatively and preferably, the osteotomy could have been widened with 2.5-mm and successively wider Latch and Hand Reamers. (d) Clinical image of the prepared 3.0-mm osteotomy. (e) A 3.0 × 8.0–mm implant is placed with an inserting tip attached to a straight handle. (f) Clinical image of a second osteotomy and the initially seated implant. —

In situations with a very thin alveolar crest, it is advisable— although not necessary—to perform both a preoperative and postoperative CBCT or CT image (Fig 13-5).

Treatment 4

Treatment of another 49-year-old patient demonstrates the same ridge-splitting procedure in the anterior mandible, where the cortical bone is much denser and often thinner. After performing the split-thickness flap on the buccal, and minimally on the lingual, a bone saw was used to initiate a cut, and once again the double-beveled knife was used to deepen the initial saw cut.

Chisels were used to widen the crestal cut sufficiently to allow for the insertion of a 2.0-mm pilot drill (Figs 13-6a and 13-6b). Because the cortical bone was type I or II according to Lekholm and Zarb’s classification,[10] bone-widening instruments were used. The widening instruments were used to enlarge the site until it could accommodate the 3.0-mm diameter of the chosen implants (Figs 13-6c to 13-6f). Guide pins inserted into the wells of the implants not only confirmed their trajectories but also would have facilitated their repositioning, if it were necessary, prior to closure (Fig 13-6g). A tension-free wound closure was achieved using two resorbable horizontal mattress sutures to tighten the lingual periosteal tissue to the labial mucoperiosteal tissues before closing with single-knot mucosa sutures (Fig 13-6h). Fig 13-6 (cont) (g) Clinical image of two red 2.0-mm guide pins seated in the wells of their implants being used to confirm the trajectory of the implants. Although Bicon implants should ideally be placed 2 to 3 mm below the crest to achieve an optimal result, with ridge-splitting procedures, they should be placed up to 5 mm below the crest to allow for the bone resorption that will occur during healing. (h) Clinical view after two resorbable mattress sutures were used to pull the lingual periosteum up to the labial mucoperiosteum to ensure a tension-free mucosal closure. (i) Two-week postplacement clinical image of the healing site. (j) Two red 2.0-mm Titanium Impression Posts with acrylic sleeves seated in the well of the uncovered implants for the making of an implant-level transfer impression, 3 months after implant placement. (k) The prepared three-unit partial denture seated on a stone model. (l) Radiograph of TRINIA fixed partial denture after its insertion. (m and n) Clinical image of TRINIA fixed prosthesis after being in function for 19 months and 3 years, respectively.

As evidenced in a 2-week postplacement image, the tension-free sutures facilitated excellent healing (Fig 13-6i). Three months after placement of the implants, they were uncovered, and a full-arch implant-level transfer impression was made for the fabrication of a three-unit prosthesis (Figs 136j and 13-6k). During the second restorative visit, the prosthesis was easily placed without requiring any adjustments, as evidenced by the radiograph (Fig 13-6l). The 19-month and 3-year postplacement clinical images reveal an excellent hard and soft tissue result (Figs 13-6m and 13-6n).

Screw-Retained Cortical Graft Technique

As previously discussed, ridge deficiencies in the anterior maxilla often present aesthetic concerns, even after successful ridge-splitting and implant placement procedures.

Typically, mucogingival surgeries mask both these vertical and horizontal defects with soft tissue and connective tissue grafts. Although these procedures are often effective and frequently performed at the time of implant placement, they are not ideal.

Alternatively, another effective treatment uses a cortical grafting procedure in which a harvested block of bone from the mandibular ramus is cut into two thin cortical plates. Once the plates are cut, one cortical plate is attached to the facial and one to the palatal of the ridge with osteosynthesis screws. Bone chips from the graft residue and synthetic grafting material are placed into the space formed between the two grafted plates. This technique is shown in the following description of a successful treatment of a 27-year-old woman who sustained the traumatic loss of her maxillary left canine. Fig 13-7 Treatment 5: Maxillary screw-retained cortical grafts (Khoury or 3D technique). (a) A reflected full-thickness mucoperiosteal flap over the maxillary left canine reveals a thin crestal ridge with a deep saddle and broad buccal plate defects. saddle and broad buccal plate defects. (b to d) Clinical images of a block graft being harvested from the posterior mandible at the angle of the ramus prior to being sectioned into two thin plates. (e) Clinical image of the sectioned plates being grafted to the palatal and buccal sides of the alveolar bone with osteosynthesis screws. (f) The newly formed space between the palatal and buccal grafted plates is filled with autogenous bone chips and synthetic grafting material. (g) CBCT scan shows the bone-grafted site 4 months before the removal of the osteosynthesis screws and just prior to the placement of the implant. (h) A periapical radiograph immediately after the placement of the IAC. (i) A 7-year postoperative radiograph revealing an increase in mineralization of the crestal bone.

Treatment 5

A full-thickness flap was performed, exposing the maxillary left canine site. In addition to a pronounced vertical defect in the ridge crest, there was a broad depression in the buccal plate (Fig 13-7a). Using a bone saw, a block graft was harvested from the posterior mandible at the angle of the ramus and sectioned into two thin plates with osteosynthesis screws (Figs 13-7b to 13-7e). One cortical graft plate was fastened to the buccal and the other to the palatal of the ridge. With the cortical grafts securely attached to the ridge, the newly formed buccal, palatal, and crestal space was filled with bone chips from the harvesting and mixed with synthetic grafting material (Fig 13-7f). A CBCT scan shows the bone-grafted site 4 months before the removal of the osteosynthesis screws, just prior to placement of the implant (Fig 13-7g). A comparison of the periapical radiograph taken on the day of the IAC placement with the radiograph taken 7 years after the IAC placement reveals an increase of bone mineralization throughout the years of the IAC in function (Figs 13-7h and 13-7i).

Conclusion

There are a number of treatments to augment both the width and height of a deficient alveolar ridge. This chapter demonstrated three different techniques for ridge splitting: the split flap, full flap, and multiple stages (two-stage). Additionally, a screw-retained cortical grafting procedure was shown, which addresses the aesthetic challenges associated with narrow ridges. Regardless of the technique, there are prerequisites that must be satisfied before executing a ridge split. First, the alveolus must be able to accommodate an implant at a safe distance from the inferior alveolar nerve, mental foramen, and the sinus floor. Second, the height of the basal bone above the mandibular canal and mental foramen must allow for the secure engagement of the implant’s apex, which is 1 to 2 mm beyond the depth of the split bone. Third, the alveolus must have a core of identifiable cancellous bone to provide not only a blood supply but also a thickness to facilitate the propagation of a fracture to split the ridge to allow for its expansion.

Success with screw-retained cortical grafting techniques requires the cortical grafts to be stable, covered with soft tissue, and thin enough to facilitate their vascularization. For all of the demonstrated techniques, the short and narrow Bicon implants facilitated their execution and success.

References

1. Schropp L, Wenzel A, Kostopoulos L, Karring T. Bone healing and soft tissue contour changes following single-tooth extraction: A clinical and radiographic 12-month prospective study. Int J Periodontics Restorative Dent 2003;23:313–323.

2. Enislidis G, Wittwer G, Ewers R. Preliminary report on a staged ridge splitting technique for implant placement in the mandible: A technical note. Int J Oral Maxillofac Implants 2006;21:445–449.

3. Cano J, Campo J, Ewers R. Expansion of the alveolar bone crest in two stages: Two clinical cases. Oral Surg 2011;4:30–34.

4. Scipioni A, Bruschi GB, Calesini G. The edentulous ridge expansion technique: A five-year study. Int J Periodontics Restorative Dent 1994;14:451– 459.

5. Rahpeyma A, Khajehahmadi S, Hosseini VR. Lateral ridge split and immediate implant placement in moderately resorbed alveolar ridges: How much is the added width? Dent Res J (Isfahan) 2013;10:602–608.

6. Agrawal D, Gupta AS, Newaskar V, Gupta A, Garg S, Jain D. Narrow ridge management with ridge splitting with piezotome for implant placement: Report of 2 cases. J Indian Prosthodont Soc 2014;14:305–309.

7. Khairnar MS, Khairnar D, Bakshi K. Modified ridge splitting and bone expansion osteotomy for placement of dental implant in esthetic zone. Contemp Clin Dent 2014;5:110–114.

8. Mounir M, Beheiri G, El-Beialy W. Assessment of marginal bone loss using full thickness versus partial thickness flaps for alveolar ridge splitting and immediate implant placement in the anterior maxilla. Int J Oral Maxillofac Surg 2014;43:1373–1380.

9. Seemann R, Perisanidis C, Traxler H, Ewers R. Split-thickness flap with a semicircular punched-ridge pedicled periosteal flap for implant restoration in highly atrophic patients: A technical note. Int J Oral Maxillofac Implants 2014;29:e10–e12.

10. Lekholm U, Zarb GA. Patient selection and preparation. In: Brånemark PI, Zarb GA, Albrektsson T (eds). Tissue-Integrated Prostheses. Chicago: Quintessence, 1985:199–209.

11. Khoury F, Khoury C. Mandibular bone block grafts: Diagnosis, instrumentation harvesting techniques and surgical procedures. In: Khoury F, Antoun H, Missika P (eds). Bone Augmentation in Oral Implantology. London: Quintessence, 2006:115.

14

Atrophic Maxillary Ridges

Rolf Ewers | Paolo Perpetuini | Rudolf Seemann | Tom De Wit | Imraan Sarvan | Marieke Coetzer | Kristina Pisarik

Over 150 years ago, renowned surgeon Julius Wolff observed that healthy bone adapts to any pressure applied or removed from it.[1,2] Inspired by the 1860s work of Karl Culmann regarding the principles of structural engineering, Wolff described changes in the trabecular structures of the human femur in response to loading. The resorption of bone in the human mandible, an example of bone undergoing an adaptive change in response to changing conditions, is better understood in light of Wolff’s law, which states, “in a healthy person or animal, bone will adapt to the loads under which it is placed.”

After the extraction of teeth, the jawbone, consistent with Wolff’s hypothesis, becomes less dense and weaker owing to the lack of stimuli and is resorbed toward its apical base. The process of resorption projects a medial posterior force in the maxilla and lateral anterior force in the mandible. Nearly a century after Wolff’s postulation, Atwood created a classification for atrophying jaws, which was adjusted in 1988 by Cawood and Howell to become today’s recognized method of classifying jaw atrophy.[3–6] The Cawood and Howell classification distinguishes six classes of atrophy: I, dentate alveolar ridge; II, empty alveolus; III, high wellrounded; IV, knife-edged; V, low well-rounded; and VI, low depressed[5] (Fig 14-1). A variety of procedural techniques have been developed to treat these atrophic categories. Fig 14-1 Classes of atrophy adapted from Cawood and Howell.[5]

Fig 14-2 Schematic diagram showing pseudoprognathism caused by progressive atrophy of the maxillomandibular alveolar ridge. Fig 14-3 (a) Schematic drawing of osteotomy in Le Fort I plane as described by Bell in 1975.[9] (b) The horseshoe Le Fort I osteotomy as described by Härle and Ewers in 1980,[7] leaving the palatal bone in place (vertical pedicled sandwich plasty). (Reprinted with permission from Lambrecht.[10] )

Solutions for Atrophic Maxillary Ridges

For several decades, the most popular technique for treating maxillary bone atrophy was the lateral sinus lift in conjunction with bone augmentation. The procedure involves dissecting and gently lifting the Schneiderian membrane, a fragile layer of soft tissue lining the maxillary sinuses. The space between the newly elevated membrane and the bony floor of the sinus is then filled with a mixture of synthetic bone, the patient’s blood, and any available autogenous bone. Several other bone augmentation procedures include bone block grafts, guided bone regeneration (GBR), and vascularized bone grafts, as described in chapter 19.

Horseshoe Le Fort I osteotomy

Unfortunately, there exists a group of compromised patients for whom the use of a lateral sinus lift or other augmentation procedure runs the risk of damaging the mucosa of the maxillary sinuses and nasal floor, or whose medical condition simply does not allow it. In response to the pressing needs of these patients, the horseshoe Le Fort I osteotomy was used and has helped many elderly patients switch from a complete denture to an implant-supported prosthesis, particularly when there was minimal horizontal or vertical bone.[7]

Skeletal incongruence between the maxilla and mandible would worsen the situation by causing their ill-fitting dentures to be subjected to further stress and, in turn, often induce a crossbite that would affect their facial profile, create a jutting jaw and collapsed upper lip, and age them before their time (Fig 14-2). Despite their severe class VI atrophies, this cohort of patients has been successfully treated with the horseshoe Le Fort I osteotomy[8,9] (Fig 14-3).

Although the horseshoe Le Fort I osteotomy method has proven successful, it is a risky operation that requires a second operative site for the harvesting of autogenous bone and, in most cases, a separate surgery 6 months later for the placement of the implants.[10] Additionally, the treatment usually takes over a year to complete; therefore, it was a boon when it was found that patients who have an extremely atrophic maxilla could be treated without exposure to the Fig 14-4 (a) Panoramic radiograph of a successful treatment with four zygomatic implants. (b) Subcutaneous infection around the implant at the level of the zygoma. (c) View of cutaneous infection with fistulae on the maxilla. Fig 14-5 (a) Dehiscence on the buccal of the implant body. (b) Removal of two integrated zygomatic implants with forceps.

potential morbidity and extended treatments of a horseshoe Le Fort I procedure by utilizing the short and narrow Bicon implants. A number of treatments are presented in this chapter, demonstrating the successful application of Bicon short and narrow implants in cases of severe maxillary alveolar atrophy.

Zygomatic implants

Maló et al[11] found that placing four long implants in the zygomatic arch inclined in a position to bypass the maxillary sinuses was an effective means for treating an atrophic maxilla; however, because of the length of zygomatic implants (35.0 to 55.0 mm) and the 1- to 3-mm ridge height of atrophic jaws, implants such as these require delicate placement by a highly skilled surgeon to avoid injury to the eye, the orbit, and the infraorbital nerve.

For most patients, two zygomatic implants are placed bilaterally, and for almost every patient, immediate loading is possible provided that cross-arch splinting of the implants can be provided. This procedure allows for the use of both fixed and fixed-removable prostheses; however, because zygomatic implants frequently emerge palatally, fixed-removable prostheses are more often chosen for hygienic reasons. The incidence of implant bending is another important factor to be considered, because the zygomatic implant is primarily anchored in zygomatic bone and minimally in the maxillary crest. Failure to pay attention to a perfectly balanced occlusion, articulation, rigid cross-arch stabilization, or prudent and meticulous use of cantilevers can result in disastrous consequences.

Although zygomatic implants function well for many patients, there can be challenges and failures for a variety of reasons, such as infection around the implant at the level of the zygoma, cutaneous infection with fistulae, dehiscence on the buccal of the implant body, recurring sinus infections, and breaking or loosening of the implant (Fig 14-4). All of these issues inevitably lead to the removal of one or more zygomatic implants (Fig 14-5). Nevertheless, the alternative of a lateral sinus lift for patients with very limited bone volume would be imprudent because most of a threaded implant would be anchored only by synthetic bone-graft material.

Fig 14-6 Clinical situation after the removal of two integrated zygomatic implants because of mucosal infection. These were later replaced with Bicon short implants. Fig 14-7 (a) Palatal view of abutments for the hybrid restoration on a stone model. (b) Intaglio of the finished TRINIA hybrid prosthesis. (c) Postoperative panoramic radiograph of a zygomatic implant rescue case with three short Bicon implants and a small sinus lift in a patient with minimal maxillary bone.

Because zygomatic implants are used in patients with limited bone volume, the repercussions of their failure are even more severe than the consequences of a traditional implant’s failure; furthermore, the placement of a new zygomatic implant is very challenging or even impossible for many patients. Fortunately for patients with atrophic jaws, and particularly for those with failed zygomatic implants, the use of short implants has proven to be an efficient and effective approach to restoring atrophic jaws (Fig 14-6).

Bicon short implants

A single fixed prosthesis with a substructure of TRINIA— a computer-aided design/computer-assisted manufacturing (CAD/CAM) fiber-reinforced resin material (see chapter 11)—satisfies the requirements of two distinctly different implant systems, serving as the base for an unconventional hybrid restoration. The hybrid restoration is screw retained for the longest of implants and cement-retained for the shortest of implants (Figs 14-7a and 14-7b). The TRINIA material offers enough rigidity to limit the bending moments of the longest zygomatic implants while providing space for the incorporation of screw-retained cylinders. It is also sufficiently flexible to allow for the prosthesis to be cemented on the shortest implants of the Bicon system. The unconventional treatment, which combines very long and very short implants in support of a multipurpose TRINIA prosthesis, proved successful for the patient in Fig 4-7, who presented with minimal maxillary bone (Fig 14-7c).

In a 63-year-old patient with minimal maxillary bone (Fig 14-8a), the placement of four zygomatic implants was executed with the help of three-dimensional (3D) planning (Figs 14-8b and 14-8c); however, infection and pain developed, and the two left zygomatic implants were removed (Figs 14-8d and 14-8e). In response to that failure, piezoelectric surgical instruments were used to perform a sinus lift in preparation for the placement of four 4.0 × 5.0–mm implants (Figs 14-8f and 14-8g). When the implant sites were ready, the osteotomies were prepared with a pilot drill, and the implants were placed with augmentation material (Figs 14-8h to 14-8k). The implants and Healing Plugs were covered by primary closure of a tension-free flap.

Six months later, the implants were uncovered, and Healing Abutments were placed (Figs 14-8l and 14-8m). Subsequently, implant- and abutment-level impressions were made for the fabrication of a master cast, and occlusal relationships were recorded. The patient’s Dolder bar and fixed-removable prosthetic device were replaced with a fixed TRINIA prosthesis, which was fastened to the remaining zygomatic implants with screws and cemented onto the Bicon abutments (Figs 14-8n to 14-8q). The new prosthesis was not only a functional success, but it was more pleasing to the patient because of its reduced size and weight and enhanced aesthetics (Fig 14-8r). The drastic size disparity between the zygomatic implants and the short Bicon implants is evident in the postoperative radiograph (Fig 14-8s). Fig 14-8 (a) Preoperative panoramic radiograph of a 63-year-old patient with minimal maxillary bone. (b) Image from 3D planning for the placement of four zygomatic implants. (c) Panoramic radiograph of four zygomatic implants with Dolder bar. (d) Left lateral view of Dolder bar with the two zygomatic implants with dehiscence prior to their being removed. (e) Panoramic radiograph after removal of the two left zygomatic implants. (f) A mucoperiosteal flap was elevated to expose the lateral wall of the antrum, and a piezoelectric surgical instrument was used to start osteotomy preparation. (g) Clinical view of prepared lateral window prior to its elevation. (h) The sinus mucosa is elevated next to four prepared implant osteotomies. (i) After completion of the sinus lift, paralleling pins confirm trajectories of osteotomies. (j) View of implants seated with their polyethylene Healing Plugs in the well of each implant. (k) View of trimmed Healing Plugs in the implants and augmentation material in the newly formed cavity. (l) Uncovering of four Bicon implants after 6 months of healing. —_> Fig 4-8 (cont) (m) Palatal view of the two zygomatic implants and four Healing Abutments. (n) Palatal view of the two zygomatic implants and four Bicon abutments on a stone model. (o) Palatal view of the maxillary TRINIA prosthesis on a stone model. (p) Palatal view of the four Bicon abutments and two zygomatic implant analogs. (q) Postplacement facial image of the new maxillary TRINIA prosthesis in occlusion. (r) View of the new TRINIA prosthesis (left) next to the old fixed-removable denture (right) . (s) Postoperative radiograph showing size disparity between the zygomatic and short Bicon implants restored with a TRINIA prosthesis.

Implants in the Maxillary Tuberosity

Although the preceding treatment illustrates the remarkable capacity of Bicon implants and restorative materials, the restoration of the maxilla remains a challenge caused in part by the large percentage of spongy bone and the overall poor bone quality of the maxilla.

According to Cawood and Howell,[5] most cases of class V and VI severely atrophic maxillae have a maxillary tuberosity with at least 5 to 6 mm of alveolar crestal bone. Prior to the idea of placing very long implants in the zygoma, there had been reports about placing implants in the maxillary tuberosity. More recent studies have demonstrated good long-term results with threaded implants placed in the maxillary tuberosity; for example, a systematic review of five studies showed a 95% survival rate among 289 implants in a follow-up period of 144 months after placement.[12] Although Lekholm and Zarb[13] have already illustrated the vast differences between the consistency and vascularization of the bone structures of the mandible and maxilla, Ulm et al[14] further described the fatty spongiosa with excellent vascularization in the maxillary tuberosity as well as with their histomorphometric cadaver studies, which found a volume difference of trabecular bone structure between men (27.9%) and women (20.2%) (Fig 14-9).

The treatments of the following eight patients reveal the efficacy of placing short implants in the anterior maxilla and in the tuberosity, where there is scarce but well-vascularized bone.

Fig 14-9 Schematic drawing of the classification of qualitative bone supply according to Lekholm and Zarb[13] and corresponding microradiographs. (Reprinted with permission from Lambrecht.[10] ) Fig 14-10 (a) Panoramic radiograph of a severely atrophied maxilla, class VI, in a 55-year-old patient. (b) Postoperative panoramic radiograph of four 3.0 × 8.0–mm and two 4.0 × 5.0–mm implants and one Sinus Lift Abutment. (c) Palatal view of the six definitively seated Bicon abutments. (d) Finished maxillary full-arch TRINIA prosthesis. (e) Postplacement palatal view of maxillary full-arch TRINIA prosthesis. (f) Postplacement panoramic radiograph of maxillary full-arch TRINIA prosthesis. (g and h) One-year postplacement intraoral facial view and radiograph of maxillary full-arch TRINIA prosthesis in occlusion.

Treatment 1

In the first treatment, a 4.0 × 5.0–mm Bicon implant was placed in the left maxillary tuberosity of a 55-year-old patient with extreme class VI atrophy (Fig 14-10a). A Sinus Lift Abutment was used to avoid the inadvertent displacement of the implant into the maxillary sinus (Fig 14-10b). After uneventful healing, the six implants were uncovered, and a full-arch TRINIA prosthesis was fabricated and cemented (Figs 14-10c to 14-10e). A panoramic radiograph reveals a satisfactory result (Fig 14-10f). The 1-year postplacement clinical and radiographic images show excellent ongoing results (Figs 14-10g and 14-10h). Fig 14-11 (a) Preoperative radiograph of an edentulous right posterior maxilla with very little crestal bone height in the molar region and sufficient bone height in the maxillary tuberosity for a short Bicon implant in a 56-year-old patient. (b) Postoperative radiograph with one narrow 3.0 × 8.0–mm implant in the area of the right canine, one 4.0 × 8.0–mm implant in the area of the right first premolar, and one 4.5 × 6.0–mm implant in the maxillary tuberosity. (c) Maxillary ridge after removal of the Healing Abutments and shortly before placement of the six-unit TRINIA partial denture. (d) Lateral view of the six-unit TRINIA partial denture with the abutments placed into the bores of the prosthesis with petroleum jelly. (e) Postoperative radiograph of the six-unit TRINIA partial denture. (f and g) Two-year postoperative intraoral view and radiograph of the six-unit TRINIA partial denture.

Treatment 2

In the next scenario, a 56-year-old patient presented with an edentulous right posterior maxilla. Radiographs revealed that there was very little bone present, especially in the molar area (Fig 14-11a). In lieu of performing a sinus lift and graft, the following implants were placed: a 3.0 × 8.0–mm implant in the site of the right canine, a 4.0 × 8.0– mm implant in the site of the right first premolar, and a 4.5 × 6.0–mm implant in the right tuberosity (Fig 14-11b). Six months later, the implants were uncovered, and a six-unit fixed TRINIA prosthesis was fabricated and placed (Figs 14-11c and 14-11d). Although the tuberosity implant was quite distal, the panoramic radiograph reveals that it was well tolerated (Fig 14-11e). The 2-year postplacement images also show satisfactory results (Figs 14-11f and 14-11g).

Treatment 3

In another instance, a 71-year-old patient presented with mobility of the maxillary left lateral incisor and a four-unit maxillary partial denture with failed endodontic therapy extending from the left canine to the first molar (Fig 14-12a). Ten weeks after the removal of the loose lateral incisor and failed partial denture, the following implants were placed: a 4.5 × 8.0–mm implant in the site of the left lateral incisor, a 3.0 × 8.0–mm implant in the site of the left first premolar, and a 4.5 × 6.0–mm implant in the left tuberosity (Figs 14-12b and 14-12c). After 16 weeks of healing, the implants were uncovered, and a seven-unit fixed TRINIA prosthesis was placed (Fig 14-12d). The 2-year postplacement images show satisfactory results (Figs 14-12e and 14-12f).

Treatment 4

In the fourth treatment, a 57-year-old woman presented with loose implants that had been placed 10 years previously following a sinus lift and graft (Figs 14-13a and 14-13b). The patient’s left posterior implants and remaining teeth were removed, and 10 weeks later, because there was no permanent sinus perforation, three 4.0 × 5.0–mm implants were placed in the sites of the maxillary left premolars and the maxillary tuberosity (Fig 14-13c). Six months later, they were uncovered, an implant-level transfer impression was made, and a five-unit TRINIA prosthesis was fabricated and placed (Figs 14-13d and 14-13e). The postplacement clinical and radiographic images reveal a satisfactory treatment (Figs 14-13f to 14-13h). Fig 14-12 (a) Preoperative radiograph in a 71-year-old patient. (b) Intraoral view of the maxillary ridge and seated implants with Healing Plugs. (c) Postoperative radiograph of a 4.5 × 8.0–mm implant in the site of the left lateral incisor, a 3.0 × 8.0–mm implant in the site of the left first premolar, and a 4.5 × 6.0–mm implant in the left tuberosity. (d) Lateral view of the seven-unit maxillary TRINIA partial denture on a stone model. (e and f) Two-year postplacement intraoral view and radiograph of the seven-unit TRINIA partial denture. Fig 14-13 (a) Preoperative radiograph in a 57-year-old woman. (b) Reflection of intraoral view of the periodontal situation around implant crowns of the left first and second molars. (c) Postplacement radiograph of three short 4.0 × 5.0–mm Bicon implants. The posterior implant is positioned in the maxillary tuberosity. (d) Lateral view of the five-unit TRINIA partial denture on a stone model. (e) Intaglio view of a five-unit TRINIA partial denture with abutments. (f) Intraoral view of the three parallel milled and grit-blasted abutments. (g and h) Postplacement clinical image and radiograph of the five-unit TRINIA partial denture. Fig 14-14 (a) Simple acrylic splint with four small metal balls. (b) Panoramic radiograph of simple acrylic splint with four small metal balls. (c) Osteotomy being enlarged with a red 4.0-mm Hand Reamer attached to a threaded instrument adapter on a handpiece. (d) Harvested bone in the flute of a red 4.0-mm Hand Reamer attached to a threaded instrument adapter on a handpiece. (e) A 4 × 5–mm implant being placed into the osteotomy with a 2.5-mm Implant Inserter/Retriever. (f) Seated implant within the osteotomy. (g) Cut polyethylene Healing Plug inserted into the 2.5-mm well of the implant. (h) Harvested bone placed over the shoulder of the implant. (i) Postoperative panoramic radiograph of the four short 4.0 × 5.0–mm Bicon implants. (j) Palatal view of the four parallel milled and grit-blasted abutments on a maxillary stone model. —>

Treatment 5

In another treatment, a 66-year-old patient presented with a class VI atrophic maxilla; however, there was sufficient bone height and width in the right and left canine area for placement of two 4.0 × 5.0–mm implants. Another two 4.0 × 5.0–mm implants were placed, one in each maxillary tuberosity. A simple acrylic splint with four attached metal balls was used as a positioning aid (Figs 14-14a and 14-14b). The preparation of the implant bed and placement of a 4.0 × 5.0–mm implant is shown in Figs 14-14c to 14-14i. After 6 months of healing, the implants were uncovered, and a full-arch TRINIA prosthesis was finalized before placement (Figs 14-14j and 14-14k). The TRINIA base extended beyond the first molars without complication (Fig 14-14l). The patient’s smile and facial profile were improved by the maxillary prosthesis, as evidenced by the intraoral clinical and radiographic images and the 2-year recall panoramic radiograph (Figs 14-14m to 14-14r).

Treatment 6

The sixth treatment concerned a 74-year-old patient who presented with a subperiosteal implant appliance that had become loose and infected after 10 years of use (Fig 1415a). After the removal of the periosteal appliance, a number of implants were placed, of which only one survived in the anterior maxilla (Fig 14-15b). Two were removed at different times during treatment, and one was left in but not functional. During the preparation of the alveolar crest for additional implants, a massive area of bone resorption was uncovered in the area from the right central incisor to the left first premolar (Fig 14-15c). The bone cavity was debrided and determined to not have enough bone to effectively place an additional implant. Alternatively, two 4.0 × 5.0–mm Bicon implants were placed, one in each maxillary tuberosity (Figs 14-15d to 14-15i). After an appropriate period of healing, a full-arch TRINIA prosthesis was fabricated and placed, producing a stable and satisfactory result made possible through the use of the restorative material TRINIA as well as the two short Bicon implants and the old anterior implants (Fig 14-15j). Fig 14-15 (a) Panoramic radiograph with maxillary subperiosteal implant appliance. (b) Panoramic radiograph after removal of subperiosteal implant appliance, with three implants remaining. (c) Mucoperiosteal flap elevated to expose the alveolar crest with massive bone resorption from the right central incisor to the left first premolar. (d) Osteotomy being enlarged with a blue 3.0-mm Hand Reamer attached to a threaded instrument adapter. (e) A 4.0-mm-wide osteotomy is prepared in the maxillary tuberosity. (f) Cut polyethylene Healing Plug placed into the 2.5-mm well of the seated implant. (g) Harvested bone collected on the surgical instrument. (h) Harvested bone being placed over the shoulder of the implant. (i) Postplacement panoramic radiograph of two 4.0 × 5.0–mm implants in the maxillary tuberosities. (j) Six-month recall panoramic radiograph of two 4.0 × 5.0–mm implants in the maxillary tuberosities with a TRINIA prosthesis.

Treatment 7

The seventh patient was a healthy 63-year-old man with a class VI atrophic maxilla into which four 4.0 × 5.0–mm implants were placed (Figs 14-16a and 14-16b). After 6 months of healing, the implants were uncovered and restored with a full-arch TRINIA prosthesis (Figs 14-16c to 14-16e). The postplacement clinical and radiographic images reveal healthy mucosa and stable bone (Figs 14-16f to 14-16h). Fig 14-16 (a) Panoramic radiograph of a 63-year-old man with extreme maxillary atrophy, class VI. (b) Postplacement panoramic radiograph of four short 4.0 × 5.0–mm Bicon implants in the interantral region of the maxilla. (c) Lateral view of the four parallel milled and grit-blasted abutments on a maxillary stone model. (d) Occlusal view of the TRINIA prosthesis on a stone model. (e) Posterior palatal view of the TRINIA prosthesis on a stone model. (f) View of four definitively seated abutments in a class VI atrophic maxilla. (g) Postplacement panoramic radiograph of the TRINIA prosthesis. (h) Patient’s smile with the TRINIA prosthesis.

This patient was a participant in the prospective study at the University Hospital for Cranio-Maxillofacial and Oral Surgery in Vienna, Austria, for treating severely atrophic edentulous mandibles and maxillae with TRINIA prostheses supported by only four short Bicon implants.[15] In almost 6 years, 20 patients were treated with 80 short Bicon implants in the maxilla. Of the 80 implants, 64 were 4.0 × 5.0 mm, 14 were 3.0 × 8.0 mm, and 2 were 3.5 × 8.0 mm. Only three patients lost implants, which were immediately replaced (for one patient, the failed implant was replaced with two implants). During the first year, the survival rate was 98.6%, and since the second year, the survival rate has been 93.5%. The prosthetic success has been 100% for all 20 patients because the three patients with failed implants were able to function with only three implants while their replacement implants were osseointegrating.

Treatment 8

Although most of the treatments mentioned previously were treatments for elderly patients, maxillary atrophy can be present in younger patients as well. Just as was possible for the patients described above, restorations can be made for younger patients despite severe atrophy. An example is the treatment of an 18-year-old girl who was diagnosed with acute lymphoblastic leukemia as a child, shortly before her second birthday. After undergoing an aggressive treatment of chemotherapy, she relapsed less than 2 years later. She eventually overcame her illness, but the repeated chemotherapy and 18 Gy of radiation treatment resulted in stunted skeletal development and complete anodontia. At 18 years old, she presented with painful, failing, and poorly developed primary teeth (Fig 14-17a). Most of her teeth had no roots or very short, atrophic roots with numerous periodontal abscesses, which needed to be removed (Fig 14-17b).

In addition to extreme atrophy, the patient also had a small mouth with limited opening—31 mm wide and less than 8 mm of vertical space—between her maxillary ridge and mandibular teeth. Because of the extremely limited vertical dimension of her occlusion and reduced vascularity of her irradiated bone, bone grafts and conventional threaded implants were not possible options; therefore, 4.0 × 6.0–mm and 3.0 × 8.0–mm Bicon implants provided the solution. All of the restorative materials required customization or pediatric sizes to fit the exceptionally tight space. A provisional denture was fabricated as a transitional prosthesis and to evaluate her tolerance of a 2.0-mm increase in the vertical dimension of occlusion. Fig 14-17 (a) Preoperative panoramic radiograph of 18-year-old patient’s failing maxillary teeth and atrophic roots. (b) Panoramic radiograph of edentulous maxilla. (c) Postplacement panoramic radiograph of four 4.0 × 6.0–mm and two 3.0 × 8.0–mm Bicon implants. (d) Digital volume tomography image of the patient’s skull. Note how little space the maxilla offers even for short implants. (e) Purple retentive telescopic coping being modified on a Universal Abutment to provide space for a restoration.

A ridge split was performed, and two 3.0 × 8.0–mm and four 4.0 × 6.0–mm Bicon implants were placed in the maxilla (Figs 14-17c and 14-17d). The implant placement was aided by the use of Hand Reamers, which expanded the delicate bone. After 9 months, the implants were uncovered, an implant-level impression was made, and the black Healing Plugs were left in place to act as Healing Abutments. At a following visit, an acrylic wax-up mounted on a TRINIA substructure with Universal Abutments was used to confirm the midline, occlusion, lip support, vertical dimension, and general aesthetics. The abutments were seated with the guidance of a light-cured resin jig.

Purple retentive and silver nonretentive copings were modified before being placed onto the seated abutments prior to the seating of the waxed teeth arrangement (Figs 14-17e and 14-17f). After a satisfactory wax try-in, the waxed teeth arrangement was returned to the laboratory for final processing along with the Universal Abutments, and the Healing Abutments were reseated into their implants.

Following the final processing, the retentiveness and path of insertion of the definitive prosthesis was evaluated in the laboratory by means of a verification jig. On the day of placement, the six abutments were seated through the aid of a seating jig, after which the fit of the abutments, copings, and prosthesis was confirmed. The copings, which were modified to be rings to provide vertical clearance, were then cemented within the TRINIA telescopic prosthesis, and the patient’s occlusion was reaffirmed (Figs 14-17g to 14-17i). Fig 14-17 (cont) (f) Facial view of six modified telescopic copings seated on Universal Abutments on a stone model. (g) Maxillary TRINIA full-arch prosthesis prior to cementation of the retentive copings. (h) Intaglio view of TRINIA prosthesis with cemented copings, which were modified to provide prosthetic clearance. (i) Postoperative panoramic radiograph of six seated Universal Abutments and modified copings.

Conclusion

Because patients with severely atrophic maxillary and mandibular arches have extremely limited bone volume, there are few options as reliable or feasible as the placement of short and narrow implants. Not only are Bicon implants capable of fitting in tight spaces, but they also often promote bone gain in situations where other implants experience bone loss.

In addition to greatly reducing the need for bone grafting, short and narrow implants facilitate treatment by eliminating the need for highly skilled surgeons. Most dentists who are well trained and have experience with the Bicon system can place implants in seemingly impossible situations. Furthermore, unlike other implants, short and narrow Bicon implants can be easily restored. Although the Bicon implant has many clinical attributes, its biggest asset in treating atrophic arches is its small size.

References

1. Frost HM. Wolff’s Law and bone’s structural adaptations to mechanical usage: An overview for clinicians. Angle Orthod 1994;64:175–188.

