Research Abstracts

Sinus Augmentation Procedure Using Beta-Tricalcium-Phosphate: Histological Analysis of Grafted Bone at Time of Implant Placement

American Academy of Periodontology 94th Annual Meeting & Exhibition | Seattle, WA  | September, 2008
Ulrike Schulze-Späte¹, Thomas Dietrich^{1, 2}, Justine Dobeck³, Rayyan Kayal¹, Adrian Time¹, Ziedonis Skobe³, Serge Dibart^1
1Department of Periodontology and Oral Biology, Goldman School of Dental Medicine, Boston University, Boston, MA,
²University of Birmingham, UK
³The Forsyth Institute, Boston, MA

BACKGROUND: Implant placement in the edentulous maxilla often represents a clinical challenge due to insufficient bone height after crestal bone resorption. Several graft materials have been evaluated for augmenting the maxillary sinus in order to compensate for the lost vertical dimension. Allografts are readily available, there is no risk of disease transmission and they do not require a second site surgery.The aim of this study was to evaluate the development and maturation of augmented bone in the maxillary sinus using beta-tricalcium phosphate.
MATERIAL AND METHODS: Patients (n=10, female: 4/male 6, age 30-64) with the need for rehabilitation of their dentition in the posterior maxilla and no present medical contraindications were included in the study. Beta-tricalcium phosphate (SynthoGraft, Bicon, Boston, MA) mixed with the patient’s blood was implanted into the sinus cavity, which was accessed using a lateral window technique. 6-8 month post sinus elevation, bone biopsies were taken and implants were placed simultaneously. All specimens were demineralized and subjected to staining procedures (H&E, Goldner's staining, TRAP). Slides were analyzed using lightmicroscopy for total surface area, the surface area that consisted of bone and the surface area that consisted of graft material (all in mm2 and expressed as % of the total surface.). Osteoclasts were identifiedand counted as number per mm2.
RESULTS: All implants were placed achieving primary stability and restored 4 months after placement. H&E and Goldner's stainings demonstrated the presence of vital woven bone in the grafted area withonly a few remaining graft particles (total bone surface: 31.3%±15.8% at 6 month and 36.4%±5.4% at 8 month, total graft surface:13.9%± 4.7%at 6 month and 9.6%±4.8%). In addition, TRAP staining revealed presence of osteoclasts surrounding those particles (osteoclast number:1.23±0.25 per mm2 at 6 month and 1.4±0.4 per mm2 at 8 month). A lack of inflammatory reaction was noticed with the use of this graft material. During 12 month follow up, no implant failure or complications were observed.
CONCLUSIONS: Beta-tricalcium-phosphate has the advantage of exhibiting no risks of disease transmission and can be available in unlimited quantities. It is clinically easy to use, having great handling properties and appears to cause no persistent inflammatory reaction insurrounding bone. Overall this material seems to provide adequate stability at time of implant placement. Therefore, augmentation of the maxillary sinus with beta-tricalciumphosphate represents a viable option for increasing vertical bone height in the posterior maxilla prior to implant placement.

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Crown-Implant Ratios of 6mm Length Implants

Academy of Osseointegration 2008 Annual Meeting | Boston, MA | February, 2008
Hardeep (Bobby) Birdi, DMD ◆ John Schulte, DDS, MSD ◆ Alejandro Rodriguez-Kovacs, DDS ◆ Meghan Weed, RDH ◆ Sung-Kiang Chuang, DMD, MD
University of Minnesota School of Dentistry

INTRODUCTION: Unfavorable crown-implant ratios have not yet been established. Still, excessive crown-implant ratios have been cited in the literature as being detrimental to long term implant success. The primary aim of this study was to determine the crownimplant ratios of single implant-supported fixed restorations on 6mm length implants in a clinical practice, and to evaluate the health of these implants via mesial and distal bone levels. Additionally, the relationship between crown-implant ratio and proximal bone levels was to be evaluated.
MATERIAL AND METHODS: In this retrospective cohort study the cohort was composed of 314 patients possessing at least one single 6mm length plateau design implant supported fixed restoration which had been surgically placed between Feb 1997 and Dec 2005. A chart review was performed to acquire radiographs in which both the entire crown and implant were visible. The length of the crown and implant were measured directly from the radiographs using consistent magnification to calculate the crown-implant ratio. Also, the mesial and distal bone levels were measured using 3 times magnification and mathematically corrected for distortion. The last available radiograph was used to measure bone levels. Follow-up time was calculated from the day of implant placement, to the last available radiograph. Statistical analyses using analysis of variance mixed models were used.
RESULTS: Data from 534 single implant supported fixed restorations were tabulated and included in the study. The mean (SD) follow-up time was 15.8 (19.2) months, with a range of 0.01 to 99.2 months. The mean crown length (SD) was 13.3 (2.7) mm, with a range of 2.4 to 21.7 mm. The mean (SD) crown-implant ratio was 1.97 (0.4) and ranged from 0.36 to 3.2. The average mesial and distal bone levels (SD) measured from the final radiographs were -0.2