2. Wolff J. Das Gesetz Der Transformation Der Knochen. Berlin: Verlag von August Hirschwald, 1892.

3. Atwood DA. Postextraction changes in the adult mandible as illustrated by microradiographs of midsagittal sections and serial cephalometric roentgenograms. J Prosthet Dent 1963;13:810–824.

4. Atwood DA, Coy WA. Clinical, cephalometric, and densitometric study of reduction of residual ridges. J Prosthet Dent 1971;26:280–295.

5. Cawood JI, Howell RA. A classification of the edentulous jaws. Int J Oral Maxillofac Surg 1988;17:232–236.

6. Ulm C, Solar P, Blahout R, Matejka M, Gruber H. Reduction of the compact and cancellous bone substances of the edentulous mandible caused by resorption. Oral Surg Oral Med Oral Pathol 1992;74:131–136.

7. Härle F, Ewers R. Horseshoe-shaped osteotomy with bone interposition in order to raise the maxillary crest. An operating method stopped after the experiment [in German]. Dtsch Zahnarztl Z 1980;35:105–107.

8. Yerit KC, Posch M, Guserl U, et al. Rehabilitation of the severely atrophied maxilla by horseshoe Le Fort I osteotomy (HLFO). Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2004;97:683–692.

9. Bell W. Le Fort I osteotomy for correction of maxillary deformities. J Oral Surg 1975;33: 412–426.

10. Lambrecht JT. Oral and Implant Surgery: Principles and Procedures. London: Quintessence, 2009:344–350.

11. Maló P, Nobre M de A, Lopes I. A new approach to rehabilitate the severely atrophic maxilla using extramaxillary anchored implants in immediate function: A pilot study. J Prosthet Dent 2008;100:354–366.

12. Lopes LFDP, da Silva VF, Santiago JF, Panzarini SR, Pellizzer EP. Placement of dental implants in the maxillary tuberosity: A systematic review. Int J Oral Maxillofac Surg 2015;44:229–238.

13. Lekholm U, Zarb GA. Patient selection and preparation. In: Brånemark PI, Zarb GA, Albrektsson T (eds). Tissue-Integrated Prostheses. Chicago: Quintessence, 1985.

14. Ulm C, Kneissel M, Schedle A, et al. Characteristic features of trabecular bone in edentulous maxillae. Clin Oral Impl Res 1999;10:459–467.

15. Seemann R, Marincola M, Seay D, Perisanidis C, Barger N, Ewers R. Preliminary results of fixed, fiber-reinforced resin bridges on four 4- × 5-mm ultrashort implants in compromised bony sites: A pilot study. J Oral Maxillofac Surg 2015;73:630–640.

15

Atrophic Mandibular Ridges

Rolf Ewers | Paolo Perpetuini | Rudolf Seemann | Kristina Pisarik

In preprosthetic surgery, the term augmentation refers to the measures taken to restore lost bone and soft tissue; however, this chapter discusses the use of existing bone. Ideally, augmentation of alveolar bone should constitute full regeneration of the tissue (ie, restitutio ad integrum), not simply spatially repaired tissue with scar formation; therefore, the goal of osseous and soft tissue reconstructive surgery should be the restoration of both the form and function of the original tissue.[1,2]

Bone Augmentation Procedures

Bone is a highly dynamic system that retains its structure through a balance of various influences; this is known as modeling and remodeling , and it is a contin­ uous process.[3,4] Osteoclasts resorb old bone, while osteoblasts form a new bone matrix.[5] A preponderance of resorbing activity may result in the atrophy of areas of the jaw, which may need to be built up again, or augmented, before receiv­ ing an implant. Although by definition, augmentation procedures simply add to resorbed or damaged tissues and do not fully restore them, they are essential in providing enough bony tissue for the treatment of atrophic tissues.

The microcirculation of the tissue plays a major role through metabolic micro­ regulation during the processes of remodeling; recruitment; and activation of os­ teoclasts, osteoblasts, and their precursor cells.[6,7] Reconstructive bone grafting of osseous defects does not always result in well­vascularized bone, even when the defect is filled.[8] True regeneration is not just a mixture of devitalized inclusions or scar tissue; it implies that the defect is filled with viable mineralized tissue that models and remodels as bone. Fig 15-1 (a) Original classification of bone augmentation techniques. Class I: microanastomosed free bone flaps, class II: distraction osteogenesis, class III: pedicled segmental osteotomies with an inlay graft, class IVa: onlay grafts, class IVb: nonvascularized allografts. The quality of bone is dependent on the vascularization of the graft or the induction of vascularization in native bone, which is symbolized in the illustration by its place on the pedestal. New classification of bone augmentation techniques: (b) Class I: Microanastomosed free bone flap. (c) Class II: Distraction osteogenesis. (d) Class III: Pedicled segmental osteotomy. (e) Class IV: Bone morphogenetic induction graft. (f) Class Va: Onlay block graft. (g) Class Vb: Guided bone regeneration. (Reprinted with permission from Ewers.[10] ) Methods used for the regeneration of bone defects can be differentiated according to the vitality of the bone graft, the extent of consolidation, and the marginal integration. These conditions can only be verified by long­term clinical findings; however, since routine biopsy analyses are imprac­ tical, hard tissue augmentation can be empirically classified based upon the vascularization of the grafting procedure.[9] We propose that the earlier classification outlined by Ewers,[10] with five classifications for bone regeneration techniques in defect reconstruction, be divided into six classes according to vascularization, or induction of vascularization: class I, microanastomosed free bone flaps; class II, distraction os­ teogenesis; class III, pedicled segmental osteotomies with nonvascularized interpositional grafts, inlay grafts; class IV, bone morphogenetic induction grafts, tent pole situations; class Va, nonvascularized bone grafts, onlay grafts; and class Vb, guided bone regeneration[2,11] (Fig 15­1). Fig 15-2 (a) Vertical distraction osteogenesis enhancing alveolar height. (b) Multidirectional distraction osteogenesis (bone transport). (c) Vertical pedicled sandwich plasty enhancing alveolar height. (Reprinted with permission from Ewers.[10] )

Fig 15-4 Comparison of distraction methods: (a) Vertical distraction with distraction appliance. The black circle shows mucosal perforation, which is the point of least resistance and is prone to infection. (b) Vertical PSP with microplate application. (c) Stabilization of the mobilized bone segment with the aid of the implant. (Reprinted with permission from Ewers.[10] )

Distraction osteogenesis produces a much more vi­ tal, well­vascularized isotropic bone than is found in bone grafts, and it also takes on the same conformation as the distraction callus, but the primary use of alveolar distraction is for the enhancement of alveolar height or width[12–14] (Fig 15­2). The theory that distracted bone is always vascular­ ized was confirmed in histologic studies (Fig 15­3); howev­ er, there are disadvantages to this method of bone regen­ eration. Aside from the patient’s discomfort in wearing a distracting device for several months, there is also the risk of the distracting device perforating the mucosa, as well as the potential dislocation of the bony segment. Additionally, the use of short Bicon implants negates the need for dis­ traction techniques altogether, for if there is sufficient bone (8 or 9 mm) to accommodate a distraction device, there is more than enough bone to receive a short Bicon implant.

Pedicled sandwich plasty

The vertical and transversal one­ or two­step pedicled sand­ wich plasty (PSP) is the preferred grafting method where

Fig 15-3 The undecalcified histologic preparation of the core specimen, taken before placing the implant, reveals excellent vascularized new bone formation between the boundaries of the former osteotomy (yellow lines ), which distracts the bone to a width of about 10 mm. (Reprinted with permission from Ewers.[10] ) there is minimal bone, except where there is also minimal soft tissue, such as from trauma or burns. The PSP method of grafting works well because of the excellent blood supply in the maxilla and mandible. A pedicled bone segment can be immediately moved up to a distance of 9 or 10 mm and stabilized with osteosynthesis plates and screws, and the gap in between is filled with a graft material (Fig 15­4).[15–21] In some respects, any procedure in which autogenous bone or augmentation materials are used with at least a two­layer coverage of vascularized bone may be considered an inlay graft and bone class III, whereas an augmentation with at least three walls is considered a special form of an inlay plasty. In addition to the PSP, there are other surgical proce­ dures considered to be bone class III as well, such as ridge preservation through filling a tooth socket, inlay augmenta­ tions, and sinus lift procedures. When regenerating minimal bone over the alveolar nerve, the PSP is the surgical proce­ dure of choice, since it has the least amount of morbidity.

A demonstration of this method is presented with the treatment of a 48­year­old patient. The preoperative ra­ diograph revealed an insufficient amount of vertical bone above the mandibular canal for implants in tooth sites from the mandibular left second premolar to the left second mo­ lar (Fig 15­5a). An incision and osteotomy were made in the same manner as for gradual vertical distraction osteo­ genesis.[22] The mucoperiosteal flap was detached only on the buccal side and minimally elevated from the alveolar ridge because bone vascularization can only be assured when the mobilized bone segment is minimally detached from the periosteum (Fig 15­5b). This minimal detachment of the periosteum will provide either class II bone similar to vertical distraction or class III bone similar to a vertical sand­ wich plasty. If the periosteum were completely detached, it could result in nonvascularized bone comparable to class Va bone of an onlay graft. Fig 15-5 (a) Preoperative radiograph showing minimal vertical bone above the mandibular canal. (b) Partial dissection of the mental nerve without causing disturbances of sensation. (c) A box-shaped osteotomy in a vertical PSP is prepared with a piezoelectric surgical instrument. Note the narrow space between the instrument and the mental nerve. (d) The bone segment is supported by two small cortical bone segments harvested from the lateral mandible, which act as pillars to prevent a relapse or closing of the achieved gap. (e) The occlusal bone segment was moved by approximately 5 mm, with a lingual periosteal soft tissue pedicle flap with two microosteosynthesis plates and screws. (f) Augmentation material fills the void. —>

The osteotomies can be performed with either a Khoury saw or piezoelectric surgical instruments, as first described by Vercellotti[23] (Fig 15­5c). It is prudent to stabilize the split bone by placing two small pieces of cortical bone harvested from the mandible to act as pillars to prevent the cortical bone from collapsing (Fig 15­5d). Immediately following this stabilization, the elevated bone was also secured with micro or mini osteosynthesis plates and screws (Fig 15­5e). A re­ sorbable membrane was then placed on the lingual side. The resulting cavity was filled with augmentation material, which was then covered with a second resorbable membrane (Fig

15­5f). A periosteal tissue flap was performed on the buccal side and closed in two layers[24] (Fig 15­5g). Radiopacity was minimal because all of the resorbing augmentation material was composed of porous materials (ie, hydroxyapatite or tri­ calcium phosphate) (Fig 15­5h).

After 3 months, the titanium screws and plates were re­ moved, and two 4.0 × 5.0–mm Bicon implants were placed (Fig 15­5i). To avoid extensive loss of the periosteum over the buccal bone, only the plates and screws close to the implants were removed, and the remaining titanium mate­ rial was left in situ. The increasing calcification caused by the remodeling of graft material into newly formed bone was evident after just 3 months. Osseointegration of the two short implants was also revealed in a radiograph tak­ en 4.5 years after placement. The remnant osteosynthesis materials had been removed in the meantime (Fig 15­5j). The former cavity was completely filled with newly mineral­ ized bone, and the peri­implant mucosa proved healthy in an image of the Integrated Abutment Crowns (IACs) after placement (Fig 15­5k).

The use of Bicon short implants has revolutionized the way in which implants can be placed.[25,26] They not only provide the opportunity to avoid grafting procedures, but more importantly, they provide options for many pa­ tients who may not otherwise be able to have an implant­ supported prosthesis. For example, short and narrow im­ plants have been successfully placed for patients with man­ dibular atrophies such as very thin bone between 6 and 7 mm in the interforaminal region; a thin alveolar crest throughout the mandible; edentulous space of only 4.0 mm between teeth; and a minimal amount of alveolar crest above the inferior alveolar nerve, which is the most com­ mon location of nerve injuries. Fig 15-5 (cont) (g) Resorbable sutures stabilize the pedicled periosteal tissue flap to achieve a double-layer closure. (h) Postoperative radiograph taken immediately after the PSP. Note the minimal radiopacity of the augmentation material. (i) Postoperative radiograph taken after partial removal of the mini plates and screws and placement of two 4.0 × 5.0–mm Bicon implants. (j) Postoperative radiograph taken after 4.5 years of loading of the implants, during which time the osteosynthesis materials had been removed completely, the IACs placed, and the mandibular left third molar extracted. (k) Postoperative clinical image of IACs at 4.5-year recall.

In addition to its short height of 5.0 mm and its narrow width of 4.0 mm, the Bicon implant’s other features—a 1.5­degree bacterially sealed locking­taper connection (ie, implant abutment interface [IAI]) and a sloping shoulder— also contribute to the prevention of problems such as peri­ mucositis or peri­implantitis in susceptible patients who have compromised bone or soft tissues, including those with irradiated bone, bisphosphonate or denosumab treatments, bone marrow transplants, and diabetes.

Atrophic bone with full-arch TRINIA restoration

In 2010, a preliminary study was conducted to determine the survival rates of short implants in atrophic bone.[27] In this study, the survival of fixed partial dentures supported by four 4.0 × 5.0–mm implants with 2.5­mm wells was assessed for 10 patients with highly atrophic mandibles. There were no incidences of breaking or chipping of the TRINIA partial dentures, and of the 40 implants, only 1 was lost before loading. The patient whose implant failed to osseointegrate was a 56­year­old woman with a Cawood and Howell[28] class VI atrophic mandible and a fracture of the right horizontal ramus (Fig 15­6a).

The fracture was stabilized with osteosynthetic material over the course of 4 years, after which time the stabilizing material was removed (Figs 15­6b and 15­6c). The pan­ oramic and cephalometric radiographs taken shortly before the implant placements revealed severe mandibular atro­ phy, with a bone height of about 7 mm in the inter foraminal chin region, and almost no alveolar ridge (Figs 15­6d and 15­6e).

An epiperiostal split­thickness flap was prepared to raise the periosteum only where the implants would be placed, and then the osteotomies were prepared for the placement of the four 4.0 × 5.0–mm Bicon implants (Figs 15­6f to 15­6m). The implants were covered with the bone collected from the Latch Reamers, and the wound was closed with nonresorbing su­ tures (Figs 15­6n and 15­6o). Fig 15-6 (a) Panoramic radiograph of a 56-year-old woman’s class VI atrophic mandible with a fracture of the right horizontal ramus. (b) Panoramic radiograph after treating the mandibular fracture with stabilizing osteosynthetic materials. (c) Panoramic radiograph 4 years later, after removing the osteosynthetic materials. (d) Panoramic radiograph 1 year after removing the osteosynthetic materials and before placing the implants. (e) Lateral cephalometric radiograph taken before placing the implants. The patient’s anterior mandibular height is about 7 mm or less. Note the sharp remnant of the nonresorbed posterior mental spine. (f) Clinical view of highly atrophic alveolar ridge caused by class VI atrophy. (g) The mental muscle bellies are identified after the incision and epimuscular dissection. (h) The crestal part of the mental muscle is removed. (i) An osteotomy is enlarged with a 3.0-mm Latch Reamer. (j) A 4.0 × 5.0–mm Bicon implant with a black Healing Plug is placed into the osteotomy. (k) A seating tip is used to insert the implant into the osteotomy. (l) Definitively seated 4.0 × 5.0–mm implant. —> Fig 15-6 (cont) (m) View of mandibular ridge and four seated implants with trimmed black Healing Plugs. (n) Harvested bone is placed over the shoulder of the implants. (o) Sutured site with nonresorbable sutures. (p) Postoperative panoramic radiograph with four 4.0 × 5.0–mm Bicon implants. Note the minimal bone even for short implants. (q) Four blue, 2.5-mm guide pins indicate the trajectory of the implants after the uncovering. (r) Four impression posts with acrylic sleeves for the making of an implant-level transfer impression. (s) Four white PEEK Healing Abutments seated in the implants. —

In addition to showing the position of the four implants, the postoperative radiograph revealed that the mandible was only slightly larger than the short implants (Fig 15­6p). After 3 months of healing, the implants were uncovered, a full­arch implant­level transfer impression was made, and polyetheretherketone (PEEK) Healing Abutments were placed into the wells of the implants (Figs 15­6q to 15­6s). The panoramic radiograph showed a satisfactory result (Fig 15­6t). An interarch occlusal relationship was recorded during the second prosthetic visit, and the fit and aesthetics of the prosthesis were confirmed during the third visit.

Subsequently, a computer­aided design/computer­ assisted manufacturing TRINIA base was fabricated with wax and composite teeth (Figs 15­6u to 15­6z). The use of a light­cured resin seating jig facilitated the positioning of the four abutments into the implant wells, and the application of petroleum jelly prevented the abutments from falling out of the seating jig (Fig 15­6aa). Alternatively, the abutment positioning could have been achieved with the TRINIA pros­ thesis itself (Fig 15­6bb). The waxed try­in was adjusted, and another bite registration was recorded (Fig 15­6cc).

The definitive TRINIA prosthesis was fabricated and sub­ sequently placed; however, movement of the left anterior implant was detected, and the implant was removed. Thus, the prosthesis was cemented on only three abutments (Figs 15­6dd to 15­6gg). The postoperative clinical image of the patient’s smile, as well as the panoramic and cephalomet­ ric radiographs, revealed successful positioning of the full­ arch prosthesis on only three abutments even after 4 years (Figs 15­6hh to 15­6ll). Fig 15-6 (cont) (t) Panoramic radiograph with the PEEK Healing Abutments in situ. (u) Wax rim try-in and bite registration is recorded 10 days after the uncovering of the implants to record the midline, smile line, incisal length, and trajectory of teeth. (v) Mandibular wax teeth arrangement mounted on a TRINIA base. Note the bores of the TRINIA base in the reflection. (w) Four parallel milled abutments on a stone model. (x) Light-cured resin seating jig over abutments on a stone model. (y) Mandibular wax teeth arrangement mounted on a TRINIA base with four seated abutments. (z) Mandibular wax teeth arrangement mounted on a TRINIA base on four abutments inserted into implant analogs on a stone model. (aa) Two posterior abutments are seated by means of the seating jig with petroleum jelly in its bores. (bb) TRINIA base and wax teeth arrangement is used to facilitate the seating of the abutments. (cc) Occlusion with wax teeth arrangement is confirmed prior to making occlusal registration with a recording material. (dd) Occlusal view of the mandibular full-arch TRINIA prosthesis. (ee) Anterior view of four parallel milled abutments on a soft tissue model. (ff) Mandibular full-arch TRINIA prosthesis seated over abutments on a soft tissue model. (gg) Mandibular full-arch TRINIA prosthesis. Fig 15-6 (cont) (hh) Patient’s smile after placement of the TRINIA prosthesis. (ii) Panoramic radiograph after the loss of the left anterior implant. (jj) Lateral cephalometric radiograph. Note the long bilateral cantilevers. (kk) Four-year postplacement intraoral view of the TRINIA prosthesis. (ll) Three-year postplacement panoramic radiograph shows no sign of bone loss or complications despite the loss of the left anterior implant. Fig 15-7 (a) Preoperative radiograph of mandible with little bone above the mandibular canal on both sides. (b) Detail of radiograph marking 7.0 mm bone over the mandibular canal.

A postoperative review of the radiographs revealed that the implant that failed to osseointegrate had been placed in the exact location where an osteosynthesis screw had been placed. Fortunately, despite the fact that she was the only patient with a failed implant, she was able to function very well with her TRINIA prosthesis on only three implants. The prosthetic success rate for the treatment of severely atrophic mandibles with four 4.0 × 5.0–mm Bicon implants with TRINIA prostheses after almost 6 years is 100%.

Atrophic Mandibles Without Augmentation

Because nerve damage is the most common complication of implant placement in the mandible, treatments in which implants are placed in atrophic mandibles without augmen­ tation procedures are of particular interest. This section demonstrates the treatment of three patients.

Treatment 1

A 61­year­old patient presented with bilaterally missing man­ dibular posterior teeth and an extensive vertical atrophy of the alveolar bone on the left side with only about 7 mm of bone remaining over the inferior alveolar nerve (Figs 15­7a and 15­7b). According to Cawood and Howell’s[28] classifica­ tion, this degree of atrophy would be considered class V to VI. Without augmentation, two 3.0 × 8.0–mm implants were placed in the sites of the mandibular left first premolar and the right second premolar, and three 4.0 × 5.0–mm implants were placed in the sites of the mandibular left first molar and second premolar and the mandibular right first molar. The osteotomies were initially prepared with a 2.0­mm pilot drill rotating at 1,100 rpm with external irrigation (Figs 15­7c and 15­7d). Once the osteotomies were finalized, the implants were seated with polyethylene Healing Plugs in their 2.0­ and 2.5­mm wells to indicate the trajectory of the implants (Figs 15­7e and 15­7f). Harvested bone was then placed over the implants (Fig 15­7g). Fig 15-7 (cont) (c) Osteotomy being prepared with a 2.0-mm pilot drill rotating at 1,100 rpm with external irrigation in the site of the mandibular left first molar. (d) Finalized osteotomies in the sites of the mandibular left first premolar and first molar. (e) Seated implants within their osteotomies with polyethylene Healing Plugs indicating the trajectories of the implants. (f) Trimmed polyethylene Healing Plugs inserted into the 2.0- and 2.5-mm wells of the implants. (g) Harvested bone is placed over the implants. (h) Postoperative radiograph of left side after placement of implants and IACs. (i) Postoperative radiograph revealing bone gain on the left side. (j) Postoperative radiograph after placement of implants and IACs. Note the proximity of the inferior alveolar nerve to the implants without any sign of nerve disturbance. (k) Four-year postoperative radiograph. (l) Six-year postoperative clinical view of the left side with no signs of peri-implantitis.

Radiographs, computed tomography, or cone beam computed tomography scans should be taken after any difficult procedure.[10] The postoperative radiographs in this case revealed excellent osseointegration (Figs 15­7h and 15­7i). After 4 years of healing, the radiographs continued to show excellent osseointegration and even bone gain around the implants, both of which had already been re­ ported[29] (Figs 15­7j and 15­7k). The intraoral clinical view after 6 years also showed healthy tissue around the abut­ ments with no sign of peri­implantitis[30–39] (Fig 15­7l).

c Fig 15-8 (a) Preoperative radiograph of a mandibular canal with class V to VI atrophy and approximately 7 mm of bone between the alveolar crest and the inferior alveolar nerve at the site of the mandibular left second molar. (b) A measuring device for the osmotic tissue expander is used to estimate the size of the mucosa expansion of the alveolar ridge between the site of the mandibular left first molar and second premolar. (c) An osmotic tissue expander is inserted through a mucosal incision into a submucosal tunnel. (d) The expander is almost fully inserted into the submucosal tunnel. (e) The mucosa is visibly expanded after the widening with the tissue expander. (f) Lingual mucosa defect caused by the osmotic expander slipping out of its submucosal tunnel and perforating the mucosa. (g) The alveolar ridge shows scarring after the perforated mucosa healed.

Treatment 2

The second patient was 43 years old when he presented with a severe class V to VI atrophy (Cawood and Howell[28] ) over the left inferior alveolar nerve with approximately 7 mm of bone remaining between the alveolar crest and the inferior alveolar nerve in the area of the mandibular left second molar (Fig 15­8a). Originally, the treatment plan was to use a long threaded implant after a preparatory procedure to widen the mucosa with an osmotic tissue expander (Dental Cylinder, Osmed) (Figs 15­8b to 15­8e), followed by an augmentation procedure. The tissue expander worked at first, but after 25 days of expansion, the mucosa was perforated on the lingual side. The expander had slipped out of its submucosal tunnel,

causing the tissue to immediately collapse and create an un­ favorable soft tissue defect (Figs 15­8f and 15­8g).

According to the literature,[40] this complication is uncom­ mon; nonetheless, a decision was made to use a 3.0 × 8.0– mm implant in the mandibular left first molar site and a 4.0 × 5.0–mm implant in the mandibular left second molar site (Fig 15­8h). The postoperative panoramic radiograph re­ vealed the expected closeness of the 4.0 × 5.0–mm implant to the inferior alveolar nerve (Fig 15­8i). After 3 months of healing, an implant­level transfer impression was taken, and the IACs were placed. The radiographic results were very satisfactory (Figs 15­8j and 15­8k). The 4­year postopera­ tive radiographic and clinical images confirm the continued success of the treatment (Figs 15­8l and 15­8m). Fig 15-8 (cont) (h) Seated 3.0 × 8.0–mm and 4.0 × 5.0–mm implants within their osteotomies prior to the placement of trimmed polyethylene Healing Plugs into their 2.0- and 2.5-mm wells, respectively. (i) Postoperative radiograph of the implants. Note the proximity of the posterior implant to the left inferior alveolar nerve. (j and k) Postoperative radiographs after placement of the two IACs. Note the proximity of the posterior implant to the left inferior alveolar nerve. (l and m) Four-year postoperative clinical and radiographic images of the two IACs. b c Fig 15-9 (a and b) Facial and lateral views of a 64-year-old woman with class VI mandibular atrophy and an extremely small lower third of her face. (c) Preoperative panoramic radiograph revealing extreme mandibular atrophy. Note that the upper part of the mandible is not mandibular bone, but rather the nonresorbed posterior mental spine. (d) Lateral cephalo- ~~~~~ metric radiograph of the extreme mandibular atrophy and the nonresorbed posterior mental spine.

Treatment 3

The third patient was a 64­year­old woman with an extreme Cawood and Howell[28] class VI atrophy of the mandible, a narrow chin, and an exceptionally small lower third of her face (Figs 15­9a and 15­9b). Additionally, her posterior mental spine had not resorbed and was completely intact (Figs 15­9c and 15­9d); therefore, a plateau had formed in the anterior mental part of the mandible where the implants were to be placed (Figs 15­9e to 15­9h). The postoperative panoramic radiograph reveals the four interforaminal and anterior 4.0 × 5.0–mm implants in place (Fig 15­9i). Fig 15-9 (cont) (e) Four paralleling pins seated in the pilot osteotomies indicate the positioning and trajectory for the implants. (f and g) Two 4.0 × 5.0–mm implants with 2.5-mm wells are placed into the osteotomy, the first with a 2.5-mm seating tip attached to a Threaded Offset Handle and the second with a 2.5-mm Implant Inserter/ Retriever. (h) Four blue 2.5-mm guide pins indicate the trajectory of the implants. (i) Postoperative panoramic radiograph with four implants. (j) Uncovering after 3 months of healing. The implants were mostly covered with newly formed bone because of the bony wall on the lingual side of the nonresorbed posterior mental spine. (k) Bone is removed from over the implant with a round bur until it is completely uncovered. Note the high bony wall on the lingual side. (l) View of three white PEEK Healing Abutments and one titanium Healing Abutment 3 weeks after implant uncovering. (m) Four blue 2.5-mm titanium impression posts with corresponding blue acrylic sleeves in place for the making of a full-arch implant-level transfer impression. (n) Ten days after the impression, a wax arrangement of teeth was made to confirm the aesthetics of the prosthesis. (o) Occlusion is checked with the wax arrangement of teeth. —_

After 3 months of healing, a mucosal flap was elevated, and a round bur was used to remove the newly formed bone over the implants (Figs 15­9j and 15­9k). An implant­lev­ el transfer impression was made after another 3 weeks of mucosal healing, and an initial occlusal registration was taken (Figs 15­9l and 15­9m). Subsequently, an aesthetic and functional confirmation of a wax arrangement of teeth was made, and another occlusal registration was taken (Figs 15­9n and 15­9o). The abutments and completed TRINIA prosthesis were seated and checked on a stone model prior to being seated intraorally (Figs 15­9p to 15­9s). During the third restoration appointment, the abutments and the full­arch TRINIA prosthesis were placed, and the nec­ essary adjustments were made (Figs 15­9t to 15­9w). Clinical images present a lengthened lower third of the face because of the increased anterior vertical height and an excellent smile line despite her severe mandibular atrophy (Figs 15­9x to 15­9z). The 2­year panoramic radiograph revealed the an­ terior placement of the implants and the bilateral cantilever aspect of the TRINIA prosthesis (Fig 15­9aa).

Conclusion

Despite a slightly higher implant failure rate in patients with tumors, it is evident that short implants are an effec­ tive solution for atrophic mandibles, not only because they eliminate the need for intensive augmentation procedures, but also because they provide the opportunity for bone growth around the implant. Considering the thin bone of atrophic jaws, bone gain is a unique clinical benefit of Bicon short implants in addition to their small size, which allows for placement in extremely limited spaces. Although the sandwich plasty technique can be used to restore a pos­ terior edentulous mandibular free­end, short implants can be readily placed without bone regeneration techniques and, more importantly, without the physical and financial costs to the patient and dentist.[41] Overall, short implants facilitate a simpler surgery with successful, lasting results for patients with atrophic mandibles and limited options.

References

1. Jensen OT. Dentoalveolar modification by osteoperiosteal flaps. In: Fonseca RJ, Turvery TA, Marciani RD (eds). Oral and Maxillofacial Surgery, vol 1, ed 2. Philadelphia: Saunders, 2008:471–478.

2. Ewers R, Tomasetti B, Ghali GE, Jensen OT. A new biologic classification of bone augmentation. In: Jensten OT (ed). The Osteoperiosteal Flap. Chicago: Quintessence, 2010:19–42.

3. Rauch F, Travers R, Glorieux FH. Intracortical remodeling during human bone development: A histomorphometric study. Bone 2007;40:274–280.

4. Schopper C, Moser D. Biomaterials and bone repair. In: Ewers R, Lambrecht JT, eds. Oral Implants Bioactivating Concepts. Chicago: Quintessence, 2012:35–40.

5. Probst A, Spiegel HU. Cellular mechanisms of bone repair. J Invest Surg 1997;10:77–86.

6. Leunig M, Yuan F, Berk DA, Gerweck LE, Jain RK. Angiogenesis and growth of isografted bone: Quantitative in vivo assay in nude mice. Lab Invest 1994;71:300–307.

7. Hansen-Algenstaedt N, Joscheck C, Wolfram L, et al. Sequential changes in vessel formation and micro-vascular function during bone repair. Acta Orthop 2006;77:429–439.

8. Aghaloo TL, Moy PK. Which hard tissue augmentation techniques are the most successful in furnishing bony support for implant placement? Int J Oral Maxillofac Implants 2007;22 suppl:49–70.

9. Ewers R, Goriwoda W, Schopper C, Moser D, Spassova E. Histologic findings at augmented bone areas supplied with two different bone substitute materials combined with sinus floor lifting. Report of one case. Clin Oral Implants Res 2004;15:96–100.

10. Ewers R. Implant surgery. In: Lambrecht JT, ed. Oral and Implant Surgery: Principles and Procedures. London: Quintessence, 2009:420–773.

11. Ewers R. Bone regeneration techniques and bone classification. In: Ewers R, Lambrecht JT (eds). Oral Implants: Bioactivating Concepts. Chicago: Quintessence, 2013.

12. Michieli S, Miotti B. Lengthening of mandibular body by gradual surgicalorthodontic distraction. J Oral Surg 1977;35:187–192.

13. Block M. Biologic basis of alveolar distraction osteogenesis. In: Jensen OT (ed). Alveolar Distraction Osteogenesis. Chicago: Quintessence, 2002:17–28.

14. Kojimoto H, Yasui N, Goto T, Matsuda S, Shimomura Y. Bone lengthening in rabbits by callus distraction. The role of periosteum and endosteum. J Bone Joint Surg Br 1988;70:543–549.

15. Schettler D. Sandwich technique with cartilage transplant for raising the alveolar process in the lower jaw [in German]. Fortschr Kiefer Gesichtschir 1976;20:61–63.

16. Schettler D, Holtermann W. Clinical and experimental results of a sandwichtechnique for mandibular alveolar ridge augmentation. J Maxillofac Surg 1977;5:199–202.

17. Ewers R, Schicho K, Truppe M, et al. Computer-aided navigation in dental implantology: 7 years of clinical experience. J Oral Maxillofac Surg 2004; 62:329–334.

18. Ewers R, Fock N, Millesi-Schobel G, Enislidis G. Pedicled sandwich plasty: A variation on alveolar distraction for vertical augmentation of the atrophic mandible. Br J Oral Maxillofac Surg 2004;42:445–447.

19. Enislidis G, Ewers R. Vertical augmentation of atrophic mandibles— Pedicled sandwich-plasty or distraction osteogenesis? Br J Oral Maxillofac Surg 2005;43:439.

20. Jensen OT, Kuhlke L, Bedard JF, White D. Alveolar segmental sandwich osteotomy for anterior maxillary vertical augmentation prior to implant placement. J Oral Maxillofac Surg 2006;64:290–296.

21. Jensen OT. Alveolar segmental “sandwich” osteotomies for posterior edentulous mandibular sites for dental implants. J Oral Maxillofac Surg 2006;64:471–475.

22. Millesi-Schobel GA, Millesi W, Glaser C, Watzinger F, Klug C, Ewers R. The L-shaped osteotomy for vertical callus distraction in the molar region of the mandible: A technical note. J Craniomaxillofac Surg 2000;28:176–180.

23. Vercellotti T. Essentials in Piezosurgery: Clinical Advantages in Dentistry. Chicago: Quintessence, 2009.

24. Sclar A. Soft Tissue and Esthetic Considerations in Implant Therapy. Chicago: Quintessence, 2003.

25. Neldam CA, Pinholt EM. State of the art of short dental implants: A systematic review of the literature. Clin Implant Dent Relat Res 2012;14:622–632.

26. Karthikeyan I, Desai SR, Singh R. Short implants: A systematic review. J Indian Soc Periodontol 2012;16:302–312.

27. Seemann R, Marincola M, Seay D, Perisanidis C, Barger N, Ewers R. Preliminary results of fixed, fiber-reinforced resin bridges on four 4- × 5-mm ultrashort implants in compromised bony sites: A pilot study. J Oral Maxillofac Surg 2015;73:630–640.

28. Cawood JI, Howell RA. A classification of the edentulous jaws. Int J Oral Maxillofac Surg 1988;17:232–236.

29. Urdaneta RA, Daher S, Leary J, Emanuel K, Chuang SK. Factors associated with crestal bone gain on single-tooth locking-taper implants: The effect of nonsteroidal anti-inflammatory drugs. Int J Oral Maxillofac Implants 2011;26:1063–1078.

30. Urdaneta RA, Daher S, Leary J, Emanuel KM, Chuang SK. The survival of ultrashort locking-taper implants. Int J Oral Maxillofac Implants 2012; 27:644–654.

31. Müller L, Kistler F, Bayer G. Predictable success with mini implants: Minimal invasive implantation simple and practicable. J Zahnmed 2011;2:62–67.

32. Birdi H, Schulte J, Kovacs A, Weed M, Chuang SK. Crown-to-implant ratios of short-length implants. J Oral Implantol 2010;36:425–433.

33. Chou HY, Müftü S, Bozkaya D. Combined effects of implant insertion depth and alveolar bone quality on periimplant bone strain induced by a widediameter, short implant and a narrow-diameter, long implant. J Prosthet Dent 2010;104:293–300.

34. Urdaneta RA, Rodriguez S, McNeil DC, Weed M, Chuang SK. The effect of increased crown-to-implant ratio on single-tooth locking-taper implants. Int J Oral Maxillofac Implants 2010;25:729–743.

35. Bonfante EA, Suzuki M, Carvalho RM, et al. Digitally produced fiber-reinforced composite substructures for three-unit implant-supported fixed dental prostheses. Int J Oral Maxillofac Implants 2015;30:321–329.

36. Urdaneta RA, Leary J, Panetta KM, Chuang SK. The effect of opposing structures, natural teeth vs. implants on crestal bone levels surrounding single-tooth implants. Clin Oral Implants Res 2014;25:e179–e188.

37. Urdaneta RA, Marincola M. The Integrated Abutment Crown, a screwless and cementless restoration for single-tooth implants: A report on a new technique. J Prosthodont 2007;16:311–318.

38. Urdaneta RA, Marincola M, Weed M, Chuang SK. A screwless and cementless technique for the restoration of single-tooth implants: A retrospective cohort study. J Prosthodont 2008;17:562–571.

39. Urdaneta RA, Leary J, Lubelski W, Emanuel KM, Chuang SK. The effect of implant size 5 × 8 mm on crestal bone levels around single-tooth implants. J Periodontol 2012;83:1235–1244.

40. Mertens C, Thiele O, Engel M, Seeberger R, Hoffmann J, Freier K. The use of self-inflating soft tissue expanders prior to bone augmentation of atrophied alveolar ridges. Clin Implant Dent Relat Res 2015;17:44–51.

41. Ewers R. Bone standard clinical situations. In: Ewers R, Lambrecht JT (eds). Oral Implants: Bioactivating Concepts. Chicago: Quintessence, 2012:225–383.

16

Factors Affecting Bone Levels and Restorations of Short Implants

Rainier A. Urdaneta | Sung-Kiang Chuang | Joseph Leary | Vincent J. Morgan

At the outset, it is reasonable to acknowledge the concerns of those in the dental community who are taken aback when they see towering crowns sitting atop implants one-fifth of their length. Commonly, the clinician’s initial response is that the increased occlusal stresses will result in bone loss, because the concept is counterintuitive and contradicts the accepted notion of a normal crown-to-root ratio (CRR), which is a fundamental lesson in every dentist’s prosthetic development. Hesitation around unconventional ideas in science is a familiar motif, from Galileo to the Wright brothers, and today it has led to confusion and apprehension in exploring the limits of tolerable forces regarding crown-to-implant ratios (CIRs) and the use of short implants.

In part, the confusion stems from a misunderstanding of the concept of CRR, which is an idea that relates to teeth, not implants. The normal CRR for a tooth is 1:2, the supporting root structure being twice the length of the crown it supports. This is the basic level of tolerance; however, there is considerably more support possible in the dental apparatus. There is a range within which force can be increased until the tooth is fractured or exfoliated. The variables in this equation are the bone and the periodontal ligament. Within the acceptable range, the periodontal ligament absorbs and distributes increasing occlusal forces, and the bone adapts: It responds to the increased stress by growing denser and thicker. Figure 16-1 shows an instance in which excessive occlusal forces associated with bruxing traumatized the crowns of the patient’s teeth for over 20 years, and yet the bone adapted by becoming thicker and denser.

In addition to resistance to the notion of a reverse CIR, there is a tendency to equate increased occlusal force with potential bone loss. This is because clinicians are conflating the idea of trauma from occlusion, an idea usually associated with bone loss resulting from increased occlusal forces in the presence of periodontal disease, with the effects of increased forces in the absence of a diseased condition. Increasing occlusal stress on teeth in the presence of periodontal disease will result in bone loss; however, increasing occlusal stress on teeth (eg, in bruxism) in a mouth free of disease will result in the bone undergoing a positive adaptation by growing denser and thicker, or by eventually resulting in fracture or mobility of the tooth. In the treatment of the bruxing patient, a TRINIA prosthesis was fabricated to replace the damaged dentition (see Figs 16-1c and 16-1d). Fig 16-1 (a) Facial view of a patient whose bruxism traumatized his crowns but not the alveolar bone around his implants and teeth. (b) Radiograph of implants after being in bruxing function for over 20 years. (c and d) Clinical image and radiograph of patient’s TRINIA telescopic prosthesis.

The same process occurs with implants in the absence of peri-implantitis (periodontitis), as will be shown. Bone will adapt to the increased demands imposed upon it by an increased CIR within an acceptable range, the limits of which are not yet known. When that range is exceeded, there may be a material failure or bone fracture, but bone loss does not occur in the same sense as trauma from occlusion in the presence of periodontal disease. Anecdotal evidence has shown that Bicon implants cannot be overloaded after 5 years in function.

CIR and Bone Gain or Loss

The seemingly dramatic reverse CIR, which will be shown with short implants, is possible because, in a condition of health and within a given range, the bone is adaptable. Because the implant is not a tooth but an ankylosed structure,

if an implant restoration is properly designed, it is able to harmlessly distribute the large increases in occlusal stress associated with the use of short implants. In the absence of disease and with effective distribution, the forces of the increased CIR will not cause bone loss; the result will be either maintenance of homeostasis or bone gain. Implants are capable of generating bone loss under a variety of conditions, but increased CIR in the presence of an otherwise healthy mouth is not one of them. (Note that all CIRs in this chapter are ratios to 1.)

On the other hand, if an implant is carrying an excessive load in the presence of peri-implantitis, it will be subject to the type of bone loss associated with trauma from occlusion in the presence of periodontitis. The Bicon design has minimized an implant’s exposure to peri-implantitis by incorporating an implant-abutment interface (IAI) with no micromovement and so impermeable that not even the smallest periodontal pathogens have been able to infiltrate it (see chapter 6). That being said, it is time to consider the findings regarding CIR in greater detail, as well as other factors that influence bone levels around short implants.

The use of shorter implants invariably leads to increased CIRs. Established opinion holds that increasing the CIR will introduce significant moment arms on the implant and surrounding crestal bone when the implant restoration is subjected to lateral forces. Therefore, it has been suggested that excessive loads may cause peri-implant bone loss on splinted external hex dental implants; however, this is not true of all implants.[1] Fig 16-2 Single-implant restoration of a maxillary right lateral incisor that loosened during function. The statistical investigation suggests that the increased crown length played a significant role in the loosening of the implant; however, the trajectory of the implant and abutment should also be considered.

Fig 16-3 Four maxillary anterior teeth restored with 2.5-mm-well implants and abutments.

Fig 16-4 (a) A fractured 2.0-mm abutment after 22 years in function. (b) A new implant with a 3.0-mm post was used to replace it.

Because crestal bone stability is considered to be an indicator of the long-term success of dental implants, one of the most commonly used arguments against the use of short implants is that the increased occlusal forces, such as those produced by larger crowns supported by short implants, lead to crestal bone resorption. However, clinical research does not support this assertion.[2] In fact, a strong case can be made for the anabolic effect of increased forces on bone. It is well known that mechanical stimuli are critical for bone maintenance and repair and that maintaining bone mass requires a continuous, load-related osteoregulatory stimulus.[3–8] Moreover, crestal bone growth has been associated with increased loads in long-term follow-up studies of dental implants.[9,10] This is not remarkable, because bone adjusts to function.

It is seemingly intuitive that a longer dental implant should have a better prognosis because of its increased anchorage in bone. It is equally intuitive that the bone surrounding a smaller implant would be exposed to larger strains during mastication and would therefore have an uncertain prognosis. These reasonable intuitions fail to recognize two counterintuitive realities. The first is that bone is not monolithic; it is a living, dynamic tissue that changes its structure and size in response to the demands of its function. Because in the absence of disease, increased stress has an anabolic effect on bone up to the point at which it fractures, the ideal implant size should be the smallest possible size that can withstand masticatory forces without fracturing.[11,12] The second counterintuitive reality is that the established opinion regarding the CRR of teeth does not apply to implant CIR within a wide range of loads.[13]

This chapter represents decades of experiences of a group of implant clinicians and staff members at the Implant Dentistry Centre (IDC) in Boston, Massachusetts. Their clinical research and experience with short Bicon implants supports the assertion that the most common bone response to the increased stress of a longer crown on a shorter base is increased mineralization of the supporting bone. However, it is also known that excessive loads can lead to prosthetic complications, bone fracture, and loss of osseointegration. The following section is the group’s current understanding of a number of factors affecting periimplant bone levels around short implants.

The Effect of Increased CIR

A larger CIR has been found to be associated with an increase in prosthetic complications with 2.0- and 3.0-mmdiameter implant wells and abutment shafts for maxillary anterior freestanding implants. A retrospective investigation of 326 Bicon implants found that there was a statistically significant correlation between an increased CIR and the loosening of freestanding maxillary anterior abutments with 2.0- or 3.0mm diameters and the fracture of three abutments with 2.0mm shafts in the posterior mandible after years of function. The average CIR of the unsplinted maxillary anterior restorations that loosened was larger (2.01) than the average CIR of the restorations that remained stable (1.55) (Fig 16-2). There was also a statistically significant correlation between an increased CIR and the fracture of 2.0-mm-wide abutment shafts in posterior areas.[14] Three abutment shafts fractured in posterior areas, and the average CIR of these single-implant restorations was higher (1.47) than the average CIR of posterior restorations, also with 2.0-mm-wide abutment posts, that did not fracture (1.26).

These complications were managed by designing a more retentive abutment in 2010, an implant with a 2.5-mm well, for the maxillary anterior (Fig 16-3) and by revising the placement protocol to recommend the use of 3.0-mm abutment shafts for implants placed in posterior areas (Fig 16-4). Fig 16-5 (a) Preoperative radiograph. (b) An internal sinus elevation was necessary after extraction of the first molar prior to placement of a 4.5 × 8.0–mm implant and a titanium abutment. (c) Only 3 to 4 mm of the implant in was bone, which led to a CIR of 4 at crown placement. (d) Apical apposition of bone after 3 years of loading increased the effective implant length and reduced the CIR to 2.5, suggesting that the ideal implant length in this particular case would have been 6.0 mm.

Fig 16-6 Radiograph of a 4.5 × 6.0–mm implant restoring a maxillary first molar demonstrating bone mineralization toward the IAI 4 years after crown placement. The CIR was reduced over time because of bone growth. (a) Radiograph after placement with CIR of 2.6. (b) Radiograph 4 years later with CIR of 2.2.

Of greater interest was the finding that, contrary to expectations, there was no statistical significance between increases in a CIR as large as 4.95 and peri-implant bone loss surrounding Bicon implants. There was no deleterious effect on bone; in fact, in some instances the exact opposite occurred. As shown in the following treatments, the dynamism of the bone’s response was such that the increased CIR actually became smaller over time owing to bone growth in response to the resultant magnification of masticatory forces.

Bone Gain

Maxillary bone gain

In the treatment shown in Fig 16-5, recurrent caries led to extraction of the maxillary first molar (Figs 16-5a and 16-5b). For those unfamiliar with Bicon, current thinking in implant dentistry would consider the bony support shown in Fig 16-5c to be insufficient to support a first molar. Initially, this would seem to be a reasonable conclusion; however, after a period of dynamic response to the increased masticatory forces, coronal and apical apposition of bone resulted in a significantly reduced CIR (Fig 16-5d).

A similar result is seen in Fig 16-6, which clearly demonstrates how an increased CIR can have an anabolic effect in maxillary bone. Rather than inducing crestal bone loss, as prevailing opinion would have it, the apparently excessive loads actually induced bone growth around the implants.

Figure 16-7 reveals an obvious increase in bone density around a short implant after several years in function with a CIR of 3. A similar implant size and restorative approach led to a similar bone response around a maxillary posterior implant in the treatment shown in Fig 16-8. Figure 16-9 shows how after loading, the shorter 6.0-mm implant, carrying a clearly larger load, responded by developing greater bone density and height than the longer 8.0-mm implant.

Even in situations with less than 5.0 mm of available bone height, the placement of short implants in conjunction with an internal sinus elevation procedure can provide Fig 16-7 (a) Limited bone height and proximity to the maxillary sinus. (b) A 5.0 × 5.0–mm Bicon implant was used with a very limited internal sinus elevation at placement. (c) The implant was restored with an Integrated Abutment Crown (IAC) that was three times longer than the implant. (d and e) Increased bone density surrounding the implant was observed 4 years after crown placement. Fig 16-8 (a) A 2.5-mm Hand Reamer is used to corroborate the proximity to the sinus. (b) A 5.0 × 5.0–mm implant was placed at the same time an internal sinus elevation was performed. (c and d) Increased bone density is evident after 3 years of loading in this maxillary premolar area restored with a molar-sized crown. Fig 16-9 (a) There is 10.0 mm of bone height available in the maxillary left first molar site and significantly more bone available for the second premolar. (b) Two 5.0-mm-wide implants were placed and restored with IACs. The 6.0-mm-long implant was placed in the left first molar site, and the 8.0-mm-long implant was placed in the second premolar site. Similar crown heights but different implant lengths led to differing CIRs. (c) Clinical appearance. (d and e) The bone response after several years of loading suggests that the extra length used when restoring the premolar was unnecessary. Fig 16-10 (a) Because of the proximity to the maxillary sinus, the available bone height is only about 3 mm. (b) A floor transport sinus elevation procedure was performed at the same time a 6.0 × 5.7–mm implant was placed. Note that a Sinus Lift Abutment was used. (c) Note the lack of bone loss after 4 years of loading. a conservative treatment alternative to the more complex lateral sinus elevation. Figure 16-10 shows an increase in the mineralization of the surrounding bone 5 years after an internal sinus elevation and the placement of a short implant in less than 4.0 mm of bone height.

Another example can be seen where two short implants were used to treat a failing maxillary fixed prosthesis (Figs 16-11a to Fig 16-11k). Two bonded Integrated Abutment Crowns (IACs) simulated a three-unit fixed prosthesis. One IAC restored the first molar, and a second two-unit IAC with an angled abutment restored the two premolars. The two IACs were bonded together chairside with composite resin. Fig 16-11 (cont) (f and g) Verification of occlusal contacts approximately 1.5 years after crown placement. (h and i) Comparison of crestal bone stability surrounding the implant immediately upon placement of the two-unit fixed cantilever prosthesis and 3 years later. (j) Implant restorations after 1 year of loading. (k) Implant restorations after 3 years of loading. Fig 16-12 (a) Clinical image of mandibular right premolars restored with a two-unit IAC in which the first premolar is cantilevered mesially. (b) Radiograph on the day the prosthesis was placed. (c and d) Radiographs revealing not only the coronal composite veneer fracture, but more importantly the changes in bone height and density over 4.5 years of function.

Mandibular bone gain

Another counterintuitive result is shown in Fig 16-12, where a 4.5 × 6.0–mm implant is supporting two mandibular premolars, one of which is cantilevered mesially and demonstrates an increase in both bone height and density after

4.5 years of loading. Given what the maxillary examples have demonstrated, it is not surprising that there should also be bone gain in the mandibular arch. Conventional wisdom would have predicted bone loss or implant failure. The unexpected result was fracture of the veneered material and bone gain around the implant. Fig 16-13 (a and b) Radiographs revealing about 2 mm of implant length in bone, which was insufficient to withstand masticatory force. (c) Radiograph shows the implant was displaced into the sinus. Fig 16-14 (a) Radiograph revealing mesial peri-implant bone level on the day of crown and abutment placement. (b) Peri-implant bone growth after 2 years of function. (c) Peri-implant bone growth after 7 years of function. (d) Peri-implant bone gain after 13 years of function. (Reprinted with permission from Urdaneta et al.[20] )

Excessive Loading

Other treatments are shown that demonstrate that bone responds to excessive loading with fracture instead of crestal bone loss. Current thinking in implant dentistry includes what is presumed to be excessive loading as a possible cause of bone loss; however, in light of the opening comments and what has been presented, this seems unlikely.

It is well accepted that bone fractures in response to truly excessive forces; therefore, it is fair to question whether there is a limit, range, or threshold for bone to fracture surrounding dental implants.[15–18] What is the ideal amount of bone-to-implant contact that is necessary to withstand masticatory forces, and what is the ideal implant size? As shown in Figs 16-13a and 16-13b, only about 2 mm of the available implant length was within bone. This length, and the implant-to-bone contact it provided, proved to be insufficient to withstand the force necessary to seat the restoration, which is less than the usual forces of mastication (Fig 16-13c).

Bone Levels Surrounding SingleImplant Restorations

The dental implant literature has shown controversial findings with regard to the factors that significantly affect bone levels over time. The etiology of bone gain or loss after loading is not fully known. What is clear is that bone levels vary significantly between dissimilar implant designs.[19] Thus, the findings of a multicenter study that evaluated a particular implant design are not applicable to other implant systems and should not be extrapolated to serve as general guidelines. Consequently, for the purpose of this chapter, only research done on Bicon single-tooth implants restored with the load-bearing platform design is discussed.

Accordingly, having observed significant peri-implant bone growth surrounding Bicon implants after crown placement at the IDC, a retrospective investigation was designed.[20] During the clinical and radiographic evaluation, one treatment in particular made it clear that there had been a paradigm shift in implant dentistry. It was observed that over a period of 13 years, the bone surrounding a 6.0 × 8.0–mm implant with a Non-Shouldered Abutment had grown to the point that it was coronal to the IAI and was approaching the spherical base of the implant abutment (Fig 16-14). This clinical observation challenged everything that

Table 16-1 Multivariate statistical model on factors associated with peri-implant bone gain (Reprinted with permission from Urdaneta et al.[20] ) *Statistically significant ( P ≤ .05). CI, confidence interval; HA, hydroxyapatite; NSAIDs, nonsteroidal anti-inflammatory drugs.

had been taught and experienced with other implant designs. The prevailing theory was that all implants lost bone to the first thread after loading.

The retrospective investigation revealed statistically significant correlations between several local and systemic factors and changes in peri-implant bone levels, contributing to an understanding of the phenomenon of implant-related crestal bone growth. The investigation reported that 81 out of 326 implants (24.8%) showed varying degrees of apparent bone gain over time,[20] an experience that corroborated the findings of a previous investigation involving Bicon implants. Yoo et al[21] evaluated crestal bone levels adjacent to 347 immediately loaded Bicon implants and reported either no bone loss or crestal bone gain in 149 implants (32.2%).

Factors associated with bone gain

Of the 94 variables investigated, there were five local and systemic factors found to have a statistically significant association with peri-implant bone gain, including these three:

Factors associated with bone loss

The investigation also identified possible predictors of crestal bone loss after the placement of the definitive restoration. It was later learned that an implant restoration with a composite abutment base was significantly more likely to lose bone than those with a titanium base.[22] The research in two different patient cohorts also revealed a possible correlation between bone loss and smoking as well as mandibular location of the implant.[23,24]

To identify the factors that would continue to be correlated with peri-implant bone loss, a multivariate analysis was developed. Thirteen possible predictors for bone loss, together with biologically relevant factors of age and sex, were entered in a multivariate statistical model presented in Tables 16-1 to 16-3.[20] The multivariate model revealed four variables that were significantly correlated with peri-implant bone loss after placement of the definitive restoration:

1. Lack of a hydroxyapatite or calcium phosphate coating

2. Composite abutment base

3. Abutment design

4. Implant coating of calcium phosphate/hydroxyapatite (see later section)

5. Implant size

6. Daily intake of nonsteroidal anti-inflammatory medication (see later section)

7. The nonuse of nonsteroidal anti-inflammatory drugs

• (NSAIDs)

Table 16-2 Multivariate statistical analysis on factors associated with peri-implant bone loss[*] *Data from Urdanetce et al.[20] CI, confidence interval.

Descriptive statistics for predictor variables and univariate model for factors associated with changes in Table 16-3 peri-implant bone levels after the insertion of definitive restorations (continued)

(cont) Descriptive statistics for predictor variables and univariate model for factors associated with changes in Table 16-3 peri-implant bone levels after the insertion of definitive restorations (continued)

(cont) Descriptive statistics for predictor variables and univariate model for factors associated with changes in Table 16-3 peri-implant bone levels after the insertion of definitive restorations (continued)

(cont) Descriptive statistics for predictor variables and univariate model for factors associated with changes in Table 16-3 peri-implant bone levels after the insertion of definitive restorations (continued)

(cont) Descriptive statistics for predictor variables and univariate model for factors associated with changes in Table 16-3 peri-implant bone levels after the insertion of definitive restorations

Fig 16-15 (a) Peri-implant bone growth along the HA coating of the implant was documented. (b) Progressive bone gain was observed 2 years later. (c) Progressive bone gain was observed 8 years later.

Hydroxyapatite or Calcium Phosphate Coating

The presence of a hydroxyapatite (HA) or calcium phosphate (CP) coating was associated with a significant increase in peri-implant bone levels after crown placement. The presence of a titanium plasma spray surface treatment was correlated with bone loss, but under more specific conditions. The observation that HA- or CP-coated implants maintain osseous crest height and foster coronal apposition of bone is further supported by several animal studies.[22,25,26] The following clinical treatments support the above statements.

The bone response to an HA- or CP-coated implant in the absence of bacterial contamination is shown in Fig 16-15. Coronal apposition of bone was documented around the HA coating of a mandibular first molar restored with an IAC after several years of loading. Figure 16-16 demonstrates marked improvement in bone levels after several years of loading of a 5.0 × 6.0–mm short implant and a maxillary second molar IAC. The coronal apposition of bone observed on the distal of the implant defies the current understanding of implant dentistry, which would have predicted bone loss caused by what would be described as excessive loading.

It should be acknowledged that in some instances, if the hard and soft tissue can be predictably and economically restored, there may be benefits in terms of maintenance, plaque control, and aesthetics. Reduced bone height and width, particularly on the facial aspect, can lead to aesthetic limitations and contours that may contribute to plaque accumulation (Fig 16-17). On the other hand, even if it were possible to augment bone to improve the hard and soft tissue contours in the hope of reestablishing ideal soft tissue contours for aesthetic purposes, or even for improved maintenance, it is not worth the increase in the rate of complications and cost. Placing short implants with limited or no grafting in posterior areas and reinforcing oral hygiene provides a more predictable and more conservative approach.

Fig 16-16 Marked improvement in bone levels after 6 years of loading of a 5.0 × 6.0–mm short implant and a maxillary second molar IAC. (a) Radiograph taken immediately after loading. (b) Radiograph taken after 6 years of function. Fig 16-17 A clinical image of the second molar IAC.

a b a Fig 16-18 (a and b) A plateau-root form implant is seated without torque into a similar-sized osteotomy. Because only the tips of the fins contact the osteotomy, the HA coating between the plateaus cannot be damaged during implant placement.

HA or CP coatings with the Bicon design and placement technique

The Bicon design and its clinical techniques may also play an important role in the performance of the HA or CP coatings. It is reasonable to infer that the intracrestal placement of these implants protects them from bacterial contamination to some extent. This hypothesis was tested by Lee et al[27] when they evaluated the survival of 308 HA- or CP-coated Bicon implants, of which 167 were placed at the crest of the bone and 138 were placed 2.0 mm apical to the crest of the bone. They reported a statistically significantly higher survival rate for HA- or CP-coated implants when placed a minimum of 2.0 mm below the crest of bone (97% survival for implants placed below the crest vs 89.7% for implants placed at the crest).

It also seems reasonable to question whether the HA or CP coatings can be damaged during the torqueing or tightening of threaded implants. Unlike threaded implants, Bicon implants have a plateau design and are seated, rather than torqued, into their osteotomy. Only the tips of the plateaus contact the bone (Fig 16-18); therefore, the HA or CP coating of the plateaus of a Bicon implant are unlikely to be damaged during implant placement.

HA or CP coatings with internal sinus elevation

When placing maxillary posterior implants with limited bone height, it is difficult and sometimes impossible to obtain primary stability; however, with a Bicon implant, primary stability is not necessary, and even if only minimal stability can be achieved with an assist from a Sinus Lift Fig 16-19 (a) Radiograph showing bone levels insufficient to provide even the minimum primary stability required for threaded implants. (b) Radiograph taken upon placement of a short Bicon implant and Sinus Lift Abutment. (c) Six-month postoperative radiograph showing well-integrated implant and abutment. (d) Radiograph upon placement of an IAC. (e) Radiograph taken 2 years after placement of the IAC. Abutment and an HA or CP coating, the implant will successfully osseointegrate.

The following conservative treatment shows the placement of a short implant in conjunction with an internal sinus elevation and placement of SynthoGraft, a pure- phase beta-tricalcium phosphate material. The Sinus Lift Abutment was used to establish a minimal degree of stability and to prevent displacement of the implant into the sinus. Despite the obvious lack of primary stability that would be required for threaded implants, this implant integrated well and was restored successfully (Fig 16-19).

The literature has reported several advantages of HA- or CP-coated implants over uncoated implants.[28–33] Some of these advantages are increased bone-to-implant contact around coated implants when compared with uncoated implants, increased interfacial strength, more rapid adaptation of the coated implants to bone, and enhanced gap healing around coated implants.[28–33] Recently, studies have compared the healing around coated implants and implants with rough surface treatments.[34] These studies have reported a higher bone mineral apposition rate as well as a higher biomechanical fixation rate on HA- or CP-coated implants compared with implants with an alumina-blasted acid-etched titanium surface.[34]

Composite Abutment Bases

When a composite material was used by technicians to cover the titanium hemispheric base of the implant abutments, it was most often observed to be associated with significant peri-implant bone loss. The treatment depicted in Fig 16-20 is an example of the deleterious effect of covering the titanium base with a composite resin in an attempt to provide a more toothlike emergence profile. For some patients, it was possible to treat the bone loss by replacing the composite bases with titanium spherical bases, as shown in Fig 16-21, which depicts peri-implant bone mineralization under a titanium spherical base after 15 years of loading. Fig 16-20 (a and b) Radiographs showing the bone loss associated with covering the titanium hemispheric base with polyceramic composite in an attempt to provide a more tooth-like emergence profile. (c and d) Radiographs showing abutment after removal of polyceramic composite under the hemispheric titanium base. (e) Radiograph showing bone stability after more than 5 years of function after the removal of the polyceramic material. Fig 16-21 (a) Radiograph of an implant and IAC with a wide hemispheric abutment base. (b) Bone gain after 10 years in function. (c) Radiograph revealing bone gain after 15 years in function, giving credence to the fact that a wider abutment is more likely to foster bone gain.

Abutment Design

Titanium hemispheric base and load-bearing platform switching

We have reported peri-implant bone mineralization under the titanium spherical base of a Bicon abutment after several years of loading. The base of the Bicon titanium abutment transmits compressive loads to existing or potential bone coronal to the IAI; this concept is called load-bearing or bone-loading platform switching . The bone stability observed surrounding the Bicon implant may be the result of an implant design that efficiently distributes the forces of mastication and provides needed mechanical stimulation to the peri-implant bone. This is a new insight that replaces the prevailing idea that protecting bone from “excessive” masticatory loads is conducive to bone stability. In the absence of bacterially induced inflammation, and within an acceptable range yet to be determined, bone thrives in the presence of increasing functional loading and needs less protection than previously imagined.

Implant length and width

The literature has dedicated a significant amount of time to evaluating whether long or short implants have better survival and bone stability. Finite element stress analysis studies have reported that increasing the width is significantly Fig 16-22 (a) Radiograph of a 5.0 × 8.0–mm implant restoring a mandibular first molar at crown placement. The area below the fins or plateaus (in red ) represents the implant’s effective length, the surface area that actively participates in distributing compressive forces (blue arrow) to bone. (b) Crestal bone mineralization after 8 years of loading. Fig 16-23 Radiographs showing crestal bone growth throughout 8 years of implant loading in a patient taking a daily dose of an NSAID. (a) Radiograph after placement of the IAC. (b) Radiograph 8 years later. (Reprinted with permission from Urdaneta et al.[20] )

more useful for stress reduction through effective stress distribution than increasing the length of an implant.[35–37] Because longer implants require more complex surgical procedures, the ideal implant size should be the smallest possible implant size capable of withstanding masticatory forces while ensuring bone stability or bone growth. A 5.0 × 8.0–mm implant is significantly more likely to gain bone than a 5.0 × 11.0–mm implant, which is significantly more likely to lose bone (see multivariate analysis in Table 16-3).

The fact that 5.0 × 8.0–mm implants in the mandible outperformed similar implants in the maxilla suggests that there is an optimum strain environment for bone in different areas of the mouth and that there may be an ideal implant size to restore each clinical situation. This is consistent with the results of previous studies demonstrating that the peak strains innate for each anatomical area should be maintained to optimize the response of the bone.[38]

Surface area and stress

An increase in mechanical usage is known to increase bone deposits.[39] Frost presented the concept of a minimum effective strain (MES) for bone modeling as in the range of 1,500 to 2,500 microstrains and reported that strains above the MES led cortical bone to change its mass and architecture. Therefore, it is possible that the magnitude of stress produced by masticatory forces in the posterior mandible is distributed around a 5.0 × 8.0–mm Bicon implant so that the maximum volume of bone in contact with the implant will be loaded at or higher than the MES, leading to positive bone remodeling. This remodeling would be observed as a gain in both density and height of the crestal bone.

However, only the functional surface area (ie, the area that actively serves to dissipate compressive and tensile nonshear loads through the implant-to-bone interface) should be considered.[40] Of the total surface area of the 5.0 × 8.0–mm Bicon implant, only the area on the underside of each of the ten fins or plateaus of the implant serves to dissipate direct vertical compressive forces on bone and thus should be considered its effective length (Fig 16-22). However, in the matter of lateral loading of the implant, both the inferior and superior surfaces of the plateaus serve to dissipate the compressive forces, which explains why Bicon implants function so well with lateral loads.

NSAIDs

In addition to the foregoing, a retrospective clinical investigation also reported that the daily intake of NSAIDs has an association with crestal bone growth after crown placement.[20] While the full text of the discussion and methodology of that study is available, what follows are the images associated with those issues, along with a brief description.

The radiographs presented in Fig 16-23 demonstrate crestal bone growth after crown placement in patients taking daily doses of NSAIDs (eg, aspirin, ibuprofen, celecoxib) for cardiovascular reasons or arthritic pain control. The positive effect of NSAIDs on the crestal bone levels around implants may be attributed to their inhibition of the synthesis of prostaglandins (PG), resulting in a reduction of PG levels in the tissues surrounding the implants. The patient shown previously in Fig 16-14 was also reported to have been taking 1,600 mg of ibuprofen daily for arthritic pain control. Fig 16-24 (a and b) Radiographs taken 3 years apart showing the opening of the interproximal contact between two mandibular posterior IACs. (c) Radiograph 1 year later showing the open interproximal contact. (d) Radiograph showing the removal of the first molar IAC to close the open interproximal contact and peri-implant bone loss. (e) Radiograph showing the closed interproximal contact and the replacement restoration. (f) Radiograph showing bone growth 3 months after replacing the restoration. (g) Radiograph showing bone growth after 2 years of function with the replacement restoration. (Reprinted with permission from Urdaneta et al.[20] )

Five months after the treatment of a 47-year-old man with an open interproximal contact between two mandibular posterior IACs, the first molar IAC was removed, and the open contact was closed. Peri-implant bone loss was evident at that time. The bone loss was successfully treated with replacement of the restoration and administration of topical and systemic antibiotics in addition to systemic NSAIDs (Fig 16-24).

Figure 16-25 reflects the 3-year implant treatment history of a 68-year-old man who had a fractured mandibular right second premolar extracted (Figs 16-25a and 16-25b). After 2 months, the missing tooth was replaced with a 4.5 × 6.0– mm implant (Fig 16-25c). The implant was restored with an IAC 3 months after placement (Fig 16-25d). One year later, suppuration was noted clinically, and a radiograph revealed peri-implant bone loss (Fig 16-25e). The implant surface was cleaned and treated with a laser. The immediate infection was treated with amoxicillin 500 mg three times a day for 10 days and a local application of minocycline hydrochloride. During the 6 months following initial treatment, the patient was instructed to take 81 mg of aspirin and 1,000 mg omega-3acid ethyl esters daily. Gradual remineralization of the bone surrounding the implant was documented at intervals of 3, 4, and 9 months (Figs 16-25f to 16-25h). After 16 months of treatment, the substantial increase in bone mineralization and volume was evident (Fig 16-25i). Fig 16-25 (a and b) Radiographs before and after the extraction of a fractured mandibular right second premolar. (c) Radiograph after implant placement. (d) Radiograph 2 months after the IAC placement. (e) Radiograph 1 year later, revealing peri-implant bone loss. (f to h) Gradual remineralization shown in radiographs throughout a 9-month period. (i) Radiograph showing bone gain 16 months after treatment for the peri-implant bone loss.

Conclusion

It is clear that contrary to historical thinking, it should not be assumed that all implants routinely lose bone to their first thread. Further, it has been shown that the use of short implants are not only a feasible option but clearly the best option. Finally, it has been shown repeatedly that a Bicon implant is more likely to not only maintain its original bone levels over years of function but will often increase the level of bone above its IAI with an increase in density and mineralization of the surrounding bone.

Many of the findings and discussions of this chapter have come from a retrospective study. The strength of the study’s data is the fact that more than 90 different possible variables were thoroughly investigated. The most significant limitations of the study include the fact that the data were obtained from only one clinical center, its sample size, and its retrospective design. These factors limit the capacity to extrapolate this information and make generalizations; however, the results speak for themselves.

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4. Lanyon LE. Using functional loading to influence bone mass and architecture: Objectives, mechanisms, and relationship with estrogen of the mechanically adaptive process in bone. Bone 1996;18(suppl 1):37S–43S.

5. Frost HM. The mechanostat: A proposed pathogenic mechanism of osteoporoses and the bone mass effects of mechanical and nonmechanical agents. Bone Miner 1987;2:73–85.

6. Turner CH, Warden SJ, Bellido T, et al. Mechanobiology of the skeleton. Sci Signal 2009;2:pt3.

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8. Van der Meulen MCH, Yang X, Morgan TG, Bostrom MPG. The effects of loading on cancellous bone in the rabbit. Clin Orthop Relat Res 2009;467:2000–2006.

9. Dhima M, Balshi T, Wolfinger G, Petropoulos VC, Balshi S. A retrospective analysis of mandibular bone height changes associated with 81 screw-retained implant-supported prostheses with distal cantilevers: A long-term follow-up analysis. Int J Oral Maxillofac Implants 2013;28:854–859.

10. Roberts RA. A 24-year retrospective study of bone growth after implant placement. J Oral Implantol 2005;31:98–103.

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12. Pistilli R, Felice P, Cannizzaro G, et al. Posterior atrophic jaws rehabilitated with prostheses supported by 6 mm long 4 mm wide implants or by longer implants in augmented bone. One-year post-loading results from a pilot randomised controlled trial. Eur J Oral Implantol 2013;6:359–372.

13. Birdi H, Schulte J, Kovacs A, Weed M, Chuang SK. Crown-to-implant ratios of short-length implants. J Oral Implantol 2010;36:425–433.

14. Urdaneta RA, Rodriguez S, McNeil DC, Weed M, Chuang SK. The effect of increased crown-to-implant ratio on single-tooth locking-taper implants. Int J Oral Maxillofac Implants 2010;25:729–743.

15. Martin AD, McCulloch RG. Bone dynamics: Stress, strain and fracture. J Sports Sci 1987;5:155–163.

16. Zadpoor AA, Nikooyan AA. The relationship between lower-extremity stress fractures and the ground reaction force: A systematic review. Clin Biomech (Bristol, Avon) 2011;26:23–28.

17. Kaeding CC, Najarian RG. Stress fractures: Classification and management. Phys Sportsmed 2010;38:45–54.

18. McCormick F, Nwachukwu BU, Provencher MT. Stress fractures in runners. Clin Sports Med 2012;31:291–306.

19. Laurell L, Lundgren D. Marginal bone level changes at dental implants after 5 years in function: A meta-analysis. Clin Implant Dent Relat Res 2011;13:19–28.

20. Urdaneta RA, Daher S, Leary J, Emanuel K, Chuang SK. Factors associated with crestal bone gain on single-tooth locking-taper implants: The effect of nonsteroidal anti-inflammatory drugs. Int J Oral Maxillofac Implants 2011;26:1063–1078.

21. Yoo RH, Chuang SK, Erakat MS, Weed M, Dodson TB. Changes in crestal bone levels for immediately loaded implants. Int J Oral Maxillofac Implants 2006;21:253–261.

22. Kohri M, Cooper EP, Ferracane JL, Waite DF. Comparative study of hydroxyapatite and titanium dental implants in dogs. J Oral Maxillofac Surg 1990;48:1265–1273.

23. Urdaneta RA, Leary J, Panetta KM, Chuang SK. The effect of opposing structures, natural teeth vs. implants on crestal bone levels surrounding single-tooth implants. Clin Oral Implants Res 2014;25:e179–e188.

24. Urdaneta RA, Seemann R, Dragan IF, Lubelski W, Leary J, Chuang SK. A retrospective radiographic study on the effect of natural tooth-implant proximity and an introduction to the concept of a bone-loading platform switch. Int J Oral Maxillofac Implants 2014;29:1412–1424.

25. Ong JL, Chan DCN. Hydroxyapatite and their use as coatings in dental implants: A review. Crit Rev Biomed Eng 2000;28:667–707.

26. Pilliar RM, Deporter DA, Watson PA, et al. The effect of partial coating with hydroxyapatite on bone remodeling in relation to porous-coated titanium-alloy dental implants in the dog. J Dent Res 1991;70:1338–1345.

27. Lee EH, Ryu SM, Kim JY, et al. Effects of installation depth on survival of an hydroxyapatite-coated Bicon implant for single-tooth restoration. J Oral Maxillofac Surg 2010;68:1345–1352.

28. Meffert RM, Block MS, Kent JN. What is osseointegration? Int J Periodontics Restorative Dent 1987;7(4):9–21.

29. Gottlander M, Albrektsson T. Histomorphometric analyses of hydroxyapatite-coated and uncoated titanium implants. The importance of the implant design. Clin Oral Implants Res 1992;3:71–76.

30. Carr AB, Larsen PE, Papazoglou E, McGlumphy E. Reverse torque failure of screw-shaped implants in baboons: Baseline data for abutment torque application. Int J Oral Maxillofac Implants 1995;10:167–174.

31. Bell R, Beirne OR. Effect of hydroxylapatite, tricalcium phosphate, and collagen on the healing of defects in the rat mandible. J Oral Maxillofac Surg 1988;46:589–594.

32. Geesink RG, de Groot K, Klein CP. Bonding of bone to apatite-coated implants. J Bone Joint Surg Br 1988;70:17–22.

33. Oonishi H, Yamamoto M, Ishimaru H, et al. The effect of hydroxyapatite coating on bone growth into porous titanium alloy implants. J Bone Joint Surg Br 1989;71:213–216.

34. Coelho PG, Freire JN, Granato R, et al. Bone mineral apposition rates at early implantation times around differently prepared titanium surfaces: A study in beagle dogs. Int J Oral Maxillofac Implants 2011;26:63–69.

35. Petrie CS, Williams JL. Comparative evaluation of implant designs: Influence of diameter, length, and taper on strains in the alveolar crest. A three-dimensional finite-element analysis. Clin Oral Implants Res 2005;16:486–494.

36. Himmlová L, Dostálová T, Kácovský A, Konvicková S. Influence of implant length and diameter on stress distribution: A finite element analysis. J Prosthet Dent 2004;91:20–25.

37. Ding X, Liao SH, Zhu XH, Zhang XH, Zhang L. Effect of diameter and length on stress distribution of the alveolar crest around immediate loading implants. Clin Implant Dent Relat Res 2009;11:279–287.

38. Blanes RJ, Bernard JP, Blanes ZM, Belser UC. A 10-year prospective study of ITI dental implants placed in the posterior region. I: Clinical and radiographic results. Clin Oral Implants Res 2007;18:699–706.

39. Misch C, Bidez MW. A scientific rationale for dental implant design. In: Misch C (ed). Implant Dentistry, ed 2. St. Louis: Mosby, 1999.

40. Rubin CT, Lanyon LE. Regulation of bone formation by applied dynamic loads. J Bone Joint Surg Am 1984;66:397–402.

17

Implant Placement in Compromised Tissue

Rolf Ewers | Vincent J. Morgan | Dusan Poruban | Paolo Perpetuini | Olga Davydova | Alexey Davydov | Igor Kostin | Stan Politis

Some of the most difficult clinical scenarios in implant dentistry are those involving compromised bone and soft tissue. This chapter presents a series of such scenarios and their seemingly difficult treatments. In many cases, even the most challenging clinical situations became manageable and were facilitated because of the clinical capabilities of Bicon implants and the computer-aided design/computer-assisted manufacturing (CAD/CAM) restorative material TRINIA.

Ameloblastoma

Treatment 1

The first treatment demonstrates the prosthetic restoration and 23-year follow-up of six Bicon implants placed in the mandibular iliac crest graft of a 55-year-old woman. Her mandible had been resected due to an ameloblastoma 2 years prior to placement of the implants. Radiographs show her surgical treatments prior to implant placement (Figs 17-1a to 17-1d). Four months after placement of the implants and prior to their prosthetic restoration, a full-thickness flap was reflected, revealing the six black polyethylene Healing Plugs—some of which were covered with newly generated bone (Figs 17-1e and 17-1f). Subsequently, 10.0-mm-long NonShouldered Abutments were placed into the wells of the implants (Fig 17-1g).

Following a period of initial healing, a mucoplasty was performed to excise an excessive amount of unattached soft tissue that was interfering with restoration of the abutments (Fig 17-1h). A pink denture resin wafer was fabricated over the abutments to stabilize a periodontal dressing (Figs 17-1i to 17-1l). Fig 17-1 (a) Preoperative radiograph of the ameloblastoma lesion. (b) Cone beam computed tomography scan of ameloblastoma lesion. (c) Postoperative radiograph of mandibular resection with extraoral fixation. (d) Postoperative radiograph of titanium crib and iliac crest bone graft. (e) Postoperative radiograph of six Bicon implants. Note the level of bone and the fact that the implants are entirely apical to the adjacent teeth. (f) Black Healing Plugs at implant uncovering. (g) Six permanent Non-Shouldered Abutments in place. Note that the coronal aspect of the 10.0-mm abutment is apical to the crown of the adjacent tooth. (h) Excessive soft tissue healing around the six abutments. Soft tissue will be excised to the level of the periosteum. (i) Wafer of acrylic being formed. This will act as a postoperative splint dressing for the 2 weeks of soft tissue healing. (j) Trimming of acrylic wafer. (k) Intraoral try-in of the polished acrylic wafer. (l) The periodontal dressing is sandwiched in place with the acrylic wafer, providing immobility for soft tissue healing.

Two weeks later, a provisional restoration was created through the modification of the patient’s existing removable denture (Figs 17-1m and 17-1n). Subsequently, a fullarch impression was made, and after some of the stone dies were modified to achieve a path of insertion, a gold alloy casting was fabricated on a dental stone model (Fig 17-1o). Red acrylic corrective copings were fabricated over the modified dies to facilitate nonverbal communication between the technician and dentist (Fig 17-1p); the copings were used to show the dentist how to accomplish the necessary adjustment of the Non-Shouldered Abutments prior to the placement of the gold alloy frame (Figs 17-1q and 17-1r). A red dental resin attached to the framework was used to record the positional relationship of the two arches (Fig 17-1s). Clinical and radiographic images were taken on the day the definitive restoration was placed (Figs 17-1t to 17-1v).

An image of the soft tissues taken 7 years after the prosthesis was placed reveals an excellent clinical result for this patient Fig 17-1 (cont) (m) At the first restorative appointment, a transitional prosthesis is provided by relining the patient’s existing prosthesis. (n) After making a full-arch hydrocolloid impression and an occlusal registration, the relined existing prosthesis was placed. (o) Stone dies were modified. (p) Corrective copings on abutments. (q) At the second restorative visit, the abutments were modified through corrective copings with a carbide bur. (r) Gold framework on stone model. (s) Occlusal registration was taken with the framework in place. (t) Porcelain-fused-to-metal (PFM) restoration. (u) At the third restorative visit, the restoration was placed onto the six Bicon Non-Shouldered Abutments without cement. (v) Postplacement radiograph. (w) Seven-year postoperative view of the soft tissues around implant abutments. Despite the fact that there was no attached tissue, there has never been any peri-implantitis nor bone loss. (x) Seven-year follow-up radiograph. Note the bone level and the fact that the implants are entirely apical to the adjacent teeth. —— ,

(Fig 17-1w), even with the marginal chipping of the porcelain. This chipping may have been avoided had the prosthesis been fabricated with a broad metal margin, especially since it was used as a telescopic restoration. The first evidence of minor bone loss around the most posterior abutment appeared 14 years after the implants were placed and was associated with ineffective plaque control (Figs 17-1x to 17-1z).

During a maintenance visit 23 years after the prosthesis was placed, clinical images revealed a remarkable level of clinical health of the mucosa around implants, particularly in consideration of a total absence of attached mucosa at the outset of treatment. The telescopic prosthesis held up remarkably well, even with the chipping of the marginal porcelain. The most compelling evidence of success is in the radiographic and clinical images revealing healthy mucosa and excellent bone levels around the implants after being in function for 23 years (Figs 17-1aa and 17-1bb). Fig 17-1 (cont) (y) A significant deposit of calculus at the 14-year postoperative visit indicating poor hygiene. (z) Fourteen-year postoperative radiograph reveals first evidence of minimal bone loss around the most distal implant. (aa) Postoperative radiograph after 23 years of function. (bb) Postoperative clinical image of the PFM telescopic prosthesis, which continues to function very well despite the marginal chipping of porcelain. Fig 17-2 (a) A 35-year-old man with epidermolysis bullosa. (b) Radiograph showing class VI atrophic maxilla with two implants.

Epidermolysis Bullosa

So-called “butterfly children,” or children with inherited connective tissue disease, have a relatively short life expectancy, and any of their surgical treatments are very difficult to manage. As addressed by Beikler and Flemmig,[1] there are few reports in the literature about the use of implants in this medically compromised class of patients. In treating these patients, the degree of systemic disease control may be more important than the nature of the disorder itself, and individualized medical control should be established prior to any implant therapy. However, for patients with this disorder, the quality of life and functional benefits from dental implants may outweigh any risks.[2]

Treatment 2

Encouraged by positive reports regarding the possibility of success in the treatment of this group, a 35-year-old man suffering from dystrophic epidermolysis bullosa was treated with four Bicon implants at the Catholic University of Leuven in Belgium[3–5] (Fig 17-2a). Prior to this, he had received four Ankylos (Dentsply) implants in his maxilla, two of which were lost within a month. The radiographs revealed an extremely atrophied class VI maxilla despite his young age[6] (Figs 17-2b and 17-2c).

As expected, his skin as well as his mucosa was severely compromised; it was very loose and not fixed to the underlying tissue (Fig 17-2d). During the operation, one of the left Ankylos implants was found to be loose, and it was removed. Enough bone remained on the left side of his maxilla to place one 3.0 × 8.0–mm and one 4.0 × 5.0–mm Bicon implant (Fig 17-2e). Fig 17-2 (cont) (c) Reformatted orthoradial slice of a dental CT showing the maxilla with one integrated and one nonintegrated implant. (d) Intraoral view of the patient’s very friable mucosa. (e) Radiograph after removal of nonintegrated Ankylos implant and placement of a 3.0 × 8.0–mm and a 4.0 × 5.0–mm Bicon implant in the left maxilla. (f) Radiograph after placing two additional 3.0 × 8.0–mm Bicon implants in the right maxilla. (g) Intraoral view of the primarily healed mucosa 10 days after placing the implants and before suture removal. (h) Facial view of wax teeth arrangement in occlusion. (i) Trajectories of four guide pins in implant analogs within the stone model. (j) Intaglio view of the maxillary TRINIA prosthesis with four grit-blasted abutments. (k) A light-cured resin seating jig was used to orient and initially seat the four abutments. —_>

Fortunately, the patient’s healing was completely uneventful, so 2 months later, two 3.0 × 8.0–mm Bicon implants were placed in the right maxilla (Fig 17-2f). Once again, there was uneventful primary mucosal healing (Fig 17-2g).

Three and a half months later, the four implants were uncovered, and a full-arch, implant-level transfer impression and occlusal registration were made (Fig 17-2h). The prosthetic aspects of his treatment were especially difficult because of the labial angulation of the implants (Fig 17-2i).

To facilitate the placement of the abutments, a custommade localization jig was used (Figs 17-2j and 17-2k). These procedures were performed with local anesthesia, and even the mild trauma associated with the injections caused large hematomas and a separation of the mucosa from the underlying tissue (Fig 17-2l); however, the final occlusion and the patient’s smile were very satisfying and justified his treatment (Fig 17-2m). The panoramic radiograph also reveals an excellent result (Fig 17-2n). Fig 17-2 (cont) (l) Palatal view of the definitively seated abutments and hematomas and loosening of the mucosa of the underlying tissue caused by local anesthesia injections. (m) Patient’s smile after placement of the full-arch TRINIA prosthesis. (n) Radiograph after placement of the full-arch TRINIA prosthesis.

implant was placed in the site of the maxillary right lateral incisor, a 3.5 × 8.0–mm implant was placed in the site of the maxillary left lateral incisor, and a 4.0 × 5.0–mm implant was placed in each maxillary tuberosity (Fig 17-3b).

After 6 months of healing, the implants were uncovered and later restored with a TRINIA full-arch prosthesis (Figs 17-3c to 17-3f). The postoperative radiographic image showed a satisfactory outcome (Fig 17-3g).

Type 2 Diabetes Mellitus

Systematic reviews and meta-analyses have been used to determine whether type 2 diabetes mellitus has any effect on the rates of implant failures, postoperative infections, and marginal bone loss. The findings revealed that there were no significant differences in the rates of implant failures between diabetic and nondiabetic patients.[7] Many authors agree that patients with diabetes can receive implant-based treatments safely, provided they have moderate hemoglobin A1c (HbA1c) values.[8,9]

Bone Marrow Transplantation

Hematopoietic stem cell transplantation (HSCT) patients have a high incidence of long-term adverse effects, with 93% of survivors having at least one late adverse effect after 7 years of follow-up. For this reason, HSCT survivors require lifelong close screening and monitoring.[10–12] Because of these risks, it is very difficult to decide whether these patients should be treated with dental implants, and unfortunately, the literature about these treatments is very sparse.[13]

Treatment 3

Treatment 4

This case describes the successful treatment of a 64-year-old patient with a 20-year history of type 2 diabetes mellitus, an HbA1c level under 6, and an extreme class VI Cawood and Howell[6] maxillary atrophy (Fig 17-3a). A decision was made to use narrow and short Bicon implants. A 3.0 × 8.0–mm

This section describes the treatment of a 54-year-old woman who had undergone HSCT 2 years prior to a 4-year regimen of bisphosphonate therapy, during which time she was without symptoms. The result of a C-terminal cross-linking telopeptide test was 570 pg/mL, a positive value far above Fig 17-3 (a) Radiograph of a 64-year-old patient with extreme class VI maxillary atrophy. (b) Radiograph of 4.0 × 5.0–mm, 3.0 × 8.0–mm, and 3.5 × 8.0–mm Bicon implants. (c) Palatal view of TRINIA prosthesis on stone model. (d) Intaglio view of TRINIA prosthesis. (e) Palatal view of four definitively seated abutments. (f) View of cemented TRINIA prosthesis. (g) Radiograph of cemented TRINIA prosthesis.

the risk zone.[14] Although she was a high-risk patient, it was decided to proceed with implants based upon the excellent hard and soft tissue response that had been seen with previous Bicon implant placements.

Initially, the remnants of the mandibular right lateral incisor, right central incisor, and left lateral incisor were removed, and the alveolar crest of the very atrophic mandible was shortened, changing its classification from a Cawood and Howell[6] class V to a class VI atrophic jaw, especially on her left side (Fig 17-4a). Eight weeks later, after a period of uneventful wound healing, four 4.0 × 5.0–mm short Bicon implants were placed in the interforaminal area (Figs 17-4b and 17-4c).

At the time of uncovering, after 3 months of healing, the implants were partially covered with new bone (Fig 17-4d). Using the same-size Sulcus Former as the intended abutment, the bone covering the implant was shaped so that the chosen abutment would have sufficient space to fit into the implant well (Fig 17-4e). After inserting 2.5-mm Impression Posts into the implant wells, the wound was closed with resorbable single-knot sutures (Fig 17-4f). The 2.5-mm acrylic impression sleeves were snapped onto their corresponding impression posts in preparation for a full-arch implant-level transfer impression (Fig 17-4g).

Subsequently, a wax try-in prosthesis mounted on a TRINIA prosthetic base was evaluated (Figs 17-4h and 17-4i). The try-in revealed that the occlusion was inadequate, so another bite registration was recorded, and another try-in was made. The second try-in was successful, and the definitive full-arch TRINIA prosthesis was delivered to the patient (Figs 17-4j to 17-4l). The 2-year recall panoramic radiograph shows the excellent result of this challenging treatment (Fig 17-4m). Fig 17-4 (a) Radiograph of a 54-year-old woman with a few teeth in a very atrophic mandible, class V to VI, especially in the left molar region. (b) The last of four 4.0 × 5.0–mm implants with 2.5-mm wells being placed into its osteotomy and three blue 2.5-mm guide pins indicating the trajectories of three implants in situ. (c) Radiograph of four 4.0 × 5.0–mm Bicon implants. (d) View of implants being uncovered. (e) A gold 5.0-mm Sulcus Former being used to shape the tissues to conform to the intended abutments. (f) Four blue 2.5-mm titanium impression posts with sutured mucosa. (g) Four acrylic impression sleeves on their corresponding posts. (h) Intaglio of wax teeth arrangement with two impression posts to facilitate stabilization of the rim. (i) View of waxed teeth arrangement. (j) Intaglio view of the mandibular TRINIA prosthesis with four abutments. (k) View of four definitively seated abutments. (l) View of cemented TRINIA prosthesis. (m) Radiograph of TRINIA prosthesis at the 2-year recall. Fig 17-5 (a) Radiograph of a 59-year-old woman with an edentulous left maxilla distal to her carious lateral incisor. (b) Surgical site after extraction of lateral incisor and necrosectomy. (c) View of the maxillary ridge with three implants. (d) Radiograph of one 4.0 × 5.0–mm and two 3.5 × 8.0–mm implants. (e) Uncovering of anterior implant. Note that the Healing Plug is completely covered with new bone. (f) Implant with black Healing Plug is visible after the removal of newly formed bone from over the implant. (g) Round bur is used to remove bone covering the two posterior implants. (h) View prior to the uncovering of the most posterior implant. (i) View of Sulcus Former, attached to a threaded knob, being used to remove bone around the anterior implant to form a sulcus to conform to the shape of the intended abutment. Red and blue impression posts are visible in the posterior implants. —_

Denosumab Therapy

Treatment 5

This treatment is an example of the occurrence of druginduced osteonecrosis of the jaws (DIONJ) after use of denosumab, a new generation of osteoclast-inhibiting medication.[15,16] For this patient, as for others, the bone necrosis was treated with primary curettage surgery followed by the placement of Bicon implants. A 59-year-old woman who had been undergoing denosumab therapy for the past 2 years presented with a massive purulent periapical periodontitis following the fracture of her maxillary left lateral incisor. Her left posterior maxilla was edentulous (Fig 17-5a). With a full understanding of the risks associated with denosumab therapy, the patient remained determined to have implants to replace her missing dentition. Following the extraction of her fractured lateral incisor and thorough surgical curettage of the necrotic bone, two 3.5 × 8.0–mm implants and one 4.0 × 5.0–mm short Bicon implant were placed (Figs 17-5b to 17-5d). Because of the extent of the defect associated with the extracted lateral incisor as seen on the panoramic radiograph, the implants had to be placed a little deeper than usual.

Seven months later, the implants were uncovered. The implants in both the extraction site and in the tuberosity were completely covered with newly formed bone that had to be removed with a round bur (Figs 17-5e to 17-5h). In addition to removal of the overlying bone, a Sulcus Former corresponding in size to the base of the intended abutment was used to remove bone around the head of the implant. Its use is essential to ensure the definitive seating of the abutment and the subsequent engagement of the locking-taper abutment (Fig 17-5i). Fig 17-5 (cont) (j) Red and blue Impression Posts with corresponding acrylic sleeves for the making of an implant-level impression. (k) Five-unit TRINIA prosthesis with three abutments. (l) Radiograph of cemented TRINIA prosthesis at 2-year recall.

After inserting the Impression Posts and their corresponding acrylic sleeves, a full-arch implant-level impression was made (Fig 17-5j). A five-unit TRINIA prosthesis was fabricated and cemented in place (Fig 17-5k). The results were very satisfactory, as evidenced by the 2-year postoperative radiograph (Fig 17-5l).

Bisphosphonate Therapy

Since its first textbook identification in 2002 and its first appearance in a journal publication in 2003, bisphosphonate-induced osteonecrosis of the jaws, now more widely referred to as DIONJ, has not only been occurring but increasing in the number of clinical cases being reported.[17–22] The new commercial bisphosphonate drugs, including two commercial denosumab drugs, have caused DIONJ and have added further uncertainty concerning the prevention, management, and resolution-directed treatment for osteoporosis.[23–25] There are many benefits of the Bicon system for clinicians and patients to appreciate, but the bacterially sealed locking-taper implant-abutment interface (IAI) is paramount in minimizing the flow of subgingival organisms that potentially contribute to the increasing threat of DIONJ.[26]

canine and lateral incisor were removed, as well as the necrotic bone around them, and the defect was closed using a mucoperiosteal pedicle flap (envelope flap) with a double-layer closure (Fig 17-6c).

Fortunately, primary wound healing was uneventful, and 3 months later, a 3.5 × 8.0–mm Bicon implant was placed in the site of the right lateral incisor and a narrow 3.0 × 8.0– mm Bicon implant in the site of the right canine (Figs 17-6d to 17-6g). The two implants had to be angled parallel to the palatal cortical bone because of the defect in the buccal bone, although this is not clearly shown in the postoperative panoramic radiograph (Fig 17-6h).

After 6 months, the implants were uncovered, and a full-arch implant-level transfer impression and bite registration were made (Fig 17-6i). Subsequently, two crowns with seemingly unfavorable abutment angulations were placed to the patient’s satisfaction (Figs 17-6j and 17-6k). The 2.5-year radiograph revealed very satisfactory results, and there were no signs of peri-implantitis or osteonecrosis (Fig 17-6l).

Bilateral Cleft Palate

Treatment 7

Treatment 6

The next treatment was for an 84-year-old woman who presented with DIONJ. She had been medicated with Fosamax (Merck) for 8 years. Eleven years before she had developed the osteonecrosis, she had had two 3.8 × 13.0–mm XiVE (Dentsply) implants placed in the sites of the maxillary right first molar and second premolar. Five years later, a 4.3 × 13.0–mm CAMLOG implant was placed in the site of the right first premolar.

There had been no problems during the first 8 years of her Fosamax therapy; however, shortly after the 8th year, a purulent infection involving the maxillary right canine and lateral incisor developed, with sequestered bone perforating the buccal mucosa (Figs 17-6a and 17-6b). The right

A 20-year-old woman presented for treatment of two maxillary bone defects secondary to a bilateral cleft palate. Her past medical history was noncontributory, and she reported no lifestyle risk factors. Though there were bilateral soft tissue invaginations into the defects, the cone beam computed tomography (CBCT) scan showed there was no oronasal communication (Fig 17-7a). In spite of the former existence of a bilateral total lip and cleft palate, there were slight cicatrices observed at the top of the frontal maxillary vestibulum and the lip (Fig 17-7b). Despite the presence of a fixed orthodontic device, her anterior maxilla could be moved with pressure. Her CBCT scan revealed a small segment of bone in the midline of her palate. Using a Khoury trephine technique, two autogenous free bone grafts were taken bilaterally from her mental regions to augment her two maxillary defects. Bilateral soft tissue mucogingival transposition flaps served to cover the transplant areas (Figs 17-7c and 17-7d). There were minor postoperative complications on her left side in the form of occasional sequestrations of bony transplant chips. Fig 17-6 (a) Clinical view of bone sequestra in an 84-year-old woman with DIONJ. (b) Radiograph of osteonecrotic bone in the region of the maxillary right canine and lateral incisor. (c) Double-layer closure before suture removal. (d) Uneventfully healed wound. (e) A 3.5 × 8.0–mm implant with a 2.0-mm well being placed into its osteotomy. (f) View of two seated implants with their cut polyethylene Healing Plugs. (g) Harvested bone placed over the seated implants. (h) Radiograph of one 3.5 × 8.0–mm and one 3.0 × 8.0–mm implant. (i) Red 2.0-mm titanium Impression Posts with corresponding acrylic sleeves for the making of a full-arch implant-level impression and a bite registration. (j) Facial view of abutments seated at a seemingly unfavorable angle. (k) Facial view of cemented prosthesis. (l) Radiograph at 2.5-year recall.

After approximately 2 months without a sequestration, a 4.0 × 6.0–mm implant with a 2.5-mm well diameter was placed in the site of her maxillary left lateral incisor with

Hand Reamers and expanders in conjunction with synthetic bone and platelet-rich fibrin (PRF) (Fig 17-7e). Two weeks later, a 4.5 × 6.0–mm implant with a 2.5-mm well diameter was placed in the site of her right lateral incisor in conjunction with autogenous bone and PRF (Fig 17-7f). Postoperative healing was uneventful on the right side; however, on the left side, a discreet fistulation persisted without any secretion or suppuration. After 5 months of healing, the implants were uncovered. The right implant was restored with a porcelain-fused-to-metal (PFM) crown, but unfortunately the left implant was mobile and was removed, and the wound was closed with a combination of synthetic collagen, hydroxyapatite, and PRF (Figs 17-7g to 17-7i). After Fig 17-7 (a) Pretreatment CBCT reveals defects between the anterior maxilla, palatal, and alveolar maxillary processes. (b) Facial view of the exceptional lip contour and minimal scarring. (c) Nine-day postoperative clinical view of bilateral soft tissue mucogingival transposition flaps used to cover the transplant areas. (d) Nine-day postoperative palatal view. (e) Postoperative radiograph of implant on left side. (f) Postoperative radiograph of implant on right side. (g) Definitive crown on right side and new interdental papillae formation from new internal bone growth facilitated by the sloping shoulder of the implant with its double platform-switching design with a sealed IAI. (h) Radiograph of implant on right side showing new woven bone formation 3 months after crown placement. (i) Clinical view of postexplanted bed on left side; the nasal lining defect is deep inside. (j) Clinical view of left side after immediate reaugmentation with sandwich plasty technique. (k) Radiograph of new implant and augmentation. (l and m) Clinical and radiographic views of right lateral incisor implant and restoration after 9 months of being in function. Note the density of bone and improvement of interdental papillae.

5 months of healing, another implant was placed in the left lateral incisor site and restored uneventfully with a definitive PFM crown (Figs 17-7j and 17-7k). The right side also showed uneventful healing (Figs 17-7l and 17-7m).

Mandibular Squamous Cell Carcinoma

Surgical and prosthetic treatments for patients with oral cancer are important and complicated issues in dentistry.[27] These patients suffer from functional and aesthetic conditions that affect their eating and speech and often contribute to communicative, social, and psychologic dysfunction.[28,29]

The defects that follow surgical resection are unique to each patient and demand an individualized restorative plan to provide for his or her functional and anatomical needs.[30,31] The use of short Bicon implants to support a fixed TRINIA prosthesis provides the restorative flexibility necessary to offer such patients a meaningful and practical solution for their postsurgical reconstruction.[32–34]

A variety of head and neck tumors manifest in the jaw, their range extending from rare benign odontomas to semimalignant tumors such as keratocystic odontogenic tumors or ameloblastomas. The most frequently occurring malignant tumor is the squamous cell carcinoma, which requires a combination of therapies—each with serious side effects. Therapy for the treatment of squamous cell carcinoma often includes tumor resection, lymphadenectomy of the neck, radiotherapy, chemotherapy, reconstruction with microvascular reanastomosed soft tissue and bone grafts, and rehabilitation with implants and a fixed or removable telescopic full-arch prosthesis.

A large number of oral squamous cell carcinomas (OSCCs) have an etiology related to heavy use of nicotine and alcohol. Bosetti et al[35] demonstrated that cessation of smoking reduces the cumulative risk of upper aerodigestive cancers by half, even at the age of 50 years, when compared with lifetime smokers at the age of 75 years.

Two main concepts of multimodal tumor therapy can be distinguished by the sequence of radiochemotherapy and surgery to understand the therapeutic steps and thereby the complexity of implant rehabilitation in patients with tumors. Adjuvant therapy refers to therapy initiated in association with tumor resection followed by radiochemotherapy, whereas neoadjuvant therapy refers to treatment initiated with radiochemotherapy followed by tumor resection. After surgical removal of the OSCC, the defect is frequently reconstructed with a microvascular reanastomosed flap. The main difference between the two treatments is that neoadjuvant therapy irradiates the tumor and leaves a nonirradiated flap, whereas adjuvant therapy first removes the tumor and then irradiates the peritumorous tissues and the flap.

It is notable that a graft transferred to an irradiated transplant bed is far more complex and prone to complications and failures. A direct comparison of both treatments showed better cumulative survival rates (CSRs) especially in patients with metastatic lymphatic spread.[36] When tumors have invaded neighboring tissues (TNM stage T4N2), the 5-year survival rates with neoadjuvant therapy are significantly better (37.3% vs 9.7%). Depending on the resection defect, a graft composed of different tissues may be required. Bone defects may be reconstructed with a limited number of grafts. The most common grafts are the free jejunal, osteomyocutaneous fibula, the iliac crest, and the scapula transplant.[37] Fig 17-8 (a) Oral squamous cell carcinoma spreading from the mandibular left canine to the right second molar region. —_

The principle challenges of implant rehabilitations for patients who were treated for a tumor include:

• The potential risk of osteoradionecrosis after irradiation

• The limited number of microvascular bone transplants compatible with the size and shape of atrophic jaws and mouth opening

• The confirmed, inveterate smoker

In a systematic review, Nooh[38] investigated the timing of implantation and radiotherapy in adjuvant therapy. Preimplantation radiations showed smaller overall implant survival rates (88.9%) when compared with postimplantation radiations (92.2%), which suggests that the early osseointegration process is more disturbed by radiation than is later osseointegration. In the conventional preimplantation radiation group, the overall survival rates of implants depended on the location—78.9% in the maxilla compared with 93.3% in the mandible—and in either location, implants placed in free vascularized bone grafts versus nonvascularized bone grafts had a higher survival rate (89.3% versus 81.7%). Parbo et al[39] focused on fibula-reconstructed mandibles and reported an implant survival rate of 96%. In another study, the 5- and 10year CSRs were reported to be 97% and 79.9%, respectively.[40] Compared with nonirradiated healthy individuals, patients with a history of radiation and chemotherapy for tumors are expected to have a slightly higher implant failure rate.

Treatment 8

The following treatment involves a 70-year-old woman who quit smoking at age 40 years. She initially presented with a white lesion in her mandibular left alveolar area, which was confirmed histologically to be a fibrotic metaplasia with no sign of dysplasia. However, 4 years later, she presented with an ulcerating reddish lesion in the same area (Fig 17-8a). The biopsy confirmed an invasive squamous cell carcinoma. The patient received neoadjuvant radiochemotherapy comprising Mitomycin C (15 mg/m[2] , bolus on the first day), 5-Fluorouracil (750 mg/m[2] from day 1 to 5), and irradiation (25 sessions of 2 Gy each, a total dosage of 50 Gy) over a time span of 6 weeks. After a recovery period of 12 weeks, the tumor was resected with a selective neck dissection on the left side, the surrounding tissue was reconstructed with a microvascular reanastomosed jejunal flap, and the mandible was stabilized with a resection osteosynthesis plate (Figs 17-8b to 17-8d). Fig 17-8 (cont) (b) Panoramic radiograph after extensive resection of the mandible from the left angle to the right premolar region and stabilizing the mandible by means of osteosynthesis plate and screws. (c) Intraoral postoperative view of the microvascular reanastomosed jejunal free flap, which was transplanted to cover the huge mucosa defect after tumor resection. (d) Frontal clinical view after secondary reconstruction with microvascular reanastomosed fibula free flap partially osteotomized to be precisely pressed under the osteosynthesis plate in between the mandibular stumps. (Reprinted with permission from Ewers and Lambrecht.[33] ) (e) Panoramic radiograph 3 years after primary reconstruction with jejunal graft and 6 months after secondary reconstruction with fibular transplant. (Reprinted with permission from Ewers and Lambrecht.[33] ) (f and g) Frontal and lateral views 3 years after primary reconstruction with jejunal graft and fibular transplant. (h) Preparation of implant osteotomy. (i) Final osteotomy for a 4.0 × 5.0–mm implant. (j) Placing a 4.0 × 5.0–mm implant. (k) Seated implant with black polyethylene Healing Plug. (l) Harvested bone placed over the shoulders of the four 4.0 × 5.0–mm implants. (m) Postoperative radiograph of four 4.0 × 5.0 mm implants. —— ,

Because she showed no signs of tumor recurrence after 3 years, the bone defect was reconstructed with a microvascular reanastomosed fibula transplant (Figs 17-8e to 17-8g). One year later, the patient received four 4.0 × 5.0–mm Bicon implants (Figs 17-8h to 17-8m). After 4 months, the implants were uncovered, and a full-arch implant-level transfer impression was made (Figs 17-8n and 17-8o). At the next clinical visit, the implants were restored with a metal-free TRINIA prosthesis on four Fixed-Detachable Abutments (Figs 17-8p and 17-8q). The clinical and radiographic images revealed satisfactory function and aesthetics, as well as an excellent reconstruction of the large soft and hard tissue defects (Figs 17-8r to 17-8t). The middle abutment originally irritated the patient’s lip, so the abutment was removed, and the bore of the prosthesis was filled with a composite resin (Figs 17-8u to 17-8aa). The irritation was caused by the wide, nonanatomical curve in the fibula transplant that resulted in the implant having a labial position. The prosthesis has now functioned on three implants for 5 years.

Fortunately, 6 years after the loading of the implants, and 10.5 years after the tumor resection, the CT scan revealed neither the presence of tumor recurrence nor evidence of lymphatic spread. Comparison of the radiograph taken shortly after loading (see Fig 17-8t) and that taken at the 5.5-year recall (Fig 17-8bb) reveals an increase in the crestal bone, which is consistent with Wolff’s law and the threshold theory of Frost. This is noteworthy because the bone is a microvascular reanastomosed fibula.[41–43] Fig 17-8 (cont) (n) Four blue 2.5-mm Impression Posts and Sleeves inserted in wells of implants for making of an implant-level transfer impression. (o) View of four white polyetheretherketone (PEEK) Healing Abutments seated in the implant wells after suturing. (p) Occlusal view of screw-retained TRINIA bar on a soft tissue model. (q) Occlusal view of TRINIA prosthesis. (r) Intraoral view of screw-retained TRINIA prosthesis. (s) Screwretained TRINIA prosthesis in occlusion with natural teeth. (t) Radiograph of fastened TRINIA prosthesis. (Reprinted with permission from Ewers and Lambrecht.[33] ) (u and v) Frontal and lateral views of the TRINIA prosthesis. (w) Intraoral view after replacement of one Fixed-Detachable Abutment with a provisional abutment because of irritation to the lip as a result of the fibular graft being contoured too facially. (x) Modified TRINIA prosthesis after replacement of one Fixed-Detachable Abutment. (y) Radiograph after replacement of one Fixed-Detachable Abutment. (z and aa) Frontal and lateral views of mandibular prosthesis in occlusion 4 years after primary loading and 9 years after tumor resection. (bb) Radiograph 6 years after primary loading and 10.5 years after tumor resection. Fig 17-9 (a) Facial scarring 7 years after oncologic surgery. (b) Intraoral skin graft. (c) Preoperative radiograph. (d) Three 4.0 × 5.0–mm implants placed with their untrimmed black polyethylene Healing Plugs. (e) Harvested bone covering the shoulders of three implants. (f) Radiograph 5 months after implant placement. (g) Three blue 2.5-mm guide pins in wells of implants. (h) Three titanium provisional abutments at the time of uncovering. (i) Periotest confirming integration of the implants.

Treatment 9

Another treatment of a mandibular squamous cell carcinoma for a 68-year-old woman included the resection of her lower lip, buccal mucosa, alveolar gingiva, and floor of the mouth and a partial resection of her mandible. To cover the residual defect in her mucosa, a skin nasolabial flap was tunneled transbuccally to the area of the defect in the oral cavity. A postoperative remote gamma therapy of 36 Gy was administered.

One year later, bilateral metastases were detected in the lymph nodes of her neck. Following the bilateral removal of the neck lymph nodes, polychemotherapeutics were administered.

Because she had been asymptomatic for 7 years after her last surgery, it was tentatively decided to place three short Bicon implants in the areas of the mandibular right lateral incisor, left lateral incisor, and left second premolar for the support of a fixed TRINIA prosthesis. The soft tissue in the area where the implants were to be placed included the previously grafted 6.0 × 3.0–cm skin flap, which extended from the proximal region of the floor of the mouth and inner surface of the left lower lip to the vestibule of the resected alveolus between the area of the right lateral incisor and left first molar. Additionally, there was postsurgical scarring on the midline of her chin and lower lip (Figs 17-9a and 17-9b). Radiographic analysis confirmed that there were no pathologic changes in the bone (Fig 17-9c).

The implants were placed using local anesthesia and conscious sedation. The incision was carried out along the alveolar crest in the area where the reconstructive surgery and skin graft had been performed. After raising a skin-periosteal flap, three short 4.0 × 5.0–mm Bicon implants were placed (Figs 17-9d and 17-9e). The postoperative course was uneventful. A 5-month postoperative radiograph showed normal healing (Fig 17-9f). The implants were uncovered using local anesthesia, the Healing Plugs were removed, and guide pins and Sulcus Formers were used to create appropriate sulci for the seating of the Healing Abutments (Figs 17-9g and 17-9h). All of the implants were clinically stable and appeared to be osseointegrated. When tested with a Periotest (DentiSystem) instrument, the test data were –4.8, –4.9, and –4.7, respectively (Fig 17-9i). After 2 weeks, the Healing Abutments were removed, and a full-arch implant-level transfer impression and occlusal bite registration were made using Impression Posts seated in the implant wells with their corresponding acrylic sleeves (Figs 17-9j and 17-9k).

A nonremovable provisional acrylic prosthesis was used during the first 8 months following implant uncovering. To satisfy the patient’s aesthetic needs, the maxillary teeth were restored based upon the appearance of her teeth in photographs taken 50 years earlier. Subsequently, a fixed TRINIA prosthesis was fabricated using CAD/CAM technology (Figs 17-9l to 17-9n). A postoperative evaluation was performed consistently every 3 months, revealing healthy soft tissue under the prosthesis. Fig 17-9 (cont) (j) Three blue 2.5-mm Impression Posts and Sleeves prior to the making of an implant-level transfer impression. (k) Facebow recording the occlusal relationships. (l) Virtual image of scanned abutments. (m) Milled TRINIA framework on a soft tissue model. (n) Finished TRINIA prosthesis with three abutments. (o and p) Two-year postoperative clinical image and radiograph of finished TRINIA prosthesis.

Fortunately for the patient, her normal chewing and speech were restored, and she was quite satisfied with the aesthetic result, as can be seen in the 2-year follow-up images (Figs 17-9o and 17-9p). In light of the significant improvement of her speaking and chewing, the remaining scarring of her chin and lip faded from her focus. After 2 years of loading, the level of bone around the implants remained unchanged. The successful dental rehabilitation of this cancer patient was clearly facilitated by the use of short Bicon implants and the innovative material TRINIA.

Irradiated Bone

Approximately 60% to 80% of tumor patients will undergo radiotherapy before or after surgery.[44] After the primary threat to their life has receded, the patients’ concerns shift to restoring their quality of life to the extent possible. In issues involving the mouth, the use of dental implants has become one of the most important restorative modalities for providing patients with a good functional and aesthetic recovery.[45,46] However, radiotherapy frequently leads to complications in providing implant therapy. The tissue in the irradiated area is subjected to hypoxia, a decrease in vascularity, and ultimately a reduction of cells.[47,48] Among the cells destroyed are the osteoblasts, whose destruction leads directly to impaired bone modeling and remodeling and in some instances will cause osteoradionecrosis (ORN).[49,50] Although these factors may lead to an increase in the frequency of implant failure, there are adjunctive therapies, such as hyperbaric oxygen, osteogenic growth peptides, and bone morphogenetic protein, which can be used to improve the success rate. However, the availability and cost of such therapies often make them impractical.[51] Fig 17-10 (a) Radiograph of a 70-year-old man with extensive ORN of his right mandible after 72-Gy radiation therapy. (b) Radiograph after extraction of all of the patient’s remaining teeth. (c) Intraoral view after split-thickness flap and initiating a half-moon-shaped periosteal flap for the right lateral implant osteotomy. (d) View of half-moon-shaped periosteal flap. (e) View of seated 4.0 × 5.0–mm Bicon implant. Forceps hold the lifted half-moon periosteal flap. —_

In many publications, there is considerable variation in the reported rates of implant success; for example, success rates in patients who had received radiotherapy ranged from 70% to 99%.[52–55] A recently published systematic literature review showed that in preimplantation radiation therapy, the implant survival rate was significantly higher for the mandible (93.3%) than for the maxilla (78.9%), and for procedures involving grafted bone, it was 87.5%. Similarly, the implant survival rate was higher when implants were placed in free vascularized grafts (89.3%) than in nonvascularized bone grafts (81.7%). It was also noted that a radiation dose above 55 Gy significantly decreased implant survival.[38]

Additionally, reports show that the accumulation of a supra- and subgingival bacterial biofilm is one of the consistent risk factors for peri-implantitis. If they are to avoid this potential source of infection, it is particularly important that these patients control their supragingival biofilm.[56] On the other hand, patients cannot control subgingival bacteria that potentially contribute to peri-implantitis; this is especially true if there are microgaps and micromovement in the IAI. The Bicon IAI is a bacterially sealed locking-taper cold weld with neither microgaps nor micromovement. Therefore, it is logical and prudent to use Bicon implants in patients with irradiated mandibles and maxillae (see chapter 6 for a detailed description of the bacterial seal).[57] The treatments of three patients with very different medical histories follow.

Treatment 10

The first patient was a 70-year-old man who suffered from cancer on the right side of his tongue and the floor of his mouth. He was irradiated with 72 Gy. Subsequently, because of the overall poor condition of his dentition, all of his remaining teeth were removed (Figs 17-10a and 17-10b). In the month following, some of the extraction sites became osteoradionecrotic. There appeared to be danger of a spontaneous fracture of the mandible because of a large, necrotic bone defect on the right side (see Fig 17-10a). His medical condition was poor, and any attempt to remove the necrotic bone or to try to stabilize the mandible with an osteosynthesis plate under general anesthesia was contraindicated. The patient knew he had only a few months to live; however, he did not want to spend these months unable to eat his favorite foods.

There was a reluctance to expose the patient to any source of infection in his desperate condition; the possibility of subgingival bacterial leakage at an IAI could contribute to peri-implantitis and constitute a serious threat in this situation. However, there was no concern about leakage from the bacterially sealed IAI of the Bicon system; therefore, a decision was made to proceed with implant therapy.

Two months after the extractions (see Fig 17-10b), four 4.0 × 5.0–mm implants were placed in the mandible. Because of the difficult situation and the compromised hard and soft tissues, a very mild local anesthetic was used. The operative site was opened with an epiperiosteal and a split-thickness flap and then with a conservative half-moon incision to raise the smallest feasible area of the periosteum over the proposed implant sites (Figs 17-10c to 17-10e). Fig 17-10 (cont) (f) Four red 2.0-mm guide pins indicating the trajectory of the four implants. (g) Four seated 4.0 × 5.0–mm Bicon implants with cut polyethylene Healing Plugs. (h) Harvested bone placed over the shoulders of the four implants. (i) Suturing with 5.0 resorbable sutures to readapt the periosteal flap. (j) Sutured mucosa with single-knotted 5.0 resorbable sutures. (k) Postoperative radiograph of four implants with close proximity of the right implant to the necrotic bone. (l) Healed mucosa 10 days after placement of the implants. (m) Four blue 2.5-mm titanium impression posts in place for the making of a full-arch implant-level impression. (n) Initial bite registration with waxed mandibular teeth arrangement. (o) View of both mandibular and maxillary waxed teeth arrangements. (p) View of four Fixed-Detachable Abutments in a stone model. (q) Occlusal view of screw-retained TRINIA full-arch prosthesis. (r) Intraoral view of screw-retained TRINIA full-arch prosthesis. (s) Facial image of TRINIA prosthesis in occlusion. (t) Radiograph of screw-retained TRINIA prosthesis.

The implants were covered with bone harvested from their osteotomies (Figs 17-10f to 17-10h), the periosteum was sutured back in place with 5.0 resorbable sutures (Fig 17-10i), and the mucosa was closed using a single-knotted 5.0 resorbable suture (Fig 17-10j). The postoperative radiograph showed that the posterior right implant was very close to the necrotic bone (Fig 17-10k); however, the wound over the implants healed uneventfully (Fig 17-10l). After 3 months, the implants were uncovered, and a full-arch implant-level transfer impression and bite registration were made (Fig 17-10m). Ten days later, a preliminary prosthesis was evaluated, and a second occlusal registration was made (Fig 17-10n).

Because of difficulties with the occlusion, a second preliminary evaluation had to be made, as well as a new TRINIA prosthesis and another bite registration (Figs 17-10o and 17-10p). Ten days later, the new prosthesis was placed (Figs 17-10q to 17-10s). The mandibular and maxillary prostheses fit very well despite the challenging occlusal situation. The postoperative panoramic radiograph reveals how difficult it was to adapt the oblique occlusal plane into a well-functioning occlusion (Fig 17-10t). The patient lived a little more than 1 year, and he enjoyed the pleasure of eating without peri-implant issues despite his compromised hard and soft tissues. Fig 17-11 (a) Osteocutaneous fibula vascularized free flap with four 4.0 × 6.0–mm Bicon implants. (b) Three-week postoperative panoramic radiograph. (c) Fourteen-month postoperative site before reduction of the skin flap with Z-plasties. Note the mucosal perforation, which occurred 2 months after initial surgery. (d) Twenty-month postoperative panoramic radiograph revealing four osseointegrated implants and complete healing of lower border fibula sequestration. The reconstructive plate was removed after 8 months. Note the better healing of the screw holes in the transplanted bone than in the patient’s mandible. (e) Surgical site 1 month after flap reduction with Z-plasties and 15 months after initial surgery. —— ,

Treatment 11

The second patient, a 40-year-old man who smoked two packs of cigarettes a day and consumed beer and distillates on weekends, presented with an ulcerating lesion in the anterior floor of his mouth. The lesion was approximately 4 cm in size, and its center was slightly to the right of the midline. It was irregularly shaped and superficial upon palpation. The ventral border of the lesion extended to the attached gingiva, and the dorsal margin extended about 1 cm approaching the hypoglottis. The CT scan showed no radiographic evidence of intrabony invasion. The preoperative and definitive histologic examination revealed squamous cell carcinoma; the invasive pattern of spread was Gr. I, staged pT2, pN0, pMx.

The primary treatment consisted of complete resection of the base of the mouth, including the mandible, the ventral third of the tongue, and both sublingual glands. Neck nodes were removed in the extension of the supraclavicular functional on the right side and supraomohyoid functional on the left side. The total number of microscopically inspected nodes was 108, and all were negative. Immediate reconstruction of the defect by means of a complex microvascular osteocutaneous fibula free flap was performed without any early postoperative complications.

Three 4.0 × 6.0–mm implants, each with a 2.5-mm well, were placed into the osteocutaneous fibula vascularized free flap, and one was placed in the residual mandible during the initial surgery (Figs 17-11a and 17-11b). The patient refused the postoperative multimodal part of the recommended therapy. Two months after being placed during the transplant surgery, the black Healing Plug of the implant placed in the mandibular bone perforated its mucoperiosteal cover without complication (Fig 17-11c). Eight months after the surgical monotherapy, the reconstructive mandibular plate was removed for a minor intraoral bone sequestra that did not affect the implants (Fig 17-11d). Fortunately, histologic examination of the sequestered tissue proved to be a nonspecific granulation tissue.

A year after the initiation of his treatment, two enlarged lymph nodes were detected in the caudal area of the region V cervical lymph nodes. Part of the postoperative scar and 17 lymph nodes were removed and found to be histologically negative for metastasis. Fourteen months after the primary surgery, the soft tissue part of the flap was reduced in volume by multiple Z-plasties, the skin surface of the neomandible was removed, and several free palatal mucosal transplants were applied; their healing was uneventful (Fig 17-11e). Sixteen months after surgery, three superficial enlarged nodes on the right side (region Va) were discovered and removed. Two nodes that were in close proximity contained metastases without extranodal spread. Radiotherapy was initiated a month later, including the primary site until 20 Gy of treatment, after which time the primary site was excluded. Twenty months after their placement, the four implants were uncovered, their Healing Plugs were removed, and an implant-level transfer impression was made, after which the white Healing Abutments were placed (Figs 17-11f and 17-11g). Subsequently, a master stone model was poured with four implant analogs into which guide pins were inserted, indicating their divergent trajectories (Fig 17-11h). The patient’s lip line, midline, and smile line were also recorded with a wax rim (Fig 17-11i). Universal Abutments were then selected to have 1 to 3 degrees of divergence among them. Fig 17-11 (cont) (f) Four blue 2.5-mm acrylic sleeves and Impression Posts for the making of an implant-level transfer impression. (g) Four PEEK Healing Abutments. (h) Master model with four guide pins revealing the divergent trajectories of the four implants. (i) Initial recording of the relative position of the patient’s jaws. (j) A lightcured resin verification and seating jigs were fabricated to verify the retentiveness and path of insertion of the proposed prosthesis as well as to facilitate the orientation and initial seating of the four Universal Abutments. (k) Milled bar nested in pink TRINIA disc. (l) Seating jig facilitating the placement of the third Universal Abutment. (m) Placement of a milled coping that was shortened to provide clearance because of the patient’s minimal interocclusal space. (n) Intaglio view of the finished TRINIA telescopic restoration with four milled copings that were intraorally cemented with resin cement into the TRINIA prosthesis. Flowable composite was used to fill any voids. (o) Facial view of the seated TRINIA telescopic restoration. (p) Postoperative panoramic radiograph. (q) Patient’s smile.

Once the abutments were selected, the efficacy of the prosthesis’s path of insertion, as well as the retentiveness of the proposed restoration, was verified with the fabrication of a light-cured resin jig with four milled copings. A lightcured resin orientation jig was also fabricated to facilitate the seating of the four abutments intraorally (Fig 17-11j). After employing the appropriate designing procedure, a prosthetic substructure was milled from a disc of pink TRIN-

IA material (Fig 17-11k). The seating jig was used to intraorally place the selected abutments into the wells of the implants (Fig 17-11l). The modified milled copings were placed onto the seated abutments with petroleum jelly to facilitate their removal once they were cemented into the bores of the TRINIA prosthesis (Figs 17-11m and 17-11n). The finished prosthesis provided a meaningful improvement in the patient’s quality of life (Figs 17-11o to 17-11q). Fig 17-12 (a) Radiograph of a 67-year-old man’s mandibular teeth and two CAMLOG implants before radiation therapy. (b) Radiograph after radiation therapy and removal of the patient’s implants and teeth. (c) Radiograph after placement of six 4.0 × 5.0–mm implants and one 4.5 × 6.0–mm implant. (d) View of TRINIA prosthesis with six seated abutments. (e) Radiograph of cemented TRINIA prosthesis; note the bony defect where the posterior CAMLOG implant used to be. (f) Intraoral image of full-arch TRINIA prosthesis at 1-year recall. (g) Panoramic radiograph at 3-year recall.

Treatment 12

The third patient, a 67-year-old man, suffered from a maxillary right sinus carcinoma and was irradiated with a postoperative dose of 65 Gy. Eighteen months after treatment, he started to experience bone loss around the two implants on the right side of the mandible, eventually losing the two implants and several teeth (Figs 17-12a and 17-12b). Six months later, and 2 years after his radiotherapy, six 4.0 × 5.0–mm Bicon implants and one 4.5 × 6.0–mm Bicon implant were placed (Fig 1712c). For better provisional prosthetic retention, the mandibular right canine and left second molar were not extracted until the day that the full-arch prosthesis was placed.

After 3 months of healing, the implants were uncovered. The implant in the site of the right second molar failed to integrate and was removed. This was the same site where a previous implant had failed. During the same patient visit, a full-arch implant-level transfer impression was made, and an occlusal registration was taken. Three weeks later,

the definitive TRINIA full-arch prosthesis was placed (Figs 17-12d to 17-12f).

Unfortunately, the wound at the site of the lost implant failed to heal and resisted all attempts at closure, including a mucoperiosteal pedicle flap from the buccal. Eight months later, another surgical intervention was performed. Upon opening the wound, a surprisingly large bone defect was seen at the site where two previous implants had failed to integrate. An extensive bone curettage and necrosectomy was performed, and the wound was closed with a mucoperiosteal pedicle flap. A postoperative radiograph revealed extensive bone reduction in the area of the mandibular right first and second molars.

Primary wound healing was uneventful without a mucosal dehiscence. One year later, a residual bone defect was still evident, but the appearance of the hard and soft tissues and the radiographic result were very satisfying. The 3-year recall panoramic radiograph showed an unchanged successful result without any bone loss (Fig 17-12g).

Conclusion

The treatments presented in this chapter provide ample evidence of the remarkable clinical capabilities and benefits provided by the Bicon system for clinicians and their deserving patients. Additionally, the collective documented experiences of many clinicians worldwide have provided insights not only for using the unmatched clinical capabilities of the Bicon protocols for treatment of their patients, but also for the development of new therapies.

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18

Bone Voids

Mauro Marincola | Laura Murcko | Miguel Simancas-Pallares | Pieter Boshoff | José Luis Alonso Padilla

In 1915, one of the founders of modern dentistry in the United States, G. V. Black, observed lesions that he described as chronic osteitis of intramedullary cavities, created by a gradual but continuous process of cellular death. The “cavities” were up to 5 cm in size, and he wondered about their unique ability to produce extensive bone destruction without causing pain, pus, redness of the gingiva, swelling of the jaw, or an increase in the patient’s body temperature.[1–3 ]

Bone pathologies that share similar features to Black’s intramedullary cavities continue to be observed and have been assigned a variety of names over time, including traumatic bone cysts , solitary bone cysts , hemorrhagic cysts , simple bone cysts , pseudocysts , osteoporotic bone , and marrow defects .[4] Although there is little agreement as to their name, there is consensus regarding the radiographic, histologic, and clinical appearance of the lesions.[5] For the sake of simplicity, these cystlike lesions are referred to as bone voids or lesions for the remainder of this chapter.

Some studies suggest that the etiology of these lesions can be found in traumatic events (eg, a difficult extraction, failed endodontic therapy, or failure of a tooth bud to develop properly).[6] There have also been multiple observations that the lesions seem to occur more often in the posterior mandible of middle-aged women. Additionally, there are speculations regarding far-reaching systemic effects, though there are insufficient data to support these assertions.[7]

Bone voids are not among the more common jaw pathologies encountered by implant clinicians, but failure to recognize and treat them can result in implant displacement followed by partial or complete mandibular paresthesia, or failure of osseointegration.[8–13]

The purpose of this chapter is to heighten clinicians’ awareness of the diagnostic difficulties and surgical risks associated with bone voids (Fig 18-1). The discussion includes recognition of the subtle telltale signs of a bone void and how to

Fig 18-2 (a) Panoramic radiograph of a 2- to 3-mm-thick crest outlining a large radiolucent area in the edentulous first molar site. (b) Panoramic radiograph of edentulous spaces filled with synthetic graft material. Fig 18-1 Radiograph showing implant that passed through an osteotomy into a bone void. proceed when faced with one. Additionally, the relevance and importance of an implant’s design is discussed, as well as the part it plays in the management of the implant’s outcome when a clinician’s instrument or implant drops into an undetected hole in the alveolar bone. The chapter concludes with three examples of how clinicians have managed unexpected encounters with bone voids during surgery.

Finally, though there is mention in this chapter regarding the etiology and nomenclature of these lesions, there is no intention to engage in any discussion concerning what some consider a controversial diagnostic entity; the sole objective is to share many decades of clinical implant experience and knowledge about the existence and management of voids in the alveolar bone for the benefit of clinicians and their patients.[14]

Radiographic Recognition of a Bone Void

In implant dentistry, alveolar bone quality is usually defined by one of four distinct categories: type I to IV (see chapter 8). For the purposes of this discussion, a bone void is similar to type IV bone; however, it is further characterized as having a dense cortical exterior, encasing a center bereft of cancellous bone. Although panoramic and periapical radiographic images, as well as computed tomography (CT) and cone beam CT (CBCT) files, are adequate for evaluating the size and volume of bone in an edentulous space, these technologies are not always sufficiently reliable to assess the density and quality of bone. Bender and Seltzer,[15] in their roentgenographic study of experimental lesions in bone, concluded that lesions in cancellous bone could not be detected roentgenographically unless the inner surface of the cortex had been perforated or eroded.

Although it takes an experienced clinician to consistently evaluate and recognize the radiographic appearance of a bone void, every clinician can begin to recognize it with practice. The telltale radiographic appearance of a bone void comprises a thick, radiopaque cortical layer encasing and masking an ill-defined radiolucent area of diminished or missing cancellous bone. The amount of synthetic graft material placed in a void may give one an appreciation for the size of the bone void (Fig 18-2). CBCT imaging will sometimes reveal the presence of a void by displaying the complete absence of trabecular bone as an extended radiolucent area surrounded by a 2- to 3-mm-thick radiopaque cortical layer (Fig 18-3). Admittedly, these lesions are difficult to detect, but there is benefit simply in knowing that these lesions exist and in using an implant protocol that gives the clinician visibility of the operative site at every stage of the procedure. Fig 18-3 (a and b) CBCT scans of a bone void.

Histology of the Bone Void

From a histologic point of view, bone voids—unlike cysts— have no epithelial lining and may appear as either an empty space or filled with discolored fluid and cellular debris. Histologic examination of material removed from mandibular a 278

bone voids in eight patients revealed contents that included inflammatory cells, adipocyte cells, and dystrophic fragments of bone surrounded by hemorrhagic debris, but there was no evidence of an epithelial lining or cystic residue (Fig 18-4).

The Role of Implant Design in Recognizing the Bone Void

The Bicon implant has a unique design and placement protocol that minimizes a number of the placement challenges associated with threaded implants; this is particularly evident when dealing with the unexpected, such as a void in the bone. For example, the Bicon surgical placement technique differs from those of threaded systems in that the osteotomy for a Bicon implant is prepared with low-speed drilling without irrigation, and its sloping shoulder does not rely on achieving primary stability from the cortical rim of the osteotomy. The implication of these features is that the clinician can see what is happening at every stage of the placement process. The placement protocol directs the clinician to assess the quality of the bone being harvested and to use an instrument such as a spoon curette to inspect the integrity of the floor and walls of the final osteotomy before the implant is placed; therefore, if bone pathology is present, it can be detected and managed.

When confronted with the precarious conditions of a large void in the bone, a clinician must be aware that displacement of the implant is a real possibility, even with grafting. If a decision is made to proceed with the implant placement, it is prudent to use a Sinus Lift Abutment (as is shown in one of the following example treatments [see Fig 18-13h]), which minimizes the risk of losing the implant within the void. However, a clinician’s clinical judgment may also dictate postponement of the implant placement until a future time.

It is also worth noting that if the cortex is sufficiently thick to provide primary stability, it is possible that an unwitting clinician using a threaded implant may not recognize the presence of the bone lesion and, in placing the implant, may suspend it over a bone void filled with toxic debris. Conversely, the Bicon system provides clinicians with the opportunity to recognize and treat a pathologic condition and the possibility of continuing with the planned treatment.

Management of the Bone Void

Although the Bicon implant’s design and surgical techniques provide clinicians an opportunity to recognize the presence of a bone void before placing an implant, successful management of the event depends upon the skill and prudence of the clinician. Low-density bone, which is not often seen preoperatively, is the most common compli-

Fig 18-4 Histologic image of the material from the bone defect revealing the necrotic nature of the trabecular bone.

cation experienced by implant clinicians.[16] The bone void is a similar, though greater, challenge than low-density bone because there is a total absence of cancellous bone and an abundance of undesirable material.

That being said, there are certain observations that the clinician can make that indicate the presence of a bone void. Depending on the experience of the clinician, the first sign of a bone void could be found in the preparation of the pilot osteotomy, which may seem to take longer because of the presence of thick, dense, and resistant cortical bone. Once the cortical bone is perforated, the clinician perceives a sudden drop, as if into a hole. The osteotomy will start to bleed heavily, and fatty droplets may be visible on the surface of the blood. While drilling with the Latch Reamers, the patient may feel pain even though the osteotomy is away from the mandibular nerve and the normal signs and symptoms of adequate anesthesia are present. Some suggest that the pain is most likely related to nerves originating from the damaged nerve of a previously extracted tooth.[17,18] If the clinician still has not realized the situation when no harvested bone is collected in the flutes of the Latch Reamers, then confirming the interior of the osteotomy will provide clarity when the clinician discovers that the floor of one or more of the osteotomy walls is missing.

These lesions contain necrotic and osteoporotic bone and require surgical procedures to prepare the site for healing or continuing with implant placement. Treatment with antibiotics or other therapies will not restore the bone to a healthy state—in fact, only vigorous curettage, irrigation, and possibly the addition of guided bone regeneration can induce healing within the site. Whether or not grafting is done, the prerequisite for bone healing and regeneration is the thorough removal of the necrotic lesion. If this is not performed, the surgical site will remain compromised with an increased risk of implant failure.[19,20]

The material extracted from a bone cavity is a semiliquid, gelatinous type of marrow material mixed with bone residue, which is easily distinguished from healthy spongy

Fig 18-7 Radiograph of implants placed at the time of grafting. Walls of each osteotomy are intact.

Fig 18-5 Gelatinous tissue is removed with a curette.

Fig 18-6 Radiograph of a paralleling pin in the bone void revealing its shape, often as an intact lingual wall with the bone defect extending in up to three directions: mesial, distal, and buccal.

Fig 18-8 Two osteotomies communicating with each other because of bone defects. Fig 18-9 Graft material extends in all directions, so implant placement will be postponed for 6 months.

Fig 18-10 (a and b) Grafting syringe is used to fill the void with SynthoGraft in all directions without compressing the material over the inferior alveolar canal.

bone (Fig 18-5). While engaged in the removal of the necrotic debris, the clinician needs to be alert and cognizant of the possibility that the inferior alveolar nerve may be suspended within the void or nearby. In some cases, the appropriate curettage of a bone defect can take up to 30 minutes because it is necessary to carefully debride the entire defect until a solid osseous surface is reached. Once the contents of the void have been thoroughly removed through vigorous curettage, the crypt is rinsed with a sterile solution of saline or water before the osteotomy is then inspected.

The shape of the voids may vary, but the defects typically extend distally toward the buccal and inferiorly toward the mandibular canal (Fig 18-6). The lingual wall is rarely involved. An implant may be inserted simultaneously with the grafting material as long as the implant plateaus are in contact with at least two intact walls of the osteotomy (Fig 18-7). For multiple implant placements, it is not uncommon for the osteotomies to be contiguous with one another (Fig 18-8). If a cavity extends in all directions, the implant placement should be postponed for 6 months after the site has been treated (Fig 18-9).

SynthoGraft, a pure-phase beta-tricalcium phosphate material, is an excellent graft material for any bone defect or void when mixed with the patient’s own blood. When using a grafting syringe, the SynthoGraft mixture should initially be directed toward the buccal aspect of the defect and then to the mesial or distal, without compressing the material apically toward a missing floor. Any pressure on the mandibular nerve could cause temporary or permanent nerve injury (Fig 18-10). Fig 18-11 (a) Preextraction radiograph of a primary tooth in a 19-year-old patient. (b) Postextraction radiograph. (c) Clinical view upon discovering a void after extraction of the distal root of the primary tooth. (d) Radiograph of a spoon excavator demonstrating the depth of the void, which extends the entire distance between the premolar and molar. Fig 18-12 (a) Panoramic radiograph revealing a radiolucent area mesial to the mandibular right second molar. (b) A raised full-thickness gingival flap revealing what appears to be a thick, dense layer of cortical bone. —>

Treatment 1

Treatment 2

Elements of the foregoing discussion are exemplified in the treatment of a 19-year-old woman whose primary mandibular left molar had recently become sensitive to touch; she wished to have the tooth extracted and replaced with an implant. After the initial evaluation of the radiographs, it appeared that her treatment would be straightforward, but the removal of the residual root of the primary molar revealed a tiny opening in the floor of the socket (Figs 18-11a to 18-11c). The tiny opening soon gave way to a gaping void beneath the otherwise dense cortical ridge, as shown in a radiograph of a spoon excavator deep in the body of the void (Fig 18-11d). The lesion was carefully and gently explored because its depth was unknown and the alveolar nerve was close. The void was completely debrided with spoon excavators until the hard bony walls of the defect could be felt. It was rinsed with a sterile saline solution, but the size of the void dictated the postponement of the implant placement for several months until the void had healed.

Another example of how to clinically manage bone void lesions is demonstrated in the case of a 52-year-old woman who presented with 19 missing teeth. The mandibular second premolars and first molars were missing, having been extracted many years earlier following an infection consequent to a failed root canal therapy. The treatment called for the placement of implants for each missing mandibular second premolar and first molar. A careful preoperative evaluation of a panoramic radiograph revealed a circular formation, 5 to 6 mm in diameter, located mesial to the mandibular right second molar (Fig 18-12a). A full-thickness gingival flap was raised, revealing what appeared to be a thick, dense layer of cortical bone—the kind often found overlying a bone void, though there was no external sign of an underlying defect (Fig 18-12b). Upon entering the molar site, the pilot drill dropped into a partial void. Using Latch Reamers, the osteotomies were widened in 0.5-mm increments. An osteotomy was prepared for 4.5- and 5.0-mmwide implants. After completion of the osteotomies, tactile inspection revealed that only their mesial and lingual walls were intact. The surgical site contained a large distal void measuring 10 mm in depth, and the osteotomy floor was also missing (Figs 18-12c and 18-12d). The buccal defect extended only a few millimeters. Fig 18-12 (cont) (c) The osteotomy in the molar region showing complete absence of the distal wall. The depth gauge penetrates 10 mm to the distal. (d) The osteotomy floor is missing. (e) The lesion being entirely debrided using sharp curettes and excavators. (f) Graft material, inserted toward the distal, partially fills the defect. (g) First implant placed at the same time as the grafting. (h) Healing Plugs in the wells of the two implants placed at the same time as the grafting. (i) Primary closure of the flap. (j) Postoperative radiograph of the two implants. Note the distal, buccal, and apical extensions of the graft. (k) Two-year postoperative radiograph of the prosthetic restoration.

The entire lesion was carefully debrided using sharp curettes and excavators (Fig 18-12e), and it was irrigated with a sterile saline solution. A mixture of SynthoGraft and the patient’s blood was inserted distally, partially filling the defect (Fig 18-12f). A 5.0 × 6.0–mm and a 4.5 × 6.0–mm implant were immediately placed because they would be in direct contact with the mesial and lingual walls of the osteotomy (Figs 18-12g and 18-12h). The surgical site was then sutured (Fig 18-12i). The postoperative radiograph revealed the size of the defect and the extent of the grafting (Fig 18-12j). A 2-year postoperative radiograph shows a stable result (Fig 18-12k). Fig 18-13 (a) A preoperative periapical radiograph reveals a large circumscribed lesion distal to the mandibular left premolar. (b and c) CT imaging also reveals the radiolucent area distal to the mandibular premolar. (d) Radiograph of a spoon excavator revealing the extent of the defect. (e) Clinical image of a spoon excavator passing between the two osteotomies. (f and g) SynthoGraft mixture is injected into the osteotomies. (h) Sinus Lift Abutment attached to an implant as its plateaus are mortised with SynthoGraft mixture, prior to being inserted into its osteotomy. (i) Implants with Sinus Lift Abutments and provisional abutments attached are seated into the wells of the osteotomies with SynthoGraft mixture. (j) SynthoGraft mixture is applied around the transitional abutments. (k) Postoperative radiograph with the graft material indicating the extent of the defect.

Treatment 3

A similar treatment was performed for a 70-year-old woman whose preoperative radiograph and CT revealed a radiolucent area distal to her mandibular left premolar (Figs 18-13a to 18-13d). A full-thickness flap was raised, and two osteotomies were prepared. The void was such that the osteotomies communicated with each other (Fig 18-13e). After carefully debriding and irrigating the bone crypt, a mixture of SynthoGraft and the patient’s blood was injected into the osteotomies (Figs 18-13f and 18-13g). Because of the size of the void, a provisional abutment was attached to one of the implants, while a Sinus Lift Abutment was attached to the other to minimize the possibility of displacement, and the implant plateaus were mortised with a SynthoGraft mixture (Fig 18-13h). The implants were then placed into the osteotomies (Figs 18-13i and 18-13j). The postoperative radiograph reveals the extent of the bone defect (Fig 18-13k). Fig 18-14 (a) Radiograph of a seemingly ideal implant placement. (b) Radiograph of the inadvertent migration of an implant into an undiagnosed bone void. (c) CBCT image of the implant in the unrecognized bone void.

Case 4

In this treatment, a Bicon implant was placed in the mandible without following the surgical protocol of checking the integrity of the four walls and floor of the osteotomy. After seemingly placing the implant ideally in its osteotomy, it inadvertently fell into a significant bone void when its Healing Plug was placed into the well of the implant (Fig 18-14).

Conclusion

Clinicians need to be aware of the possible surgical complications associated with bone voids, such as those described in this chapter and as evidenced by the postoperative radiographs shown in Fig 18-14, in which the implant migrated through an undetected defect in the wall or floor of its osteotomy. The clinical treatments that were presented demonstrate several ways in which bone defects can be successfully managed during the placement of implants, including the analysis of preoperative radiographs to search for the characteristic appearance of bone voids and an awareness of variations encountered in the preparation of the osteotomy—namely, difficulty in penetrating the cortical layer and a sense of falling into a space.

The Bicon implant’s design, with its sloping shoulder and surgical protocol, makes it not only possible but also imperative for a clinician to evaluate the integrity of the four walls and floor of an osteotomy prior to placing an implant. Such an evaluation is necessary because, unlike a threaded implant, a Bicon implant receives no retention or stability from the crestal or cortical rim of bone. Failure to properly evaluate the osteotomy in the presence of either poor bone quality or a bone void such as described in this chapter could result in displacement of the implant, loss of the implant within the void, or a failure to achieve osseointegration. On the other hand, because threaded implants do achieve retention from the crestal cortical bone, the presence of bone defects could be masked until it is too late to treat them.

At the University of Cartegena in Colombia and the Implant Dentistry Centre in Boston, there is significant anecdotal evidence of the anamnesis of mandibular bone defects being associated with previously failed endodontic treatments and/or traumatic tooth extractions, with signs of swelling, pain, and inflammation. Further research-based evidence may provide more telling information once enough time is allotted for long-term clinical studies to produce concrete findings.

References

1. Anusavice KL. Mechanical properties of dental materials. In: Anusavice KL. Phillips’ Science of Dental Materials, ed 10. St Louis: Elsevier Science, 2003.

2. Black GV. A Work on Special Dental Pathology. Chicago: C Ash, Sons & Company, 1915.

3. Ferguson W. New treatment of necrosis. Am J Dent Sci 1868;1:189.

4. Nelson BL. Solitary bone cyst. Head Neck Pathol 2010;4:208–209.

5. Bravo-Calderón DM, Oliveira DT, Santos dos WH. Bilateral osteoporotic bone marrow defects of the mandible: A case report. Head Face Med 2012;8:22.

6. Simancas-Pallares M, Arévalo-Tovar L, Marincola M. Focal osteoporotic bone marrow defects on dental implant treated patients: A 5-year period prevalence study. Int J Odontostomat 2016;10(1):23–28.

7. Shankland WE, Bouquot JE. Focal osteoporotic marrow defect: Report of 100 new cases with ultrasonography scans. Cranio 2004;22:314–319.

8. Theisen FC, Shultz RE, Elledge DA. Displacement of a root form implant into the mandibular canal. Oral Surg Oral Med Oral Pathol 1990;70:24–28.

9. Garcia NG, Barros FBA, Carvalho MM, Oliveira DT. Focal osteoporotic bone marrow defect involving dental implant: A case report. Int J Implant Dent 2015;1:18.

10. Lee SC, Jeong CH, Im HY, et al. Displacement of dental implants into the focal osteoporotic bone marrow defect: A report of three cases. J Korean Assoc Oral Maxillofac Surg 2013;39:94–99.

11. Bayram B, Alaaddinoglu E. Implant-box mandible: Dislocation of an implant into the mandible. J Oral Maxillofac Surg 2011;69:498–501.

12. Lamas Pelayo J, Peñarrocha-Diago M, Martí Bowen E, Peñarrocha-Diago M. Intraoperative complications during oral implantology. Med Oral Patol Oral Cir Bucal 2008;13:E239–E243.

13. Singh G, Gambhir R, Anand S, Singh S, Singh J, Singh J. Complication during implant surgery mimicking mandibular nerve damage. J Dent Implant 2015;5:110.

14. Bender IB, Seltzer S. Roentgenographic and direct observation of experimental lesions in bone. J Endod 2003;29:702–706.

15. Jeong MA, Kim SG, Kim YK, et al. A multicenter prospective study in type IV bone of a single type of implant. Implant Dent 2012;21:330–334.

16. Vickers ER, Cousins MJ. Neuropathic orofacial pain part 1: Prevalence and pathophysiology. Aust Endod J 2000;26:19–26.

17. Vickers ER, Cousins MJ. Neuropathic orofacial pain. Part 2: Diagnostic procedures, treatment guidelines and case reports. Aust Endod J 2000;26: 53–63.

18. Chadha GK, Ahmadieh A, Kumar S, Sedghizadeh PP. Osseointegration of dental implants and osteonecrosis of the jaw in patients treated with bisphosphonate therapy: A systematic review. J Oral Implantol 2013;39: 510–520.

19. Voss PJ, Joshi Oshero J, Kovalova-Müller A, et al. Surgical treatment of bisphosphonate-associated osteonecrosis of the jaw: Technical report and follow up of 21 patients. J Craniomaxillofac Surg 2012;40:719–725.

20. Shankland WE. Medullary and odontogenic disease in the painful jaw: Clinicopathologic review of 500 consecutive lesions. Cranio 2002;20:295–303.

19

Bone Regeneration: Materials and Techniques

Shadi Daher | Mauro Marincola | Dusan Poruban | Laura Murcko | John Morgan | Jeffrey Lehrberg

With applications including neurosurgery, orthopedics, and dentistry, the use of bone grafting has become an indispensable treatment for medical professionals around the world.[1] Accordingly, bone grafting has become the most commonly performed transplantation technique after blood transfusions.[1] Bone grafting is so successful because it harnesses the body’s intrinsic bone regenerative properties to allow clinicians to generate bone in deficient locations.[2,3]

Normal bone regeneration involves three important processes: osteogenesis, osteoinduction, and osteoconduction (see chapter 4). Osteogenesis describes the process wherein osteoprogenitor cells proliferate and differentiate into osteoblasts, which then subsequently deposit extracellular matrices that will act as scaffolding for the new bone.[1] The process where the molecular mechanisms induce the stimulation and recruitment of osteoprogenitor cells (ie, through intracellular and extracellular cell-signaling proteins and molecules) is called osteoinduction . Finally, osteoconduction is a term that describes the efficacy of blood vessel recruitment and osteoprogenitor cell migration to the preexisting bone structure or scaffold. Osteoconductivity is the measure of the osteoconductive quality of this scaffold.[1,3,4] Ideally, a bone-grafting material should possess osteogenic, osteoinductive, and osteoconductive properties to provide the most positive healing outcome; however, even possessing only one of these properties is enough to allow exceptional bone regeneration to occur.[1]

Bone-Grafting Materials

There are a number of materials available for clinicians who are interested in performing bone-grafting procedures, each with its own advantages and disadvantages. Choosing the right graft material is a function of personal (eg, clinician’s comfort level, familiarity with material), clinical (eg, location and degree of morbidity of the surgical site, overall health of the patient), and patient (eg, patient’s socioeconomic status, treatment preference) requirements.

The next section of this chapter reviews the following types of commonly used bone grafts: autografts, allografts, xenografts, and alloplasts. While graft choice ultimately falls to the preference of the clinician, we highly recommend either the use of autografts or alloplasts whenever possible.

although unlikely, allografts also have the potential to transmit pathogens such as HIV and hepatitis C.[1,7,8]

Xenografts

Xenografts are grafts whose material is composed of tissue derived from a donor of a dissimilar species to the patient (ie, tissue obtained from an animal or plant). Unlike most allografts, all xenografts must be decellularized to prevent an immunologic reaction in the recipient. Bone xenografts are typically derived from cancellous bovine bone because of its abundance and similarity to human cancellous bone; however, other xenograft donors include coral and marine algae. Like allografts, xenografts provide scaffolding for new bone to grow on, giving them osteoconductive properties, and in some cases may contain growth factors or other molecules that give them osteoinductive qualities.[9]

Autografts

Graft material harvested from autologous bone (typically from the mandibular symphysis, mandibular ramus, tibial plateau, calvarial bones, ribs, clavicles, or anterior and posterior iliac crests) is known as an autograft ; because of its osteogenic, osteoinductive, and osteoconductive properties, along with its decreased risk of immunologic reaction, autografts have been described as the gold standard for bone-grafting procedures.[1]

Although autologous bone possesses the ideal characteristics of a bone-graft material and is generally the best tolerated graft material by the patient with regard to immunologic reaction, it nevertheless has certain drawbacks that might dissuade its use. Harvesting autologous bone sometimes requires additional surgery, which might extend overall surgical time.[1,5] Furthermore, donor site morbidity might yield an inadequate volume of bone, or bone that is unacceptable for grafting (eg, bone affected by bacterial infection or cancer).[1,5] Nevertheless, if autologous bone can be harvested safely and without complication (eg, through the successive use of reamers, as described later in this chapter as well as in chapter 8), then it should always be the primary choice as a grafting material.

Allografts

The term allograft describes a graft that has tissues harvested from a different individual of the same species (ie, in this context, tissue from a human donor). Allograft material is available in three different forms: fresh frozen bone (FFB), freeze-dried bone allograft, and demineralized freeze-dried bone allograft. Depending on the method of preparation, allografts can possess the factors necessary to imbue them with osteogenic, osteoinductive, and osteoconductive qualities (ie, cells, growth factors, scaffolding).[3,6] A major downside to allografts is they run the risk of producing an immunologic reaction, especially with regard to FFB.[1] And

Alloplasts

In addition to the various animal tissues that have been used for grafting, a number of inorganic chemical compounds are available for bone-grafting procedures as well. Inorganic compounds or synthetic bone-grafting materials are called alloplasts ; these compounds include bioactive glasses, bioceramics, or some combination thereof (eg, glass-ceramics).[10] Bioceramics and bioglasses function as osteoconductive scaffolds that form strong bonds with the existing bone. Depending on the chemical makeup, bioceramics and bioglasses can be manufactured to be either permanent or resorbable. Moreover, through their interaction with host tissues, alloplasts have the potential to indirectly exert osteoinductive effects on their surroundings.[10] While some alloplasts may lack in osteogenic and osteoinductive potential, they eliminate the risk of disease transmission and rejection posed by autografts, allografts, and xenografts. Also, some patients may prefer to be treated with a synthetic compound as opposed to tissues obtained from human donors or animals. Finally, because they undergo rigid manufacturing processes, alloplasts are highly standardized, allowing clinicians to become familiarized with their properties and effects upon continued use.

The chemical compounds that make up bioceramics resemble the compounds that comprise bone mineral and bone precursors; typically, these materials possess some formulation of calcium phosphate (CaP) or one of its derivative chemical structures.[1,10] The physiologic effects of CaP bioceramics have been studied for almost a century and have been shown to be safe and effective in dental applications.[10–12] The two most popular bioceramics used for bone regeneration are hydroxyapatite (HA) and tricalcium phosphate (TCP).[13] TCP comes in three polymorphic forms: α, α’, and β.[11] Although the three polymorphic forms of TCP are chemically identical, β-TCP has shown excellent outcomes with regard to osteoconductive potential and β-TCP Background Fig 19-1 (a) Scanning electron microscope (SEM) image of a commercially available β-TCP with particle sizes ranging from 50 to 500 μm. (b) SEM image of SynthoGraft with particle sizes ranging from 50 to 500 μm. Observe the higher degree of porosity compared with the particles shown in a . Scale bar = 10 μm.

Fig 19-2 Human cellular response to SynthoGraft after 3 months (hematoxylin and eosin stain). Osteoblasts forming the leading edge of the new bone are indicated by the black arrow . The graft material is indicated by the asterisk . Fig 19-3 Human cellular response to SynthoGraft after 6 months (Goldner trichrome stain). Newly formed osteoid is indicated by the black arrow . The graft material is indicated by the asterisk .

Fig 19-4 (a) Representative three-dimensional (3D) microCT of trephined bone core obtained from human patients 3 months after grafting. (b) The corresponding two-dimensional section from which the 3D reconstruction was obtained in a . Here the white arrow indicates the graft material.

overall biocompatibility in both human and animal studies. For this reason, and because of their history as a successful and safe treatment modality, we recommend using β-TCP with (or as a replacement for) autologous bone.[11,14–20]

β -TCP Background

The earliest report of using β-TCP as an aid for bone regeneration was by Albee and Morrison in the early 1920s.[12,18] The use of β-TCP as a bone implant material was later expounded on and brought to the forefront of dental science by Thomas Driskell in the 1970s.[18–20] Driskell and his team began investigating the use of β-TCP as a treatment for the kind of orofacial fractures and hard tissue avulsion wounds incurred by soldiers in combat during the Vietnam War.[20]

Driskell’s original manufacturing process yielded a formula of β-TCP that was successfully used as a bone implant material under the product names Cerasorb (Curasan) and SynthoGraft (Miter) for over 20 years (Driskell TD, personal communication, 2002.). Modifications to the manufacturing process in 2005 produced Bicon’s current SynthoGraft with a more stoichiometric formula of β-TCP, which possesses particles of greater porosity (Driskell TD, personal communication, 2002.). The rationale behind SynthoGraft’s porosity is to grant enhanced resorbability via the disruption of the sintered particles that make up the material; this porosity increases surface area and has the potential to aid in bone growth and vascularization.[11,18,19,21] The porosity of SynthoGraft, as compared with another commercially available β-TCP, is illustrated in Fig 19-1.[22–24]

Human in-vivo analysis of SynthoGraft at 3, 6, and 9 months revealed increased levels of bone growth and vascularization proportional with time, suggesting that the microporosity resulting from the current formula of SynthoGraft allows for resorption and vascularization of the graft material (Fig 19-2).[23] When bone formation after sinus elevation procedures using SynthoGraft was analyzed, it was shown that there was an increase in bone growth and simultaneous decrease in graft material, again demonstrating the osteoinductive and osteoconductive attributes and resorbable nature of SynthoGraft (Fig 19-3).[24] Furthermore, microcomputed tomography (microCT) of trephined bone cores obtained from human patients 3 months after grafting revealed bone growth and bone integration into graft material in locations previously absent of bone, indicating the osteoconductive potential of SynthoGraft (Fig 19-4).[22]

Fig 19-5 SynthoGraft and autogenous bone obtained from the patient should be kept separate in a dappen dish.

Clinical Application of SynthoGraft

SynthoGraft can be used whenever existing bone needs to be augmented. Applications of SynthoGraft include internal and lateral sinus elevations, crest augmentation, and socket regeneration; furthermore, it can be used for the repair of any odontogenic, periodontal, or traumatic injury that results in areas characterized by large bone loss. Two common clinical applications for SynthoGraft include socket regeneration (also known as socket preservation ) and the guided bone regeneration (GBR) of larger bone defects—a technique that may incorporate the use of a titanium (Ti)-mesh for added support. The socket regeneration procedure is a minimally invasive technique whose aim is to preserve or reconstruct the alveolar ridge following tooth extraction. The term socket preservation —while certainly more prevalent in the literature—is somewhat of a misnomer within the field of implant dentistry, especially when the socket cannot support the immediate placement of an implant; in cases where the socket requires reconstruction, the goal is not preservation of the void, but rather regeneration of the alveolar ridge. GBR with support is a technique employed for larger bone defects such as those that occur as a result of traumatic bone loss or extreme periodontal disease.[25–28]

GBR uses a membrane that acts as a mechanical barrier between the desired slow-growing bone tissues and fast-growing connective and epithelial tissues. The end goal of the GBR procedure—as it pertains to this chapter—is the creation of adequate bone volume to permit the placement of implants or to stabilize and allow bone growth over an exposed implant after placement.[25–28]

The remainder of this chapter focuses on the preparation and use of SynthoGraft for both socket regeneration and the more extensive GBR techniques.

Preparation guidelines

Preparing SynthoGraft is simple and straightforward. First, the patient’s blood (obtained at the surgical site) is added to an empty dappen dish, followed by the progressive addition of SynthoGraft particles. The SynthoGraft and blood are then mixed together in the dappen dish with a periosteal elevator or similar instrument. The final mixture of blood and SynthoGraft should have a putty-like consistency. If the initial mixture is too wet, it can be patted with a sterile wipe, or more SynthoGraft may be added. If it is too dry, the desired consistency can be obtained by adding more blood.

During the surgical procedure, any autologous bone that is collected should be kept separate from the SynthoGraft preparation; this can be easily achieved by keeping autologous bone on the side of the dappen dish and the SynthoGraft preparation (ie, blood and SynthoGraft) on the very bottom of the dish (Fig 19-5). Autologous bone is preferred to SynthoGraft for grafting because of its osteogenic and osteoconductive properties (ie, autologous bone has patient-derived osteoprogenitor cells and growth factors, whereas SynthoGraft does not). Autologous bone with its superior characteristics should be used to fill as much of a bony defect as possible before the addition of SynthoGraft. Furthermore, separating SynthoGraft from autologous bone prevents the possibility of sudden changes in pH and osmolarity, which has the potential to harm the osteoprogenitor cells in the collected autologous bone (Driskell TD, personal communication, 2002.).

Socket Regeneration

Subsequent to tooth extraction, bone located immediately adjacent to the socket will diminish in volume—so much so that within the first 12 months, as much as 5 to 7 mm of bone can be lost along the buccopalatal axis.[29–31] In total, after the first year, nearly 50% of the crestal bone volume surrounding extraction sites has been reported as having the potential of being lost following tooth extraction.[29–31] Briefly, bone is lost after tooth extraction because the periodontal ligament and surrounding bundle bone lose their functionality, and osteoclast activity at the extraction site causes the bone to resorb.[30,32–34]

To prevent the resorption of crestal bone following extraction and preserve the alveolar crest, there are two main treatment modalities that can be pursued: immediate implant placement or socket regeneration (if there is no intent to place an implant for an extended period of time). The decision to immediately place implants or perform socket regeneration techniques should be based on the patient’s health and socioeconomic status, socket and surrounding bone morphology, extent of injury, and the clinician’s preference.[30,31,34,35] A simple guide outlining our treatment recommendations based solely on extraction site can be found in Table 19-1.

If an atraumatic extraction exposes healthy bone and the site suggests it can support an implant with a low risk of movement and can bear a nonloading provisional restoration, then the immediate placement of implants is recommended.[36–38] However, if the health of the socket, alveolar bone, or surrounding periodontium is questionable; the temporization

Table 19-1 Treatment recommendations based on extraction site

is not optimal or will require extensive preparation and time; and/or the extraction was traumatic, then a delayed immediate approach is recommended. The delayed immediate approach may call for the implementation of GBR techniques after a 6- to 8-week postextraction healing period. Finally, implant placement should be delayed for a period of 4 to 6 months for residual bone defects that require the implementation of GBR procedures using a membrane.

Socket regeneration of maxillary central incisor

A 72-year-old man with no significant prior medical history presented with a fractured maxillary left central incisor and concomitant bone loss, as indicated by discolored and distorted gingiva and open margin at the mesial crown-root junction (Figs 19-6a and 19-6b). The crown of the affected tooth was carefully removed prior to introducing a straight periotome into the periodontal ligament space as deeply as possible (Figs 19-6c and 19-6d). Luxators were then used to mobilize the remaining root structure (Fig 19-6e). Once the root was fully mobilized, it was easily removed with soft tissue forceps (Fig 19-6f). It is important to note that great care should be taken when luxating and removing the root to minimize its movement against the thin buccal plate; nevertheless, damage of the buccal plate can still occur, as was the case during this treatment. Fig 19-6 (cont) (g) Curetting the socket reveals the loss of the bone. (h) Removal of granulation tissue with forceps. (i) Blood is collected with a syringe for later use as a wetting agent for SynthoGraft. (j) The buccal bone defect is covered with a collagen barrier membrane. (k) Blood is mixed with SynthoGraft particles using a 4.0-mm Bone-Graft Syringe. (l) SynthoGraft is injected into the socket with a 4.0-mm Bone-Graft Syringe. (m) Appearance of the socket after it has been filled with SynthoGraft. (n) After the socket is filled, the collagen membrane is folded over the graft. (o) A collagen plug is placed over the graft. —

The damaged buccal plate was revealed while curetting the socket; therefore, a delayed immediate approach via socket regeneration was pursued (Fig 19-6g). Granulation tissue was removed to expose the available bone and to allow the assessment of the defect (Fig 19-6h). Around 0.25 to 0.5 mL of blood was collected from the site for later use as a wetting agent for SynthoGraft (Fig 19-6i). To compensate for the buccal wall defect, a collagen barrier membrane was inserted in the socket (Fig 19-6j). Next, SynthoGraft was prepared using the previously collected blood and injected into the socket with a 4.0-mm Bone-Graft Syringe (Figs 19-6k to 19-6m). After the socket was filled with SynthoGraft, the collagen membrane was folded over the SynthoGraft particles and covered with a collagen plug (Figs 19-6n and 196o). The purpose of the collagen plug is to facilitate primary wound closure by providing a scaffold for migrating epithelial cells; it also provides temporary mechanical protection during healing, which eliminates the need for harvesting soft tissue from the palate. The collagen plug was then secured using a horizontal mattress suture along with a few drops of surgical glue for added stability and promotion of hemostasis (Figs 19-6p to 19-6r). Radiographs taken at implant placement and uncovering (at 5 and 9 months, respectively) demonstrate the success of the socket regeneration procedure, as indicated by healthy bone (Figs 19-6s to 19-6u).

Socket regeneration of mandibular central incisor

A 69-year-old man with cardiac disease, hypertension, and diabetes was referred for multiple infected, carious, and fractured teeth. The socket regeneration treatment presented here posed difficulty because of the severely constrained space between adjacent and similarly compromised teeth (Figs 19-7a and 19-7b). To begin the procedure, straight and curved periotomes were used to sever the periodontal ligament, and the root was easily extracted using small soft tissue forceps (Figs 19-7c and 19-7d). While Fig 19-7 (a) Preoperative periapical radiograph showing the endodontically treated mandibular central incisor. (b) Preoperative clinical view of the fractured mandibular central incisor. —_,

curetting the granulation tissue (Fig 19-7e), a thin buccal plate defect extending the length of the root and fenestration at the apex were discovered. This compelled a delayed immediate approach. A collagen barrier membrane covering the entire length of the bony defect was inserted, followed by the preparation and injection of SynthoGraft into the socket (Figs 19-7f to 19-7h). The membrane and graft material were secured and stabilized by inserting a portion of a collagen plug prior to performing a horizontal mattress suture (Figs 19-7i to 19-7k). A 7-year follow-up radiograph shows that the bone has remained stable at the location of implants and retained teeth (Fig 19-7l).

Socket regeneration: Xenografts versus SynthoGraft

When a socket can support the immediate placement of an implant, experience has shown that immediate implant placement without first doing a socket regeneration procedure affords the best way to preserve the extant bone in the alveolar ridge with Bicon implants. Clinical experience has also shown that the rapidity of bone resorption does not justify many socket-preservation procedures. A significant number of implants can be routinely placed 3 or more years after a tooth has been extracted without any socket-preservation procedure. Fig 19-7 (cont) (c)(c) A straight periotome is used to sever the periodontal ligament. (d) The root is removed with forceps. (e) Granulation tissue is removed with a curette. (f) SynthoGraft is mixed with the patient’s blood to a putty-like consistency. (g) A collagen barrier membrane is tried prior to being trimmed, curved, and inserted into the socket against the entire length of the bony defect. (h) SynthoGraft is injected into the socket with 4.0-mm Bone-Graft Syringe. (i) A section of collagen plug is inserted to protect and stabilize the membrane and graft. (j) Stabilizing the collagen plug and graft with a horizontal mattress suture. (k) Postoperative radiograph after the socket regeneration procedure. (l) Seven-year follow-up radiograph of socket regeneration site showing stable bone at the location of the implants and retained teeth.

The logic of grafting an entire socket must be called into question when similar effects regarding implant stability and success can be accomplished without any grafting or only grafting the socket orifice—the location where initial resorption occurs. Furthermore, the decision to perform socket-regeneration techniques should be based primarily on the patient’s needs and welfare and not on the fact that a treatment can be done.

In consideration of patients’ long-term health and welfare, caution should be exercised when using xenografts as a bone-grafting material. The overall success and popularity of xenografts notwithstanding, analyses of both their short- and long-term effects in extraction sockets suggests a possible deleterious influence.[39–42] Early healing experiments evaluating the effect of xenografts in extraction sockets demonstrated connective tissue enclosure around the graft at 2 weeks, as opposed to the presence of woven bone in the controls without grafts at equivalent times. This result suggests that xenografts may interfere with early healing events.[39,43] The connective tissue enclosure observed surrounding xenografts is indicative of a possible foreign body reaction, a response that has the potential to delay intrinsic healing events during socket regeneration.[44] Pagni et al[39] speculated that the patient’s own cells and regeneration-promoting factors would have occupied the socket had they not been precluded by the presence of the xenograft material.

Several authors have reported only partial resorption of xenografts, a condition that could potentially lead to implant failure.[39,43,45–50] Araújo et al[51] showed that despite possessing a higher number of mineralized tissue figures, bone formation in bovine xenografts after 3 months appeared similar to that seen in nongrafted sites.[39] Moreover, some authors speculate that in some instances, a xenograft may never fully resorb.[39,49] Even more concerning is the potential for long-term complications such as infection and failure of the implant to osseointegrate. For the foregoing reasons, the use of synthetic bone-grafting materials is recommended over xenografts. Fig 19-8 (a) Radiograph depicting implant placed immediately after extraction with no graft. (b) Radiograph taken 3 months after extraction and immediate placement of the implant. (c) Radiograph taken 4 months after extraction and placement. (d) Radiograph taken 10 years after extraction and placement revealing excellent bone healing without any grafting. (e) Radiograph depicting a socket-regeneration procedure with SynthoGraft. (f) Radiograph taken 6 months after the postextraction socket-regeneration procedure revealing significant resorption of the SynthoGraft material. (g) Radiograph taken 13 months after the grafting of the extraction socket with little or no evidence of remaining SynthoGraft. (h) Radiograph taken 2 years and 2 months after grafting the extraction socket. No evidence remains of any SynthoGraft, suggesting that it has been completely resorbed.

To further illustrate the differences in bone regeneration when comparing the use of a xenograft with either SynthoGraft or an immediate implant placement with no graft, the following three treatments are presented. The first treatment depicts an immediate implant placement without any graft material into the mandibular left first molar extraction socket of a 68-year-old woman. The second treatment depicts an immediately placed implant into the mandibular left first premolar of the same patient, only this time the socket had been previously grafted 6 months earlier with SynthoGraft. The first and second treatments can be compared with the third treatment, which depicts a patient who had a socket regeneration procedure with a xenograft 2 years and 4 months prior to the placement of an implant into the native bone of the furcation between the two grafted root sockets.

In the treatment showing an immediately placed implant with no graft, a 68-year-old woman had an implant immediately placed in the extraction site of the mandibular first molar (Fig 19-8a). Three months later, healthy bone could be seen around the implant (Fig 19-8b). Four months after extraction and placement of the implant, the Integrated Abutment Crown (IAC) was placed; the radiograph revealed that the bone surrounding the implant was still healthy (Fig 19-8c). At a 10-year follow-up, radiographs revealed that the bone around the implant was mature (Fig 19-8d).

In the same patient, the mandibular left premolar socket had been grafted with SynthoGraft (Fig 19-8e). The 6-month radiograph reveals significant resorption of the SynthoGraft material (Fig 19-8f). Over a period of 13 months, the SynthoGraft material in the socket site continued to be resorbed, and at the time of the implant’s uncovering, there was little or no evidence of the SynthoGraft material (Fig 19-8g). The 26-month follow-up radiograph shows no evidence of the SynthoGraft, suggesting its complete resorption (Fig 19-8h).

Fig 19-9 (a) Cone beam computed tomography (CBCT) scan of a first molar socket immediately after placement of a xenograft. (b) Radiograph taken 2 years and 4 months after placement of a xenograft into a molar socket revealing virtually no resorption of the xenograft. Additionally, note that the implant was placed into the native bone of the furcation between the grafted roots and not into the graft material. The third treatment shows a 72-year-old woman who had a xenograft placed at the time of the extraction (Fig 19-9a). An implant was placed into the native bone of the furcation between the grafted root sockets over 2 years later. In this example, the presence of the xenograft was readily observable, even after 2 years. Despite the fact that the second patient’s xenograft had been in situ for so long, there was no radiographic evidence of the xenograft’s resorption (Fig 19-9b).

The bone regeneration shown in the first patient, whose molar implant healed without a graft and whose premolar implant was previously treated with a SynthoGraft socket regeneration procedure, stand in stark contrast to the lack of resorption of the xenograft material in the second patient. The results shown in Fig 19-9b question the wisdom of routinely grafting sockets and the imprudence of using xenografts, especially when compared with bone regeneration seen when using SynthoGraft or no graft at all.

GBR for Large Bone Defects

Treatments characterized by large bone defects require GBR (see Table 19-1). When GBR is pursued as the treatment of choice, immobilization and protection of the graft are paramount. If the tissue surrounding the location of the intended GBR site provides enough support to ensure the stability and protection of the graft, then GBR can be achieved using a soft barrier membrane to surround the graft material. However, if the location of the GBR site does not have adequate adjacent tissue or exposes the graft to mechanical disturbances, then a rigid crib or reinforced membrane is required to protect against soft tissue encroachment and movement of the graft. The following treatments illustrate how the location of deficient bone and the quality of surrounding tissue dictate the use of a soft collagen barrier membrane or rigid crib support.

GBR in a maxillary lateral incisor site

The same patient discussed in the socket regeneration of a mandibular central incisor (see Fig 19-7) also required GBR for a maxillary right lateral incisor (Fig 19-10a). After the abscessed maxillary right lateral incisor was removed, the area was allowed to heal for 8 weeks (Figs 19-10b and 19-10c). After 8 weeks, it was revealed that the bone defect had not healed sufficiently, so it was filled with granulation tissue. Fortunately, the surrounding tissue was relatively well preserved and could support GBR.

A full-thickness mucoperiosteal flap was elevated, and curettes were used to remove the granulation tissue and callus that had formed in the bony defect (Fig 19-10d). Soft tissue rongeurs were then used to remove any remnants of soft tissue callus (Fig 19-10e). Next, a pilot drill with external irrigation was used to create an osteotomy to initiate the placement of an implant in the site of the missing tooth (Fig 19-10f). Successive Hand Reamers were then used to expand the osteotomy to the final implant diameter (Fig 19-10g). SynthoGraft was mixed with the patient’s blood and injected into the surgical site using a 4.0-mm BoneGraft Syringe (Fig 19-10h). After injecting the SynthoGraft, an Inserter/Retriever was used to place and position the implants while simultaneously adding SynthoGraft to enhance stability (Fig 19-10i). Following the placement of the implants, the black Healing Plugs were placed and trimmed (Fig 19-10j). A retention suture was then prepared, and SynthoGraft was positioned over the exposed surface of the implant in the lateral incisor site (Fig 19-10k). A trimmed resorbable collagen barrier membrane was positioned over the defect, and the retention suture was tightened to secure the membrane and graft in the proper location (Fig 19-10l). Finally, the site was closed using a continuous 4.0 chromic gut suture (Figs 19-10m and 19-10n). Six months after placement, the surgical site exhibited stable bone (Fig 19-10o). The bone remained stable, as shown in radiographs 6 and 9 years later (Figs 19-10p to 19-10r). Fig 19-10 (a) Preextraction radiograph showing carious teeth with periapical radiolucencies. (b) Postextraction radiograph showing the large radiolucency at the site of the missing lateral incisor. (c) Appearance of maxillary incisor site 8 weeks after extraction. (d) A full-thickness periosteal flap was elevated, and the underlying granulation tissue and soft tissue callus are removed. (e) Soft tissue callus and granulation tissue is removed with soft tissue rongeurs. (f) Pilot drill with external irrigation is used to initiate the osteotomy. (g) Expanding the osteotomy with final 5.0-mm Hand Reamer. (h) Injecting SynthoGraft with a 4.0-mm Bone-Graft Syringe. (i) Inserting the implant with Inserter/Retriever instrument. Inserting the implant further compresses the graft, making it more stable. (j) Implants with trimmed black Healing Plugs. (k) SynthoGraft was placed over the exposed implant in the lateral incisor site. (l) Securing the collagen barrier membrane over SynthoGraft. —_, Fig 19-10 (cont) (m) Appearance of surgical site after closure. (n) Postoperative radiograph. (o) Six-month follow-up radiograph taken at time of uncovering. (p) Clinical appearance 3 months after placement of restorations. (q) Radiograph taken 6 years after placement. (r) Radiograph taken 9 years after placement.

GBR in a maxillary premolar site

A 53-year-old man with noncontributory prior medical history presented with a loose and tender maxillary right second premolar (Fig 19-11a). The badly abscessed premolar was diagnosed and removed. A periapical radiograph following extraction revealed the true extent of the bone defect (Fig 19-11b). After the extraction, a 6-week healing time was prescribed, which allowed only for the formation of soft tissue callus and no bone (Fig 19-11c). A papilla-sparing, paddle-shaped mucoperiosteal flap was raised, which exposed and confirmed the full extent of the bony defect seen in the radiograph (Fig 19-11d). Moreover, using a 6.0-mm-wide Hand Reamer revealed that there would be no contact available between the walls of the defect and the largest available implant (Fig 19-11e).

To repair the defect, SynthoGraft was prepared and injected into the surgical site and then packed with small periosteal and Freer (Sklar) elevators (Figs 19-11f and 19-11g). Next, an Inserter/Retriever instrument was used to position the implant tightly within the graft at the center of the defect, followed by the placement and trimming of the black Healing Plug (Fig 19-11h). The remaining SynthoGraft was then packed with a sterile Cotton Tip Applicator around any exposed implant surfaces (Fig 19-11i). A resorbable collagen barrier membrane was then trimmed and positioned over the graft and defect (Fig 19-11j). To secure the surgical site, a horizontal mattress retention suture was passed from the palatal surface to the depth of the flap, where it entered through the tethered periosteal tissues and exited out of the palatal surface, where it was then tied (Fig 19-11k). This suture configuration sufficiently immobilized the membrane and underlying graft particles in their correct positions. The flap was then closed with 4.0 chromic gut sutures (Fig 19-11l). A postoperative radiograph was taken to ensure correct implant placement (Fig 19-11m). A radiograph taken 5 months after implant placement at the time of uncovering showed what appeared to be stable bone; this was confirmed by the surgical uncovering (Figs 19-11n and 19-11o). Finally, as shown in the clinical and radiographic images, the bone derived from the graft, as well as the implant, have remained stable (Figs 19-11p and 19-11q). Fig 19-11 (a) Periapical radiograph of maxillary right second premolar showing large periapical radiolucency extending to the apex of the first premolar and into the bony crest. (b) Postextraction radiograph showing size of bony defect. (c) Preoperative appearance of surgical site showing excellent healing of soft tissue with minimal shrinkage. (d) Raising the mucoperiosteal flap exposes the full extent of the bony defect. (e) Inserting the widest Hand Reamer (possessing the same diameter as the widest implant) shows that the implant will be unable to make contact with the bony walls of the defect after the preparation of an osteotomy. (f) SynthoGraft is injected into the defect site with a 4.0-mm Bone-Graft Syringe. (g) A trimmed black Healing Plug is placed in the implant well with a periodontal probe. (h) SynthoGraft is condensed around the exposed surfaces of the implant. (i) The remaining SynthoGraft is packed around any remaining exposed implant surfaces with a sterile cotton swab. (j) A resorbable collagen barrier membrane is placed over the graft. (k) A horizontal mattress suture is used to secure the graft. (l) Clinical appearance of the surgical site after closure. (m) Postoperative radiograph taken to confirm correct implant placement. (n) Radiograph taken 5 months after implant placement. (o) Appearance of the healed grafted bone during the uncovering of the implant. (p) Six-month clinical view of the IAC after placement. (q) Six-year postoperative radiograph. Fig 19-12 (a) Preoperative radiograph showing the maxillary left quadrant. (b) Another radiographic view of the maxillary left quadrant. Note the proximity of the maxillary sinus to the defect. (c) Elevating a full-thickness flap revealed a bone defect and granulation tissue in the premolar site. (d) Granulation tissue is removed. (e) Appearance of the crest following removal of granulation tissue. (f) Clinical image of two paralleling pins in pilot osteotomies while a third osteotomy is being drilled. (g) Osteotomy is widened. (h) Harvested bone is visible within the flute of a Hand Reamer as it is removed from the osteotomy. (i) An Implant Inserter/Retriever instrument is used to place a 4.0 × 8.0–mm implant in the site of the lateral incisor. —_>

GBR in maxillary canine and premolar sites

A 57-year-old woman presented with a failed denture involving her maxillary left lateral incisor, canine, and first premolar, along with persistent pain following the removal of the first premolar. Preoperative radiographs revealed bone defects resulting from the extraction of the teeth and the absence of the buccal wall (Fig 19-12a). Furthermore, the defects had notable proximity to the maxillary sinus (Fig 19-12b). Raising a full-thickness flap confirmed the presence of bone defects along with ensuing granulation tissue in the location of the extracted premolar (Fig 19-12c). The granulation tissue was removed with a curette, which further revealed the extent of the bone defect (Figs 19-12d and 19-12e). Next, a pilot drill was used to initiate the osteotomies in the sites of the maxillary left lateral incisor, canine, and first premolar (Fig 19-12f).

Following the initial drilling of the osteotomies, successively wider Hand Reamers were used to expand the osteotomy’s diameters in 0.5-mm increments to allow for the placement of implants (Figs 19-12g to 19-12i). Because of the defect, implants could only be placed in the lateral incisor and canine sites without GBR (Fig 19-12j). First, using Hand Reamers, the osteotomy at the location of a premolar was expanded, and autologous bone was saved in the dappen dish (Fig 19-12k). Then, the sinus floor was mobilized using a 5.0-mm sinus elevation osteotome (see chapter 12) (Figs 19-12l and 19-12m). Next, SynthoGraft was mixed with the patient’s blood and injected into the osteotomy with a 4.0-mm Bone-Graft Syringe (Figs 19-12n and 19-12o). Once the osteotomy had been filled with SynthoGraft, an implant was gently placed at the mouth of the osteotomy and tapped into place (Fig 19-12p); this further condensed the graft and elevated the sinus floor. After placing the implant in the site of the first premolar, its surface remained exposed because of the missing buccal plate (Fig 19-12q). Black Healing Plugs were placed and trimmed, followed by a horizontal releasing incision in the periosteum at the depth of the flap (Fig 19-12r). Autologous bone collected during reaming was then placed over the exposed implant surface, followed by the application of the remaining SynthoGraft (Figs 19-12s and 19-12t). A resorbable collagen barrier membrane was then placed over the canine and premolar implant sites and secured in place with a retention suture (Fig 19-12u). Fig 19-12 (cont) (j) Implant placed in the canine site. A guide pin in the site of the lateral incisor indicated the angle of the osteotomy. Note the extent of the buccal defect in the osteotomy at the first premolar site. (k) Hand Reamers were used to expand the osteotomy at the site of the first premolar. (l) A 5.0-mm sinus elevation osteotome was used to mobilize the sinus floor. (m) Appearance of the sinus floor after mobilization with Osteotome. (n) Injecting SynthoGraft into the osteotomy with a Bone-Graft Syringe. (o) Appearance of osteotomy after injecting SynthoGraft. (p) Tapping a 5.0 × 6.0–mm implant into place while simultaneously elevating the sinus floor. (q) Clinical image of an implant seated in the premolar site with partial exposure of its surface. (r) Horizontal releasing incision is made in the periosteum at the depth of the flap. (s) Autogenous bone was applied over the exposed implant surface. (t) SynthoGraft was layered over the autogenous bone. (u) A collagen barrier membrane is secured over the canine and premolar implants with a retention suture. (v) Postoperative radiograph showing implant placement and location of sinus floor above first premolar implant. (w) Five-month postoperative periapical radiograph. (x) Uncovering of implants after 5 months revealed healed bone over the exposed implant surface. (y) Periapical radiograph showing implants with definitive abutments 1 month after uncovering.

The postoperative radiograph confirmed the placement of the implants and the successful elevation of the sinus floor (Fig 19-12v). After 5 months, the patient returned for the implant uncovering; a periapical radiograph indicated stable bone in the area of the defect, which was later confirmed during the uncovering (Figs 19-12w to 19-12y).

a b c d e eis ln. f g h i Fig 19-13 (a) Preoperative radiograph of maxillary left first premolar with significant periapical radiolucency. (b) Clinical image of significant alveolar bone defect after removal of first premolar and periapical granuloma. (c) Clinical image of sutured site after placement of implant with 1.0 g of SynthoGraft and coverage with a resorbable collagen membrane. (d) Radiograph after placement of 4.5 × 8.0–mm implant with SynthoGraft. (e) Radiograph 4 months after implant placement. (f) Clinical image 4 months after implant placement, at the time of implant uncovering. (g) Clinical image of uncovered implant. (h) Clinical image of green acrylic sleeve on 3.0-mm impression post for the making of a full-arch implant-level transfer impression. (i) Clinical image of IAC seated in implant. (j) Radiograph after placement of IAC. (k) Radiograph after 4 years of function. (l) aT j k l Radiograph after 5 years of function. GBR in maxillary premolar site 19-13g and 19-13h). Clinical and radiographic images after the placement of the IAC confirmed the successful treatment of A 55-year-old woman without a history of significant health isthis immediately placed implant in a compromised surgical site sues or medications presented with a complaint of intermittent (Figs 19-13i and 19-13j). Further credence to the efficacy of this pain in one of her teeth. Clinical and radiographic examinations treatment is given by the 4- and 5-year radiographs (Figs 19revealed periapical radiolucency and a sinus tract over her max13k and 19-13l). illary left first premolar, which also had a 12.0-mm facial pocket (Fig 19-13a). Because of time constraints, it was decided to extract her premolar and immediately replace it with an implant GBR in a mandibular lateral incisor site using a GBR procedure. Fortunately, the periapical granuloma was removed in its entirety with the extracted tooth. A full-thickA 72-year-old man presented with a complaint of pain ness flap was raised, and the extraction site was curetted (Fig while chewing. The patient had a history of hypertension 19-13b). Because the surgical defect was larger than the largest and cardiac arrhythmia. The examination and initial radiopossible osteotomy, the site was minimally prepared and filled graph revealed that the endodontically treated mandibular with a 1.0-g mixture of blood and SynthoGraft, along with a 4.5 left lateral incisor had a split root (Fig 19-14a). The remain× 8.0–mm implant. The implant and mixture were subsequently ing mandibular anterior incisors were quite mobile, and the covered with a resorbable collagen barrier membrane, and the ideal treatment plan called for their removal. However, besite was closed with resorbable sutures (Fig 19-13c). The postcause of his insistence and travel schedule, the treatment operative radiograph revealed the favorable positioning of the involved only the fractured incisor. The tooth was extractimplant and extent of the grafting (Fig 19-13d). After 4 months, ed, and the socket was thoroughly curetted. Evaluation of the radiographic and clinical images indicated a successful the socket revealed that the facial wall was entirely missing, treatment (Figs 19-13e and 19-13f). The implant was uncovindicating that the starting point of the osteotomy would ered, and a green 3.0-mm impression post with a correspondhave to be at the base of the socket, and likely even deeping acrylic sleeve was inserted into the well of the implant for er. Following the placement of a 3.0 × 6.0–mm implant, the making of a full-arch implant-level transfer impression (Figs the upper half of the implant shoulder remained exposed.

19-13g and 19-13h). Clinical and radiographic images after the placement of the IAC confirmed the successful treatment of this immediately placed implant in a compromised surgical site (Figs 19-13i and 19-13j). Further credence to the efficacy of this treatment is given by the 4- and 5-year radiographs (Figs 1913k and 19-13l).

A 72-year-old man presented with a complaint of pain while chewing. The patient had a history of hypertension and cardiac arrhythmia. The examination and initial radiograph revealed that the endodontically treated mandibular left lateral incisor had a split root (Fig 19-14a). The remaining mandibular anterior incisors were quite mobile, and the ideal treatment plan called for their removal. However, because of his insistence and travel schedule, the treatment involved only the fractured incisor. The tooth was extracted, and the socket was thoroughly curetted. Evaluation of the socket revealed that the facial wall was entirely missing, indicating that the starting point of the osteotomy would have to be at the base of the socket, and likely even deeper. Following the placement of a 3.0 × 6.0–mm implant, the upper half of the implant shoulder remained exposed. Fig 19-14 (a) Preoperative radiograph showing an endodontically treated mandibular left lateral incisor with a split root. (b) At the uncovering 2 years later, a periapical radiograph showed the implant and graft in place. (c and d) The following month, the implant was restored with an IAC. The radiograph taken at the time of placement shows a radiolucent area extending from the head of the implant to the crestal bone. (e) Two-year postoperative radiograph showing stable bone levels and the all but resolved radiolucent area. (f) Three-year clinical view shows healthy gingiva around the right lateral incisor IAC.

To remedy this, a mixture of the patient’s blood and SynthoGraft was prepared and injected into the socket. A significant amount of SynthoGraft was required to cover the exposed implant shoulder and fill the defect. Next, the graft was covered with a resorbable collagen membrane and a collagen plug. A radiograph was taken at the uncovering 1 year later, showing the graft and implant in place (Fig 19-14b).

The following month, the implant was restored with an IAC (Figs 19-14c and 19-14d). A radiograph taken at the time of placement showed a radiolucency extending from the head of the implant to the crest of bone (see Fig 19-14c). Radiographs taken 2 years later displayed healthy soft tissues with the radiolucent area all but resolved (Fig 19-14e). The patient also reported that he was eating well without any discomfort.

Three years after implant placement, clinical images and radiographs revealed remarkable tissue and bone healing; this was significant considering the seemingly adverse crown-to-implant ratio, depth of implant placement, short implant size, and volume of SynthoGraft used (Fig 19-14f).

GBR in mandibular molar sites

With the successful use of the 5.0-mm short implants, it became apparent that GBR procedures could be an efficient and practical alternative to the two-stage mandibular ridge-splitting techniques for the placement of implants in thin mandibular ridges (see chapter 13). There have been multiple clinical successes over the last 5 years that demonstrate GBR’s reliability as an alternative to ridge-splitting procedures, and the following are three examples. The treatment includes intentionally only partially seating an implant in an osteotomy and covering the exposed buccal aspect of the implant with SynthoGraft and a resorbable collagen membrane.

There are three prerequisites for this treatment modality: First, is there adequate height of crestal bone to accommodate the full length of the implant? Second, is there adequate clearance and volume of basal bone above the mandibular nerve to accommodate two or three plateaus of the implant? Third, is there adequately thick and unscarred soft tissue to provide good vascularity for an envelope flap, since scar tissue increases the risk of an incision breakdown? All of these features must be present to safely proceed with this treatment.

The actual technique consists of a crestal incision for a full-thickness flap incorporating the buccinator muscle with a very careful and conservative dissection to create a small pocket-like space, which will help contain the graft particles. The pilot osteotomy should be against the length of the lingual plate, and the osteotomy should be prepared to its full depth and width. In very dense Type I bone, consider using the largest reamer several times to facilitate the complete seating of the implant. The collagen membrane should be well trimmed so that it fits snugly in the pocket without overlapping the crest. Or, if placed over the crest, it should be neatly tucked under the lingual tissue. Mix the SynthoGraft particles with the patient’s blood to a putty-like consistency prior to placing the membrane in the pocket inside the flap. Initially, cover the exposed implant and crestal bone with autogenous bone prior to completely filling the created space between the membrane and bone with as much SynthoGraft as practical. The surgical site closure should be tension-free before manually compressing the flap and graft to fill the spaces between the implant’s plateaus and to eliminate any dead space under the flap. Allow 5 months of healing before restoring the implant. Fig 19-15 (a) Preoperative clinical image. (b to d) Preoperative radiographic image and CBCT of right molar sites with the intended implant superimposed in green . (e) Full-thickness flap has been reflected. (f) Patient’s blood is collected to be mixed with SynthoGraft to a putty-like consistency for grafting prior to closure of the surgical site. (g) Second 2.0-mm pilot osteotomy is prepared parallel to adjacent gold parallel pin. (h) Two parallel pins seated in pilot osteotomies indicating their trajectories. (i) A gold 2.5-mm Hand Reamer attached to a threaded instrument adapter is used to widen the pilot osteotomy because it provides greater control than the double-fluted Latch Reamer. (j) Harvested bone in the single flute of the Hand Reamer. (k) Depth gauge indicating the difference in the osteotomy’s lingual and buccal depths. (l) Dense type I bone being harvested in reamer flute. —_> >

Treatment 1

The first treatment presented is of a 61-year-old man with a noncontributory medical history, who desired to replace his mandibular right second premolar and first molar with two implants (Figs 19-15a to 19-15d). After appropriate clinical and radiographic evaluations, it was decided to place a 4.5 × 6.0–mm implant in the second premolar site and a 5.0 × 6.0–mm implant in the first molar site. The surgical technique as described above was followed except that only autogenous bone was used without SynthoGraft (Figs 1915e to 19-15u). Radiographs of the implants taken immediately after they were placed and then again after being in function for over 4 years attest to the efficacy of intentionally only engaging a couple of the implant plateaus in an osteotomy and subsequently covering the exposed portions of the implant with GBR procedures (Figs 19-15v to 19-15z).

Treatment 2

The second treatment was of a 56-year-old woman who also had a noncontributory medical history. She presented with an edentulous and atrophic left mandible distal to her first premolar (Figs 19-16a to 19-16c). Although surgical treatment was essentially the same as the previous treatment, and as described in the introduction, it was different in the initiation of the pilot osteotomy because of the very thin and dense crestal bone (Fig 19-16d to 19-16bb). Once again, the radiographic and CBCT scan images after almost 5 years in function are evidence of the predictability and reliability of GBR procedures in lieu of mandibular ridge-splitting procedures (Figs 19-16cc to 19-16ee). Fig 19-15 (cont) (m) Implant is placed into distal osteotomy. (n) Clinical view of mesial osteotomy and seated distal implant with Healing Abutment. (o) Two seated implants with exposed plateaus and shoulder of the mesial implant. (p) Healing Plug being cut. (q) Two seated implants with exposed buccal shoulders. (r) Collagen membrane is fitted over implants to fit neatly within envelope flap. (s) Autogenous bone is placed over the implants prior to the collagen membrane. (t) Clinical image of collagen membrane positioned over the bone graft. (u) Clinical image of tension-free sutured closure after compression of graft material to eliminate any dead space. (v) Postoperative radiograph. (w) Radiograph after 4 years in function. (x and y) Postoperative CBCT scans after 5 years in function revealing thicker buccal bone. (z) Postoperative clinical view after 5 years in function revealing healthy soft tissue despite heavy tobacco use as evidenced by staining.

Fig 19-16 (a) Preoperative radiographic view. (b) Preoperative CBCT scan with intended implant placement in green . (c) Preoperative clinical view. Note the narrow band of keratinized tissue overlying the significant saddle deformity. Fig 19-16 (cont) (d) Crestal incision with mesial releasing curve that spares the keratinized tissue. (e) Full-thickness mucoperiosteal flap with additional lingual reflection. (f) Periodontal probe is used to demonstrate the pouch or pocket space, which will accommodate buccal grafting material. (g) Because of the extreme atrophy of the crest resulting in fusion of both cortices, a high-speed surgical drill is used to initiate the pilot osteotomy. (h) The crestal cortical bone is shaped by using a succession of Latch Reamers at high speed with copious sterile irrigation. (i) A straight paralleling pin is used to verify position and angulation of the pilot osteotomy. (j) The pilot osteotomy is completed with a Hand Reamer mounted on a threaded instrument adapter while rotating at 50 rpm. This allows a precise and very safe placement of the osteotomy near sensitive structures such as the mandibular nerve. The osteotomy is then completed by using successively larger Hand Reamers attached to a threaded instrument adapter. (k) The harvested bone is collected within the flute of a Hand Reamer. (l) A 4.5 × 6.0–mm Integra-CP implant is inserted with its black Healing Plug and carrier. (m) After the implant is initially seated, the Healing Plug is removed from the well of the implant. (n) An offset driver with the appropriate seating tip is used to finalize the implant seating within the osteotomy. (o) The black Healing Plug was cut extraorally and placed in the implant well with a periodontal probe. (p) The implant with its cut Healing Plug is subcrestally positioned on the lingual and supracrestally positioned on the buccal, and a trimmed collagen resorbable barrier membrane is introduced under the flap. (q) Care should be taken to avoid herniating any particles into the soft tissues or beyond the dissected edges of the flap. The autogenous bone graft was initially placed contiguous with the implant and bone, and it subsequently covered with SynthoGraft. (r) While securing the membrane in place, the previously mixed SynthoGraft and blood from the surgical site are injected into the space between the membrane covering the ridge and the exposed portion of the implant. —_,> Fig 19-16 (cont) (s)(s) Clinical image of tension-free closure. (t) Radiographic view immediately after implant placement with SynthoGraft in the spaces between the implant plateaus to eliminate any dead spaces. (u) Clinical image prior to uncovering the implant. (v) Radiographic view prior to uncovering the implant. (w) A no. 12 curved blade is used to make a precise incision that splits the thin attached gingiva up to the distal surface of the tooth. (x) A full-thickness flap is reflected, showing the healed bone graft completely covering the implant. (y) After removing a small amount of new bone, the black Healing Plug is retrieved from the well of the implant. (z) A gold 5.0-mm Sulcus Former attached to a green threaded knob is rotated on a guide pin seated in the well of the implant to shape the tissues to conform to the hemispheric base of the intended 5.0mm abutment. (aa) View of the final sulcus. (bb) Clinical view of a polyetheretherketone Healing Abutment helping to form the implant sulcus. (cc) Radiograph after the IAC was in function for 5 years. (dd) CBCT scan of grafted bone and restored implant 5 years after loading of the implant, revealing excellent buccal bone. (ee) Clinical view of IAC 5 years after being placed.

Treatment 3

The third presentation is of a 41-year-old man with a healthy medical history, who presented with bilaterally edentulous and atrophic mandibular molar alveolar ridges (Figs 19-17a to 19-17c). Rather than doing two-stage mandibular ridge-splitting procedures (see chapter 13), because of the success of 5.0- and 6.0-mm short implants, it was decided to simultaneously place two 4.0 × 6.0–mm implants bilaterally with a GBR procedure using SynthoGraft and a resorbable collagen membrane in a manner similar to the previous treatments. The radiographic images of the two implants placed in the posterior right mandible over a period of 28 months attest to the efficacy of this GBR treatment Fig 19-17 (a to c) Preoperative CBCT scans with intended implant placement in green . (d) Postoperative radiograph. (e) Five-month postoperative radiograph. (f) Radiograph with two Universal Abutments after implant uncovering. (g) Radiograph after IAC placement. (h) Radiograph 3 months after IAC placement. (i) Radiograph 28 months after IAC placement. (j and k) CBCT scans 28 months after IAC placement clearly show buccal bone over the grafted surface of the implants.

(Figs 19-17d to 19-17i). Further credence is given to this treatment (of only partially placing the implant’s buccal surface within an osteotomy and grafting the exposed implant shoulder and plateaus with SynthoGraft) by comparing the preoperative CBCT scan images with the 28-month postoperative CBCT scan images (Figs 19-17j and 19-17k).

GBR with Rigid Crib Support

Some surgical sites and their surrounding tissues may preclude the use of GBR with soft barrier membranes only; in these instances, a rigid crib or reinforced membrane is required to protect against soft tissue encroachment and movement of the graft. The following treatments describe the use of GBR with a rigid crib support of Ti-mesh. Fig 19-18 (a) Periapical radiograph shows bone defect in the region of the maxillary right premolar. (b) Appearance of the surgical site after removal of the fixed prosthesis. (c) Elevating a full-thickness flap reveals the healed oroantral fistula, which was subsequently dissected. (d) Removal of the fistula scar caused a small part of the periosteum attached to the sinus mucosal lining to tear. A residual buccal wall fenestration resulting from incomplete healing of the oroantral communication can be observed. (e) A Kerrison rongeur was introduced to widen the fenestration. (f) Freeing and mobilizing the sinus mucosal lining with blunt curettes. (g) Injecting SynthoGraft into the bone cavity. (h) Packing the graft with additional graft material to condense it within the bone cavity. —_Y

GBR with rigid crib support for a maxillary premolar

A 39-year-old woman presented with a failed lateral sinus elevation and subsequent oroantral fistula with concomitant sinusitis. The patient was treated with antibiotics until the sinusitis resolved, which subsequently allowed the fistula to close spontaneously. Initially, an implant was placed in the location of the maxillary right second molar while the soft tissues in the premolar region were allowed to fully heal and consolidate (Fig 19-18a). The GBR treatment would then be carried out in three phases: first, the sinus elevation procedure would be performed, followed by reconstruction of the alveolar crest; second, a Ti-mesh crib would be used to protect the crestal expansion both horizontally and vertically; third, the Ti-mesh would be removed, followed by the placement of implants.

To begin the procedure, the patient’s fixed partial denture spanning from the molar to the canine was removed (Fig 1918b), and a papilla-sparing incision was made. The full-thickness flap was raised, and the scar tissue resulting from the oroantral fistula was removed (Fig 19-18c). Removal of the scar tissue left a small part of the periosteum attached to the mucosal lining, along with a residual buccal wall fenestration caused by incomplete healing of the oroantral communication (Fig 19-18d).

A Kerrison rongeur was gently introduced into the fenestration with the blunt side mobilizing the mucosal lining, which allowed the fenestration to be widened without the need for rotary instruments (Fig 19-18e). Next, the sinus mucosal lining was freed and mobilized with blunt curettes (Fig 19-18f). A SynthoGraft mixture was then prepared and injected into the bone cavity with a 4.0-mm Bone-Graft Syringe (Fig 19-18g). The graft was then packed and condensed using curettes, followed by the addition of more graft material until the cavity created by the reflection of the sinus membrane was completely filled (Figs 19-18h). Once the sinus cavity was adequately filled with SynthoGraft, a resorbable collagen barrier membrane was applied and secured; the site was then closed with a 4.0 chromic gut suture and allowed to heal for 1 month (Figs 19-18i to 19-18k).

For the second phase of the procedure, a mucoperiosteal flap was made with a crestal incision, revealing the healthy appearance of the recently healed SynthoGraft mixture (Fig 19-18l). A piece of sterile paper was used to measure and design the Ti-mesh (Fig 19-18m). The paper was cut and tried repeatedly until it fit satisfactorily over the defect, and it was then used as a template with which to trim a 0.2-mm Ti-mesh (Fig 19-18n). The Ti-mesh was then bent to mimic the desired appearance of the crestal bone and tried at the surgical site to verify its fit (Figs 19-18o and 19-18p). After the fit of the Ti-mesh was shown to be acceptable, two tacks were used to secure the superior-most aspect of the buccal side of the mesh to the native bone (Fig 19-18q). Once the mesh was secured, it was folded back, and a collagen barrier membrane was trimmed and inserted beneath it, followed by the preparation and injection of SynthoGraft (Fig 19-18r). Subsequent to the SynthoGraft injection, the mesh was folded back over the crest, tucked beneath the palatal soft tissues, and held in place with a retention suture that began and terminated on the palatal surface (Fig 19-18s). A postoperative radiograph confirmed the filling of the vertical defect, and the site was allowed to heal for 3 months (Fig 19-18t). Fig 19-18 (cont) (i) Securing the graft with a resorbable collagen barrier membrane. (j) Closing the surgical site with 4.0 chromic gut suture. (k) Postoperative radiograph showing the result of SynthoGraft application. Note the containment of the graft in the sinus cavity. (l) During the second phase, a full-thickness flap was raised, revealing the healed SynthoGraft. The bone underlying the flap appeared healthy and shows good surface bleeding. (m) Using sterile paper as a basis for designing the Ti-mesh. (n) Once the paper satisfactorily covers the defect, a 0.2-mm Ti-mesh was trimmed to match the shape of the paper. (o) Bending the Ti-mesh to conform to the contour of the crestal bone. (p) Trying the Ti-mesh at the surgical site to verify its fit prior to being secured. (q) Two tacks were used to secure the buccal side of the mesh. (r) A 4.0-mm Bone-Graft Syringe was used to inject SynthoGraft under the mesh. (s) The Ti-mesh was folded back over the crest and tucked under the palatal soft tissues. (t) Postoperative radiograph depicting the vertical defect filled with graft material. (u) During the third phase, a full-thickness flap was raised to expose the Ti-mesh for its removal. (v) Appearance of newly formed bone after removal of the Ti-mesh. (w) Postoperative radiograph showing placement of implants in newly formed bone.

The third and final phase of the procedure was the removal of the Ti-mesh and placement of implants. After a 3-month healing period, a full-thickness flap was raised to expose the Ti-mesh (Fig 19-18u). The tacks securing the mesh were removed, followed by the mesh itself, revealing the newly formed bone at the location of the graft (Fig 19-18v). Implants were then placed as previously described; the postoperative radiographs demonstrate their stability in the newly formed bone (Fig 19-18w). Fig 19-19 (a) Preoperative appearance of the edentulous maxillary arch. (b) Preoperative panoramic radiograph showing atrophic maxilla. (c) The right maxillary alveolus was exposed, showing its atrophic, knife-edge appearance. (d) Pilot drill initiating osteotomy with external irrigation. (e) A 2.5-mm reamer was used to expand the osteotomy. Note the missing facial and palatal cortices down to approximately 8 mm. (f) Formation of a cleft defect caused by loss of bone at the cortical plates. (g) Completing the osteotomy with a 3.0-mm reamer. (h) Placing a 3.0 × 8.0–mm implant in the cleft defect. (i) Appearance of implant after being placed in the osteotomy. The extent of the crestal atrophy is made apparent by the exposure of the facial and palatal surfaces of the implant. —-

GBR with rigid crib support for a canine site in an edentulous maxilla

A 51-year-old woman presented for implant placements in her edentulous maxilla (Fig 19-19a). A course of treatment was planned, whereby the maxillary arch would be restored using a TRINIA prosthesis, requiring atrophic areas of the anterior maxilla to be expanded. However, the option of ridge splitting was not viable because of the lack of adequate cancellous bone between the two cortices, preventing the propagation of a split. Furthermore, with the mandibular arch occupied with a fixed, implant-supported restoration, plans to harvest cortical bone from the mandible were ruled out (Fig 19-19b). Because of the patient’s unique circumstances, implants were placed in the location of the maxillary canines that would be supported and stabilized by SynthoGraft with Ti-meshes.

First, a full-thickness flap was raised, exposing the extremely atrophic, knife-edge appearance of the patient’s alveolar crest (Fig 19-19c). An osteotomy was then initiated for the right area using a pilot drill with external irrigation (Fig 19-19d). To widen the osteotomy, a succession of reamers was used; however, due to the extreme atrophic and fragile nature of the crestal bone, both the facial and palatal cortices were lost down to a depth of approximately 8 mm, resulting in a cleft defect (Figs 19-19e to 19-19g). After reaming the osteotomy, the implant was placed, at which point the consequences of the cleft defect became quite apparent (Figs 19-19h and 19-19i). Both the facial and palatal surfaces of the implant were completely exposed. Fig 19-19 (cont) (j) The Ti-mesh was fit over the exposed surface and secured with two screws on its palatal surface. (k) SynthoGraft was injected over the exposed implant surfaces with a 4.0-mm Bone-Graft Syringe. (l) Additional SynthoGraft was injected to ensure an adequate amount of bone will be present to support the implant. (m) Screws were placed on the facial aspect of the mesh and graft for added stability. (n) Postoperative panoramic radiograph showing the placement of four implants.

To support the placement of a graft over the exposed portion of the implant, a Ti-mesh was trimmed and fitted over the implant and then secured with two screws on the palatal surface (Fig 19-19j). After the Ti-mesh was secured, it was folded back and a collagen barrier membrane was placed beneath it. Next, SynthoGraft was prepared and injected over the exposed implant surfaces and surrounding area to generate the needed thickness to support the implant (Figs 19-19k and 19-19l). To further secure the mesh and graft, additional screws were placed on the facial portion of the mesh (Fig 19-19m).

This technique was then repeated for the maxillary left canine, along with the placement of implants at the location of both maxillary molars (Fig 19-19n).

LPRF: An Alternative to Collagen Membranes

Leukocyte- and platelet-rich fibrin (LPRF) is a platelet concentrate obtained by centrifuging the patient’s blood, which consists of platelets and leukocytes within a fibrin clot.[52–54] LRPF is a potentially cost-effective adjunctive agent with a proven record for promoting enhanced soft tissue healing. The following treatments illustrate the use of LPRF with Bicon implants.

LPRF in maxillary left central incisor site

A 54-year-old man in good health presented with a fractured maxillary left central incisor. The fractured root tip was removed, and an implant was placed with its black Healing Plug (Fig 19-20a). Rather than placing a collagen plug, as shown in previous treatments, a concentrate of LPRF was prepared from the patient’s own blood and sutured in place over the implant (Figs 19-20b to 19-20d).

GBR with rigid crib support and LPRF: Maxillary canine

A 27-year-old woman in good health presented with a significant bone defect resulting from the surgical removal of her high, horizontally positioned and impacted maxillary right canine (Figs 19-21a to 19-21e). Initial treatment comprised the placement of a short 4.5 × 6.0–mm implant and a synthetic bone augmentation with a minimal amount of autologous bone from the osteotomy preparation within her three-wall defect, which was covered with a Ti-mesh crib and an LPRF membrane (Figs 19-21f to 19-21j).

Unlike the previously presented Ti-mesh treatments, only a minimal portion on the alveolar top of the mesh was removed 4 months later to uncover the implant without removing the entire mesh. After 7 months, with a Healing Abutment, a provi- Fig 19-20 (a) Clinical image of the black Healing Plug being inserted into an implant. (b and c) An LPRF concentrate was placed into the osteotomy to cover the implant. (d) A resorbable suture has been placed over the LPRF. Fig 19-21 (a and b) Clinical images showing significant bone defect at the site of the patient’s extracted maxillary right canine. (c and d) CBCT images showing significant bone defect at the site of the patient’s extracted maxillary right canine. (e) Preoperative digital image showing significant bone defect at the site of the patient’s extracted maxillary right canine. — sional crown was placed on an impression post (Figs 19-21k to 19-21m). The patient did not return to continue her treatment for almost 3 years, at the end of which time an implant-level transfer impression was made and an IAC was delivered.

Unfortunately, interference of the extremely narrow soft tissue sulcus prevented the initial complete seating of the

IAC (Fig 19-21n). However, after two minimal palatal relieving incisions, the IAC was definitively seated. The 4-year postoperative clinical and radiographic images attest to the meaningful quality of life benefits of this Bicon implant treatment (Figs 19-21o and 19-21p). Fig 19-21 (cont) (f) The seated implant with its black Healing Plug and Ti-mesh. (g) Harvested bone covering the implant and Ti-mesh. (h) Ti membrane covering the implant and harvested bone. (i) LPRF membrane covering Ti-mesh. (j) Postoperative radiograph of the implant and Ti-mesh. (k) Radiograph of impression post inserted into implant at the time of its uncovering, 7 months after placement. (l) CBCT images at the time of implant uncovering. (m) CBCT image almost 3 years after implant uncovering. (n) Radiograph of the incompletely seated IAC as indicated by the radiolucency below the post. (o and p) Clinical view and radiograph of the definitively seated IAC 4 years after implant placement.

Conclusion

The patient’s intrinsic bone regenerative abilities are a powerful ally for clinicians during the treatment of edentulism; even so, additional measures such as the use of β-TCP for socket regeneration, or guided bone regeneration, are sometimes necessary to produce superior outcomes. This chapter has shown several examples of how the use of β-TCP (ie, SynthoGraft) can successfully preserve the alveolar crest following tooth extraction and aid in the regeneration of bone in areas characterized by large bony defects. GBR procedures utilizing SynthoGraft are also an effective alternative to mandibular ridge splitting. By reviewing this chapter, any clinician considering the use of bone-grafting materials (especially β-TCP) for surgical procedures requiring bone regeneration should have a better understanding of the material’s background, techniques, and capabilities.

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Conclusion

Vincent J. Morgan

Hopefully, this text has encouraged you to think differently and independently from conventional precepts in dentistry. It is important to remain true to lessons learned in school or in formal training, but that does not replace the importance of questioning the uncontested or challenging the norm. Many creative ideas often appear to be counterintuitive; however, swimming against the tide of institutional thought can often lead to better and more logical solutions.

Consider the logic of the concepts, products, and techniques presented in this book. Slow-speed drilling, which has been a feature of the Bicon system since 1985, is a concept that has many advantages over the ubiquitous practice of high-speed drilling with irrigation. Is it logical to choose a drilling system that heats bone when slow drilling without generating heat is an option? The common practice of using irrigation while drilling decreases the operator’s visibility, occupies the assistant with suctioning a patient’s mouth awash with irrigating solution, and most importantly, washes away the patient’s blood, which is essential to the bodily healing mechanism. Slow-speed drilling without irrigation avoids all of these disadvantages that are inherent with high-speed drilling.

It may seem natural to think that longer implants provide better stability, but the proven reality is that shorter implants are better and can additionally avoid surgical risks and grafting procedures. Plateaus or fins provide healing chambers for faster osseointegration by producing Haversian or cortical-like bone with mechanical properties superior to the appositional bone that forms around threaded implants. The Bicon implant’s sloping shoulder provides space for the growth of not only aesthetic interdental papillae but also for the bone needed to support these healthy papillae. Designs without a sloping shoulder provide neither. A bacterially sealed, locking-taper implant-abutment interface (IAI) without micromovement not only prevents a septic flux that could lead to peri-implantitis but also fosters bone gain and permits the positioning of the IAI below the crest of bone. Subcrestal implant placements allow for the use of dental implants in adolescents, as well as more natural-looking emergence profiles for restorations. A round abutment shaft with 360 degrees of universal positioning eliminates indexing and provides for the extraoral cementation of crowns (which eliminates the deleterious effects of extraneous cement), as well as for Bicon’s cementless and screwless Integrated Abutment Crown and for the orientation and seating of multiple abutments with a prosthesis even with nonparallel implants. This also facilitates the use of TRINIA, a fiber-reinforced computer-aided design/computer-assisted manufacturing resin material with unmatched clinical capabilities, including the use of telescopic restorations with prefabricated retentive copings. Finally, the use of SynthoGraft, a pure-phase beta-tricalcium phosphate synthetic grafting material with porous particles, eliminates the inherent risks associated with nonsynthetic materials. As mentioned in chapter 19, the current concept of universally recommending prophylactic socket preservation treatments should be critically examined as to whether it is a logical and efficacious treatment, and if it is prudent to use xenografts when there are alternative materials.

In the preface to this book, we mentioned the metaphor used by Patrick Schmidlin, a professor in Zurich, to describe his perception of Bicon’s viability as a fish swimming upstream. His metaphor may conjure imagery of an intense and lonely struggle, which in some ways rings true. Although much of our success is owed to doing things our own way over the years, Bicon has also benefitted from some unique advantages not afforded to other implant designs. The most important advantage is that Thomas Driskell got it right from the very outset. The Bicon design and its basic techniques have remained unchanged with over 32 years of consistency as of this publication. Is that not the hallmark of a truly timeless design? In contrast, other implant systems have changed dramatically, with some of them going through more than a dozen designs over the years. However, if you had purchased one of the first Bicon (DB Precision) surgical kits in 1985, you could use that very same kit and instrumentation to place a Bicon implant purchased today. Can that be said about any other implant system on the market?

To this date, our 32-year journey of design changes has primarily been a journey of providing scientifically based and clinically proven refinements and enhancements. The Bicon design has remained true to its principles, only being honed over the decades with some revolutionary surgical and restorative innovations. Bicon implants may soon become shorter still by employing the same fundamental principles of their time-proven design—a design that did not have to be reinvented just to support new marketing campaigns. While remaining true to its original design concepts, Bicon has been a font of creative improvements; for example, we are currently evaluating a novel approach of using only three short implants to support full-arch TRINIA telescopic restorations for both maxillary and mandibular atrophic alveolar arches.

One can now see other implant companies offering shorter implants, sloping shoulders, deep fins or plateaus, and slow-speed drilling—design features initially unique to Bicon that were almost universally eschewed and dismissed at the time of their introduction by those considered the erudite leaders in our profession. Now, as these features are accepted and adopted, you can see the currents shifting in Bicon’s direction. That begs the question, did that little fish swimming upstream change the course of a great river? Perhaps we will know the answer in another 30 years or so. In the meantime, we’ll keep swimming.

Index

Page numbers followed by “f” indicate figures; those followed by “t” indicate tables; those followed by “b” indicate boxes

A

• Abutment(s) crown cementation to, 21 definition of, 49 evolution of, 17–19, 18f

• hemispheric base of, 12–14, 13f, 246–247, 247f

• implant interface with. See Implantabutment interface; Locking-taper implant-abutment interface; Tapered integrated screw implant-abutment interface.

loosening of, 28, 233 polyetheretherketone, 221, 222f Sinus Lift, 279, 283, 283f 360 degrees of positioning for, 12, 13f, 28, 116, 123, 148

titanium. See Titanium abutment. universal. See Universal Abutment. Adjuvant therapy, 265 Adolescents atrophic maxillary ridge in, 211–212, 212f–213f

Bicon implants in advantages of, 116 capabilities of, 116–117 concerning regarding, 116 indications for, 115 long-term studies of, 116 placement of, 15, 16f treatments, 117f–121f, 117–121 definition of, 115 facial growth in, 115 implant-abutment interface in, 116 skeletal growth in, 115

Allen, Charles, 3 Allografts, 288 Alloplasts, 288–289 Alveolar crest height of, augmentation options based on, 152f, 152t mandibular, 182 maxillary, 182 nonsteroidal anti-inflammatory drugs effect on growth of, 248f–250f, 248–250

stability of, 233 Alveolar process, 181 Alveolar ridge augmentation. See also Bone augmentation. distraction osteogenesis for, 217, 217f overview of, 181 ridge splitting techniques for. See Ridge splitting.

screw-retained cortical graft technique for, 196–197, 197f al-Zahrawi, Abu al-Qasim, 3 Ameloblastoma, 253–255, 254f–256f Angiogenesis, 39f, 39–40

Angled abutments, 138f Anodontia, 115 Anterior implant placement aesthetic soft tissue, 111–113, 112f angulation, 104–105 delayed-immediate approach, 107 immediate, 106 mandibular central incisors, 107–108, 110, 110f guidelines for, 105t lateral incisors, 107–108 maxillary canines, 107 central incisors, 107 description of, 99f, 100 guidelines for, 105t lateral incisors, 107 treatments, 108–110, 109f–110f positioning for, 104–105 recommendations for, 104–107 surgical procedures for, 104, 104f, 105t treatments, 108–113, 109f–112f Anterior mandible, 103 Anterior maxilla, 103 Anterior restorations, 108 Appositional bone, 26 Atrophic mandibular ridge bone augmentation procedures for classification of, 216, 216f overview of, 215–217 pedicled sandwich plasty, 217f–219f, 217–219 TRINIA prosthesis, 219–223, 220f–223f, 227–228, 228f distraction osteogenesis for, 217, 217f narrow implants in, 16f short implants for, 218–219 without augmentation, 223f–228f, 223–228 Atrophic maxillary ridge in adolescents, 211–212, 212f–213f Bicon short implants for, 202f–205f, 202– 203, 205, 212, 212f in bone marrow transplantation patient, 259, 260f in diabetes mellitus patient, 259f in epidermolysis bullosa patient, 256f–258f, 256–258

horseshoe Le Fort I osteotomy for, 200f, 200–201 lateral sinus lift for, 200 maxillary tuberosity implants, 204–212, 205f–213f narrow implants in, 16f treatments, 205f–213f, 205–212 TRINIA prosthesis for, 202f–204f,

202–203, 206, 207f, 209f, 209–211, 211f–213f in type II diabetes mellitus patient, 259f zygomatic implants for, 201f–202f, 201– 202, 204f Atrophy

Cawood and Howell classification of, 199, 200f, 204 mandibular ridge. See Atrophic mandibular ridge.

maxillary ridge. See Atrophic maxillary ridge. Autografts, 288 Autologous bone, 290

B

Bacteria implant surface effects on colonization of, 51

leakage of, in implant-abutment interface microgaps and micropumps, 50–51, 65–68, 66f, 66t–67t in mouth, 64–65, 65t Bacterial seal description of, 12, 50 at implant-abutment interface, 68, 68f, 73, 87, 116

Basic multicellular units, 41f, 42, 57 Benign sinus lesion, lateral sinus lift for, 176, 177b, 177f–179f Bicon implant(s)

abutment and, interface between. See Implant-abutment interface.

in adolescents. See Adolescents. advantages of, 116 bone healing around, 26 bone remodeling around, 45, 45f, 59, 59f bony foundation of, 26 diameter of, 15f features of, 10, 11f, 219 history of, 6–10 indications for, 14, 17 restorative capabilities of, 19f–23f, 19–23 short implants. See Short implants. size of, 86, 86f subcrestal placement of, 87, 87f, 318 survival rates for, 75–76, 76t threaded implants versus, 279, 284 treatments, 76–83, 77f–83f

Bicon implant design bacterial seal, 12, 50, 116 description of, 123–124 hemispheric base, 12–14, 13f, 124, 148 narrow width, 15, 16f peri-implant bone gain, 16f, 17 plateau-root form. See Plateau-root form implant. plateaued and tapered body, 11, 11f, 26 science of, 9–10 short length, 14–15, 15f sloping shoulder, 11f–12f, 11–12, 15, 284, 317 slow drilling, 14, 14f, 85, 317

Index

360 degrees of abutment positioning, 12, 13f, 28, 116, 123, 148

Bicon implant placement advantages of, 279 calcium phosphate coating with, 245 in compromised tissue. See Compromised tissue.

guided surgery procedure for, 98–99, 99f–100f, 100b hydroxyapatite coatings with, 245, 245f immediately loaded, 96f–97f, 96–98, 97b instruments/tools for, 88b, 125 in mandible, 101, 101f in maxilla, 100–101, 101b, 101f quick-reference guides for, 88, 95b, 97b recommended technique for, 85 single-stage procedure, 95, 95b subcrestal, 87, 87f, 318 surgical templates for, 87–88, 88f–89f two-stage procedure abutment placement, 93–94, 94f bone harvesting during reaming, 91, 91f–92f implant placement, 92, 92f implant uncovering, 92–93, 93f osteotomy, 90, 90f papillae-sparing flap used in, 89f pilot drill depth, 90, 90f quick-reference guide for, 95b reamers used in, 90–92, 91f removal of healing plug, 92f, 93 site preparation, 88, 89f–91f, 90–92 temporization sleeve, 94f, 94–96

Bicon Implant System, 10, 123 Bidirectional leakage tests, for bacterial leakage, 68f–69f, 68–69 Bilateral cleft palate, 262–264, 264f Bioceramics, 288 Biofilm, 64 Biologic response angiogenesis, 39f, 39–40 inflammatory response, 39–40 osteoblast activation, 41 platelet activation, 39f–40f, 39–40 protein adsorption, 38f, 38–39 stem cell recruitment, 41 vascularization, 40, 40f Bisphosphonate therapy, 262, 263f Bite force, 29, 29t Black, G. V., 277 Black healing plug, 92f, 93 BMPs. See Bone morphogenetic proteins. Bobbio, Amadeo, 2 Bone irradiated, 269–274, 270f–274f low-density, 279 morphology of, implant macrogeometry effects on, 44–45 Bone augmentation, for atrophic mandibular ridge classification of, 216, 216f overview of, 215–217 pedicled sandwich plasty, 217f–219f, 217–219 TRINIA prosthesis, 219–223, 220f–223f Bone cysts, 277 Bone gain factors associated with, 239, 239t hemispheric base’s role in, 13, 13f mandibular, 237, 237f maxillary, 234f–237f, 234–236 peri-implant, 16f, 17 Bone healing around screw-root form implants, 43f, 43–44 description of, 26 interfacial, 43f, 43–44 intramembranous-like, 43f, 44 Bone loss, peri-implant description of, 234, 239, 240t, 250f with short implants, 232 Bone marrow transplantation, 258–259, 260f Bone modeling definition of, 215 illustration of, 10f minimum effective strain for, 248 Bone morphogenetic proteins BMP-2, 40f, 41 description of, 41 Bone quality, 86f, 86–87 Bone regeneration bone-grafting materials, 288–289 guided. See Guided bone regeneration. implant macrogeometry effects on, 41–45, 43f–44f macrophage’s role in, 40 osteoblast extracellular matrix deposition in, 41f, 42 osteoclastogenesis in, 42, 43f osteoconduction, 287 osteogenesis in, 41f, 42, 287 osteoinduction, 287 processes involved in, 287 socket. See Socket regeneration. summary of, 314 ß-tricalcium phosphate for, 288–289, 289f, 314 Bone remodeling around Bicon implants, 59, 59f around plateau-root form implants, 45, 45f around screw-root form implants, 44–45 description of, 215 illustration of, 10f implant macrogeometry effects on, 57–59 implant survivability affected by, 51 interfacial, 43f, 43–44 intramembranous-like, 43f Bone resorption osteoclasts in, 42 Wolff’s studies of, 199 Bone sialoprotein, 38, 41f Bone voids computed tomography of, 278, 278f histology of, 278–279 implant design’s role in recognition of, 279 management of, 279–284, 280f–284f osteotomy detection of, 279, 281–282, 282f, 284 overview of, 277–278 radiographs of, 278, 278f shape of, 280, 280f SynthoGraft for, 280, 280f treatments, 281f–284f, 281–284 Bone-grafting materials for internal sinus lift, 155, 155f types of, 288–289 Bone-loading platform switching, 247

Bonwill, W. G. A., 3 Brånemark, Per-Ingvar, 6 Brevis Abutment, 18, 18f Bruxism, 232, 232f BSP. See Bone sialoprotein. Buccal plate, 107

C

CAD/CAM fixed prosthetics created with, 23, 23f polyceramic crowns, 129f zirconia copings, 137f Calcium phosphate for bone grafting, 288 coating of, 244f–246f, 244–246 Camouflage techniques, 113 Canaliculi, 42, 43f Canines guided bone regeneration with rigid crib support for, 311f–312f, 311–312 mandibular, 108 maxillary, 107, 300–301, 301f Case studies. See Treatment(s). Cast chrome-cobalt bar, implant-retained denture on, 140f Cawood and Howell atrophy classification, 199, 200f, 204 Cementation, extraoral, 21 Cement-retained prostheses, 30 Cerasorb, 289 Chemokines, 39 CIR. See Crown-to-implant ratio. Cleft palate, bilateral, 262–264, 264f Commercially pure titanium, 26 Complications description of, 25 increased crown-to-implant ratio as cause of, 233 Composite abutment base, 246, 247f Compromised tissue ameloblastoma, 253–255, 254f–256f bisphosphonate therapy, 262, 263f bone marrow transplantation, 258–259, 260f cleft palate, 262–264, 264f denosumab therapy, 261f–262f, 261–262 diabetes mellitus, 258, 259f epidermolysis bullosa, 256f–258f, 256–258 hematopoietic stem cell transplantation, 258–259, 260f irradiated bone, 269–274, 270f–274f mandibular squamous cell carcinoma, 265f–269f, 265–269 type II diabetes mellitus, 258, 259f Contact osteogenesis, 42 Cortical-like Haversian bone, 11 Crestal bone. See Alveolar crest. Crestal osteotomy, 152 Crestal window sinus lift indications for, 161 internal sinus lift hybrid procedure, 158–161, 159f–161f overview of, 162 postoperative radiographs, 165, 165f procedure for, 162–165, 163f–165f quick guide for, 162, 162b SynthoGraft for, 163, 164f, 167, 169f titanium-mesh procedure with, 165–168, 166b, 167f–170f

Crown-alignment device, 125 Crown-to-implant ratio description of, 15, 26 increased, 233–234 reverse, 231–232 short implant effects on, 232–233 Crown-to-root ratio (CRR) description of, 231 normal, 231 Cytokines, 39–40

D

DB Bioengineering, 7 DB Precision Fin Implant, 7–9, 8f, 318 Delayed implant placement, 290, 291t Delayed-immediate approach for anterior implant placement, 107 guided bone regeneration with, 291

Denosumab therapy, 261f–262f, 261–262 Dental implant system definition of, 49 implant-abutment interface effects on, 52. See also Implant-abutment interface. load transfer on, 57

Diabetes mellitus, 258, 259f Die back, of bone, 26 DIONJ. See Drug-induced osteonecrosis of the jaw. Distance osteogenesis, 41f, 42 Distraction osteogenesis, 217, 217f Dolder bar, implant-retained denture on, 138f–139f Driskell, Thomas, 6–7, 9, 11, 56–57, 318 Drug-induced osteonecrosis of the jaw, 261f–263f, 261–262

E

Edmunds, J. M., 3 Effective length, 248, 248f Epidermolysis bullosa, 256f–258f, 256–258 Excessive loading, 238, 238f Extracellular matrix, 41f, 42

F

FEM. See Finite element method. Fibronectin, 38–39 Finite element method, 52, 57 Finned implant, 6 Fixed partial dentures cemented, 30 insertion of, 21, 22f TRINIA, 141f zirconia-veneered, 31 Fixed prosthesis CAD/CAM, 23, 23f definition of, 49 Fixed-detachable abutments, 18, 18f, 138f Four-unit TRINIA fixed partial denture, 141f Fresh frozen bone, 288 Full-thickness flap, ridge splitting with, 182– 183, 183f–186f

G

GBR. See Guided bone regeneration. Gingival esthetics, 16f

Gingivitis, 70 Gold standard, 32, 32f Gothic arch tracing, 148–150, 149f Greenfield, E. J., 3–5, 4f Greenfield Basket, 3–5, 4f Guided bone regeneration definition of, 290 with delayed-immediate approach, 291 description of, 279 in mandibular lateral incisor site, 302–303, 303f in mandibular molar sites, 303–308, 304f–308f in maxillary canine site, 300–301, 301f in maxillary lateral incisor site, 296, 297f–298f in maxillary premolar site, 299–302, 300f–302f with rigid crib support for canine site in edentulous maxilla, 311f–312f, 311–312 description of, 308

leukocyte- and plasma-rich fibrin with, 312–313, 313f–314f for maxillary premolars, 309f–310f, 309–310 SynthoGraft applications in, 309, 309f–310f, 314 Guided surgery, 98–99, 99f–100f, 100b

H

Hand reamers, 90–91, 91f, 162 Harris, S. M., 3 Healing chambers, 26, 43–44, 57 Hematopoietic stem cell transplantation, 258–259, 260f Hemispheric base, 12–14, 13f, 124, 246– 247, 247f

Horseshoe Le Fort I osteotomy, for atrophic maxillary ridge, 200f, 200–201 Hybrids, 140 Hydroxyapatite coating, 244f–246f, 244–246 Hypertrophic sinus, 167f

I

IACs. See Integrated Abutment Crowns. IAI. See Implant-abutment interface. Immature bone, 42

Immediate implant placement, 290, 291t, 295, 295f

Immediately loaded technique, for Bicon implant placement in anterior region, 106 description of, 96f–97f, 96–98, 97b

Implant(s). See also Bicon implant(s). ancient origins of, 1–2, 2f definition of, 49 design of, 5f, 5–7, 7f early attempts with, 3, 3f effective length of, 248, 248f history of, 1–8 length and width of, 247–248 long. See Long implants. screw-root form. See Screw-root form implants. short. See Short implants. surface area of, 248

Implant macrogeometry

bone morphology affected by, 44–45 bone regeneration affected by, 41–45, 43f–44f definition of, 56 load transfer affected by, 57 peri-implant bone remodeling affected by, 57–59

plateau-root form implant, 56–59 screw-root form implants. See Screw root form implants. Implant placement anterior. See Anterior implant placement. Bicon. See Bicon implant placement. delayed, 290, 291t ideal, 17 immediate, 290, 291t, 295, 295f subcrestal, 87, 87f, 318 Implant stability dip, 43 Implant surface bacterial colonization affected by, 51 fibronectin on, 38–39 protein changes induced by, 38 Implant-abutment interface in adolescents, 116 bacterial leakage at, 50–51, 59, 66t–67t, 68–70

bacterial seal at, 68, 68f, 73, 87, 116 characteristics of, 28t, 28–29 definition of, 49, 63, 116 description of, 123 designs for, 27–29, 28t, 49, 50f, 63–64, 64f locking-taper. See Locking-taper implantabutment interface.

microbial leakage at, 50–51, 59, 66t–67t microgaps and micropumps at, 51, 65–68, 66f

Morse taper, 27, 49, 50f peri-implant bone stress affected by, 51–52, 232

screw-in, 12, 64, 64f screw-retained, 27, 28t, 49, 50f, 64, 64f summary of, 28t, 28–29 tapered integrated screw. See Tapered integrated screw implant-abutment interface.

Implantology future of, 8 Greenfield’s contributions to, 3–5, 4f in Industrial Age, 3, 3f modern era of, 5–6

Implant-retained dentures attachment of, 138 on cast chrome-cobalt bar, 140f on Dolder bar, 138f–139f Incisive foramen, 107 Industrial Age, 3, 3f Inferior alveolar nerve, 101, 101f Inflammatory response, 39–40 Insertion force, 54f, 54–55, 59 Inside-out experiments, 67 Integrated Abutment Crowns in adolescents, 118, 118f buccolingual section of, 33f chairside modifications of, 124 description of, 116, 318 fabrication of, 20–21, 124 full arch of, 135f

Index

illustration of, 20f–21f, 124f

interproximal or occlusal contact closure using, 21, 22f maintenance of, 23 for mandibular lateral incisor restoration, 30f, 303 maxillary, 133f–134f for maxillary anterior implant, 108–110, 109f–110f, 236, 236f–237f for maxillary anterior restorations, 108 metal margin concealment with, 21, 21f, 136f prosthetic posts used with, 20, 20f ridge-lap, 121, 121f single mandibular, 130f–131f single maxillary, 132f treatments, 183, 186f, 236, 236f–237f, 249, 249f–250f, 303f, 313, 314f Interfacial bone remodeling, 43f, 43–44 Internal conical connection, 27 Internal sinus lift calcium phosphate coating with, 245–246 crestal window hybrid procedure, 158– 161, 159f–161f goal of, 153 hydroxyapatite coating with, 245–246, 246f implant insertion and seating, 156, 157f presurgical analysis and planning for, 152–153, 153f procedure for, 154–157, 155f–157f quick guide for, 154b radiographic assessments before, 153f, 153–154 SynthoGraft used in, 155f, 155–156, 159, 161, 246 Interproximal contacts, 21, 22f Intramedullary cavities, 277 Intramembranous-like bone remodeling, 43f, 44 Iridium-platinum alloy, 5 Irradiated bone, 269–274, 270f–274f Irrigation, 85

K

Khoury saw, 218 Khoury trephine technique, 262

L

Lacunae, 42 Lamellar bone, 26 Latch reamers, 90–92, 91f, 106 Lateral antrostomy, 152 Lateral sinus lift atrophic maxillary ridge treated with, 200 benign sinus lesion managed with, 176, 177b, 177f–179f description of, 151, 170 pedicled periosteal flap used in, 175, 175f postoperative radiograph of, 176f procedure for, 171f–176f, 171–176 quick guide for, 171f radiographic assessments before, 171, 171f–172f SynthoGraft for, 172 Le Fort I osteotomy, horseshoe, 200f, 200–201

Leukocyte- and plasma-rich fibrin, 312–313, 313f–314f

Leukocyte- and platelet-rich fibrin plug, 106 Leventhal, Gottlieb S., 5 Linkow, Leonard, 6, 7f Load transfer, 57 Load-bearing, 247 Loading, excessive, 238, 238f Locking-taper implant-abutment interface. See also Morse taper. bacterial leakage at, 67t bacterial seal created by, 12, 50, 87 benefits of, 12, 21, 30, 148, 317–318 characteristics of, 28t definition of, 50 description of, 104 design of, 64f engaging of, 94, 94f Integrated Abutment Crown in, 124 microgap prevention using, 68 milled prosthesis bonding to, 30 screw-retained implant-abutment interface versus, 27 tapered integrated screw implantabutment interface versus, 27 360 degrees of abutment positioning with, 12, 13f, 28, 116, 123, 148 Long implants bone remodeling around, 59, 59f case study of, 82, 83f strain distribution with, 58 survival rate of, 82, 83f Loosening torque, 54f–55f, 54–55 Low-density bone, 279

M

Macrophages, 39–40 Maggiolo’s implant, 3, 3f Mandible alveolar crest, 182 anterior, 103 Bicon implants in placement of, 101–102, 101f selection of, 86, 86f bone gain in, 237, 237f Mandibular first molar case study of, 76, 77f implant restoration of, 248f Mandibular full-arch screw-retained TRINIA restoration, 142f Mandibular full-arch telescopic prostheses, 147f–148f, 147–148 Mandibular incisors central, socket regeneration of, 292–293, 293f–294f extraction and immediate implant placement of, 110, 110f fracture of, 120f lateral, guided bone regeneration for, 302–303, 303f right, case study of, 81, 81f Mandibular molars, guided bone regeneration for, 303–308, 304f–308f Mandibular nerve, 82, 83f Mandibular premolars, 102 Mandibular ridge atrophic. See Atrophic mandibular ridge.

splitting of guided bone regeneration application to, 303 with split-thickness flap, 195f–196f, 195–196

with two-stage window technique, 186–190, 187f–190f Mandibular squamous cell carcinoma, 265f–269f, 265–269 Matrix metalloproteinases, 40 Maxilla alveolar crest, 182 anterior, 103 anterior implants in jig for seating of, 99f, 100 poorly positioned, restoration of, 126, 126f Bicon implants in placement of, 100–101, 101b, 101f selection of, 86, 86f bone gain in, 234f–237f, 234–236 edentulous, guided bone regeneration with rigid crib support for canine site in, 311f–312f, 311–312 posterior, 82 Maxillary canines, guided bone regeneration for, 300–301, 301f Maxillary first molar extraction of, 234f implant restoration of, 234f–235f treatments, 76, 77f, 82, 82f Maxillary full-arch telescopic prostheses, 147f–148f, 147–148 Maxillary incisors central Bicon implants for, 100, 107 case study of, 78f–79f, 78–79 endodontically treated, 112f leukocyte- and plasma-rich fibrin application for, 312, 313f socket regeneration of, 291f–293f, 291–292 immediately loaded implants for, 96f–98f, 96, 107 lateral Bicon implants for, 107 case study of, 79, 80f congenitally missing, 117f guided bone regeneration for, 296, 297f–298f zirconia crowns, 128f Maxillary Integrated Abutment Crowns, 133f–134f Maxillary premolars, guided bone regeneration for description of, 299–302, 300f–302f with rigid crib support, 309f–310f, 309–310

Maxillary ridge atrophic. See Atrophic maxillary ridge. splitting of with full-thickness flap, 182–183, 183f–186f with split-thickness flap, 191–196, 192f–195f

Maxillary right sinus carcinoma, 274, 274f Maxillary second molar, 76, 77f Maxillary tuberosity implants, 204–212, 205f–213f Maya mandible, 1–3

Mesenchymal stem cells, 40f, 41 Metal ceramics long-term studies of, 30, 31f strength of, 32 Metal margin concealment, Integrated Abutment Crowns for, 21, 21f, 136f Methyl methacrylate, 125 Microbial leakage, at implant-abutment interface, 50–51, 59 Microbiota, 64–65 MicroCT scanning, 69–70 Microgaps, 51, 65–68, 66f Micropumps, 51, 65, 67–68 Milled telescopic copings, 144, 145f Minimum effective strain, for bone modeling, 248 Modulus of elasticity, 32, 32f, 32t Morse taper bacterial leakage with, 51, 67t components of, 64 description of, 27, 49 design of, 63–64, 64f illustration of, 50f load carrying and transfer characteristics enabled by, 51

locking-taper implant-abutment interface as. See Locking-taper implantabutment interface.

Mouth microbiota, 64–65 Multiphasic material, 140 Mylohyoid line, 101, 101f

N

Narrow-diameter implants, 52 Neoadjuvant therapy, 265 Non-Shouldered Abutment, 18, 18f Nonsteroidal anti-inflammatory drugs, 248f–250f, 248–250 Nonverbal communication, 103 NSAIDs. See Nonsteroidal anti-inflammatory drugs.

O

Occlusal contacts, 21, 22f Occlusal forces, 11, 11f Occlusal load transfer, 57 OPN. See Osteopontin. Oral squamous cell carcinoma, 265f–269f, 265–269 Osseointegration ancient examples of, 2, 2f Brånemark’s contributions to, 6 definition of, 37 factors that affect, 26 intramembranous-like healing during, 44, 44f Osteoblasts activation of, 41 in bone remodeling, 215 extracellular matrix deposition by, 41f, 42 illustration of, 41f progenitors of, 40, 40f radiotherapy effects on, 269 Osteoclastogenesis, 42, 43f Osteoclasts, 41f, 42, 43f, 215 Osteoconduction, 287 Osteoconductivity, 287 Osteocutaneous fibula, 272f

Osteocytes, 41f, 42 Osteogenesis description of, 41f, 42 distraction, 217, 217f Osteoinduction, 287 Osteonecrosis of the jaw, drug-induced, 261f–263f, 261–262 Osteopontin, 38, 41f, 42 Osteoprotegerin, 42 Osteoradionecrosis, 270 Osteotomy bone void recognition during, 279, 281– 282, 282f, 284

in immediately loaded surgical procedure, 96f, 97 implant macrogeometry and, 42, 43f pilot drill for, 17, 17f in two-stage surgical procedure, 90, 90f Osterix, 41 Outside-in experiments, 67

P

Palatal surgical template, 88, 89f Papillae-sparing flap, 89f Paralleling pins, 104f, 108 Pare, Ambrose, 3 Partial dentures intraoral bonding of, 21 TRINIA, 144 Payne, R. E., 3 Pedicled sandwich plasty, 217f–219f, 217–219 Periapical radiolucencies, 297f, 302f Peri-implant bone changes in, factors associated with, 240t–243t gain of, 16f, 17 hydroxyapatite coating effects on, 244f, 244–246 loss of, 234, 239, 240t, 250f stress on, 51–52, 232 Peri-implant disease mucositis, 65, 70 pathology that cause, 64–65, 65t peri-implantitis, 64–65, 71f, 232, 270 prevalence of, 70 treatment of, 70–73, 71f–72f treatments, 71f–72f, 71–73 Peri-implant inflammation, 72f, 72–73 Peri-implant microenvironment, 40, 40f Peri-implant wound healing angiogenesis, 39f, 39–40 inflammatory response, 39–40 osteoblast activation, 41 platelet activation, 39f–40f, 39–40 protein adsorption, 38f, 38–39 stem cell recruitment, 41 vascular endothelial growth factor in, 40 Peri-implantitis, 64–65, 71f, 232, 270 Periodontal ligament, 231, 294f Periotome, 294f Petechial bleeding, 13, 13f Peter, H. J., 4 Pilot drill description of, 17, 17f in two-stage surgical procedure, 90, 90f Plateau design, 11, 11f, 26, 317 Plateau-root form implant. See also Bicon implant(s).

bone remodeling around, 45, 45f description of, 6, 10 design of, 56, 56f development of, 56–57 healing chambers with, 26, 43–44, 57 intramembranous-like healing of, 44, 44f macrogeometry of, 56–59 stress and strain distributions with, 57–59, 58f

Platelet activation, 39f–40f, 39–40 Platelet-derived growth factor, 39 Platelet-rich fibrin, 263, 264f Platform switching, 11 Polyceramic crowns, 129f Polyetheretherketone, 112 Pontics, intraoral bonding of, 21 Popenoe, Dorothy, 1–2 Popenoe, Wilson, 1–2 Porcelain, 31, 31t Porcelain-fused-to-metal restorations, 20, 127f–128f, 255f, 264f Porcelain/ceramic material, 29 Posterior maxilla, implant placement in, 82, 83f Posterior restorations, 14, 15f Prefabricated titanium copings, for telescopic TRINIA prosthetics, 19, 19f Premolars mandibular, 102 maxillary. See Maxillary premolars. PRF implant. See Plateau-root form implant. Prostaglandins, 248 Prosthetic posts Integrated Abutment Crowns with, 20, 20f minimal-size, 23 Protein adsorption, 38f, 38–39 Provisional stabilizing prosthesis, 97f, 96–98 Pull-out force, 53f, 53–55, 54t, 59

R

RANKL, 42 Reamers, 90, 91f Removable prosthesis, 49 Removable restorations, 138 Resin seating jig, 146 Resin-matrix ceramics, 29 Resorbable collagen plug, 189, 190f Restorations. See also specific restoration. crowns, 125–137, 126f–137f description of, 124–125 porcelain fused to metal, 20, 127f–128f single mandibular Integrated Abutment Crown, 130f–131f single maxillary Integrated Abutment Crowns, 132f TRINIA. See TRINIA prostheses. Restorative materials for Bicon system, 29f, 29–32, 31f, 124 ceramics, 29–30 description of, 17 location considerations for, 30 long-term performance of, 26 metal ceramics, 30, 31f modulus of elasticity for, 32, 32f, 32t porcelain, 31, 31t types of, 26 zirconia, 30–31, 31t Reverse crown-to-implant ratio, 231–232

Ridge splitting with full-thickness flap, 182–183, 183f–186f guided bone regeneration application to, 303 mandibular alveolar crest, 182 maxillary alveolar crest, 182 prerequisites for, 182 with split-thickness flap, 191–196, 192f–196f with two-stage window technique, 186– 190, 187f–190f

Ridge-lap Integrated Abutment Crown, 121, 121f Rio Ulúa, 1–2 Runx2, 41

S

Saddle deformities, 181

SALSA. See Subantroscopic laterobasal sinus floor augmentation. Schneiderian membrane, 152–153, 161f, 200 Scholl, C. R., 3

Screw-root form implants bone healing around, 43f, 43–44 bone regeneration around, 43 bone remodeling around, 44–45 bone resorption with, 43f description of, 6 interfacial remodeling of, 43f, 43–44 RANKL activity in, 42 torquing of, 26, 43

Screw-in implant-abutment interface, 12, 64, 64f

Screw-retained cortical graft technique, 196–197, 197f

Screw-retained implant-abutment interface, 27, 28t, 49, 50f, 64, 64f

Screw-retained prostheses, 30 Seating jig fabrication of, 125

for maxillary anterior implants, 99f, 100 Self-releasing tapers, 49 Self-tapping vent-plant implants, 6, 7f Semicone angle, 49–50, 52 Shepherd bur, 178f Short implants arguments against using, 233 atrophic mandibular ridge treated with, 218–219

atrophic maxillary ridge treated with, 202f–205f, 202–203, 205, 212, 212f benefits of, 14–15, 15f bone gain or loss with, 232–233. See also Bone gain; Bone loss, peri-implant. bone remodeling around, 59, 59f case study of, 82, 83f crown-to-implant ratio affected by, 232–233 definition of, 103 excessive loading effects, 238, 238f recommendations for, 86, 86f strain distribution with, 58 survival rate of, 75–76, 76t, 82, 83f versatility of, 15f wide-diameter, 52

Signaling molecules, 39 Single mandibular Integrated Abutment Crown, 130f–131f

Single maxillary Integrated Abutment Crowns, 132f Single-implant restorations, bone levels around, 238f, 238–239, 239t–244t Sinus elevation. See Sinus lift. Sinus floor augmentation. See Sinus lift. Sinus lesion, lateral sinus lift for, 176, 177b, 177f–179f Sinus lift alveolar crest height and, 152f, 152t background on, 152 contraindications for, 152 crestal window indications for, 161 internal sinus lift hybrid procedure, 158–161, 159f–161f overview of, 162 postoperative radiographs, 165, 165f procedure for, 162–165, 163f–165f quick guide for, 162, 162b SynthoGraft for, 163, 164f, 167, 169f titanium-mesh procedure with, 165–168, 166b, 167f–170f definition of, 151 goal of, 153 internal calcium phosphate coating with, 245–246 crestal window hybrid procedure, 158– 161, 159f–161f goal of, 153 hydroxyapatite coating with, 245–246, 246f implant insertion and seating, 156, 157f presurgical analysis and planning for, 152–153, 153f procedure for, 154–157, 155f–157f quick guide for, 154b radiographic assessments before, 153f, 153–154 SynthoGraft used in, 155f, 155–156, 159, 161, 246 lateral atrophic maxillary ridge treated with, 200 benign sinus lesion managed with, 176, 177b, 177f–179f description of, 151, 170 pedicled periosteal flap used in, 175, 175f postoperative radiograph of, 176f procedure for, 171f–176f, 171–176 quick guide for, 171f radiographic assessments before, 171, 171f–172f SynthoGraft for, 172 subantroscopic laterobasal sinus floor augmentation, 170 vertical approach, 151 Sinus Lift Abutment, 279, 283, 283f Sinus Lift Curette, 174f Sloping shoulder, 11f–12f, 11–12, 15, 284, 317

Slow drilling, 14, 14f, 85, 317 Smad proteins, 41 Smile, 103 Smith, A. E., 4 Socket regeneration definition of, 290

guided bone regeneration and, 296, 297f–298f immediate implant placement versus, 290, 291t of mandibular central incisor, 292–293, 293f–294f of maxillary central incisor, 291f–293f, 291–292 xenografts versus SynthoGraft for, 293– 296, 295f–296f Splinted restorations, 21, 22f Split-thickness flap, ridge splitting with, 191–196, 192f–196f Squamous cell carcinoma, 265f–269f, 265–269 Stealth Abutments, 18, 18f Stone model, surgical template created from, 88, 88f Stress and strain, 57–59, 58f Stress shielding, 32 Stryker Precision Fin Implant, 8–9 Subantroscopic laterobasal sinus floor augmentation, 170 Submandibular fossa, 101 Subperiosteal implant appliance, 209, 210f Sulcus Formers, 125, 125f Sulcus forming, 125 Surface area, 248 Surgical procedures guided surgery, 98–99, 99f–100f, 100b single-stage, 95, 95b two-stage. See Two-stage surgical procedure.

Surgical templates, for Bicon implant placement, 87–88, 88f–89f Survival rates Bicon implants, 75–76, 76t long implants, 82, 83f long-term treatments, 81–82, 82f–83f short implants, 75–76, 76t, 82, 83f Synthodont implant, 6–7, 7f, 9 SynthoGraft autologous bone versus, 290 cellular response to, 289f clinical applications of bone voids, 280, 280f crestal window sinus lift, 163, 164f description of, 290 guided bone regeneration, 309, 309f–310f, 314 internal sinus lift procedure, 155f, 155– 156, 159, 161, 246 maxillary ridge splitting with splitthickness flap, 193, 193f socket regeneration, 290–296, 291f–296f description of, 318 porosity of, 289 preparation guidelines for, 290, 290f xenografts versus, 293–296, 295f–296f

T Tapered integrated screw implant-abutment interface bacterial leakage at, 68 description of, 27, 28t, 49, 50f design of, 64, 64f load carrying and transfer characteristics enabled by, 51 microbial leakage at, 51, 59 peri-implant bone stress affected by, 51–52 Tapered-interference fit definition of, 50, 64 design considerations of, 52 efficiency of, 55 insertion force of, 54f, 54–55 literature survey of, 50–52 load carrying and transfer characteristics enabled by, 51 mechanics of, 52–55, 53f–55f peri-implant bone stress affected by, 51–52 pull-out force of, 53f, 53–55, 54t Telescopic copings, 144, 145f Telescopic prostheses case study of, 255f mandibular full-arch, 147f–148f, 147–148 maxillary full-arch, 147f–148f, 147–148 TRINIA, prefabricated titanium copings for, 19, 19f without primary castings, 23 Threaded implants Bicon implant versus, 279, 284 description of, 6 torquing of, 26 Thrombin, 39f Thrombogenesis, 39f Ti-6Al-4V, 26, 30 TIF. See Tapered-interference fit. Titanium biologic response to, 30 commercially pure, 26 description of, 29–30 Ti-6Al-4V, 26, 30 Titanium abutment bone-loading platform switching, 247 crown and, interface between, 20, 20f hemispheric base of, 247 load transfer, 247 surface treatment of, 30 surgical placement of, 93–94, 94f Titanium implants Brånemark’s studies of, 6 Titanodont implant, 7, 7f, 9 Titanium-mesh procedure, crestal window sinus lift with, 165–168, 166b, 167f–170f Titanodont implant, 7, 7f, 9 Tooth transplantation, 3 Trainin, Boris, 2 Transforming growth factor-ß, 39–40 Treatment(s) adolescents, 117f–121f, 117–121 anterior implant placement, 108–113, 109f–112f atrophic maxillary ridge, 205f–213f, 205–212 bone voids, 281f–284f, 281–284 Integrated Abutment Crowns, 183, 186f, 236, 236f–237f, 249, 249f–250f, 303f, 313, 314f long implants, 82, 83f long-term, 81–82, 82f–83f mandibular first molar, 76, 77f mandibular right incisor, 81, 81f maxillary anterior implant, 108–110, 109f–110f maxillary central incisors, 78f–79f, 78–79 maxillary first molar, 76, 77f, 82, 82f maxillary right lateral incisor, 79, 80f maxillary second molar, 76, 77f peri-implant disease, 71f–72f, 71–73 telescopic prostheses, 255f Treatment planning bone quality assessments, 86f, 86–87 implant size, 86, 86f ß-Tricalcium phosphate, 288–289, 289f, 314 TRINIA bond strength of, 140 characteristics of, 140 colors of, 140, 140f composition of, 140 definition of, 22f, 202, 318 description of, 8 flexural modulus of, 140 flexural strength of, 140 indications for, 23 TRINIA prostheses atrophic mandibular ridge treated with, 219–223, 220f–223f, 227–228, 228f atrophic maxillary ridge treated with, 202f–204f, 202–203, 206, 207f, 209, 209f, 211f–213f, 211–212

in bone marrow transplantation patient, 260f in denosumab therapy patient, 262f fixed partial denture, 141f intraoral seating of, 146 in irradiated bone patients, 271, 271f, 273, 273f maintenance of, 23 mandibular full-arch description of, 147f–148f, 147–148 screw-retained, 142f in mandibular squamous cell carcinoma patient, 269f maxillary, 143f–144f, 147f–148f, 147–148 partial dentures, 144 provisional stabilizing prosthesis, 97f, 96–98

relining of, 23, 23f, 143f–144f techniques for, 140, 141f–144f telescopic in bruxism patient, 232, 232f description of, 144–147, 145f–147f prefabricated titanium copings for, 19, 19f support recommendations for, 148 Tumor necrosis factor-α, 39–40 Two-stage surgical procedure, for Bicon implant placement abutment placement, 93–94, 94f bone harvesting during reaming, 91, 91f–92f implant placement, 92, 92f implant uncovering, 92–93, 93f osteotomy, 90, 90f papillae-sparing flap used in, 89f pilot drill depth, 90, 90f quick-reference guide for, 95b reamers used in, 90–92, 91f removal of healing plug, 92f, 93 site preparation, 88, 89f–91f, 90–92

temporization sleeve, 94f, 94–96 Two-stage window technique, ridge splitting with, 186–190, 187f–190f

Type I bone, 86, 86f Type II bone, 86, 86f Type II diabetes mellitus, 258, 259f Type III bone, 86, 86f Type IV bone, 86, 86f

U

Universal Abutment crowns on, 126, 127f–129f description of, 8, 18–19, 124 design of, 18–19 geometry of, 124 hemispheric base of, 13–14 illustration of, 18f locking-taper implant-abutment interface benefits for, 12 360 degrees of positioning for, 12, 13f, 28

V

Vacuum-formed surgical template, 87–88, 90, 90f Vascular endothelial growth factor (VEGF), 40 Venable, C. S., 5 Vitallium, 5

W

Weekley, Fred, 10 Weibell modulus, 32f Wide-diameter short implants, 52 Wolff, Julius, 199 Wolff’s law, 9, 199 Woven bone, 42

X

Xenografts description of, 288 SynthoGraft versus, 293–296, 295f–296f

Y

Yttria-tetragonal zirconia polycrystal, 31–32

Z

Zirconia copings, 137f Zirconia crowns, 128f Zirconia-veneered restorations, 30–31, 31t Zygomatic implants, for atrophic maxillary ridge, 201f–202f, 201–202, 204f

This book offers not only a history of dental implants and the science of osseointegration but also a retrospect of the Bicon dental implant that covers more than 30 years. In this time, the unique implant design has remained essentially unchanged, and the vast collection of clinical examples presented here aptly demonstrates Bicon’s unmatched clinical capabilities.

Bicon is a surgical-grade titanium press-fit implant with a scientifically explained and time-proven unique macrogeometric design. This design provides treatment opportunities for the benefit of clinicians, technicians, and most importantly patients by offering simple, predictable, and effective techniques that almost always avoid the time, cost, and morbidity of bone-grafting procedures and complicated prosthetic restorations.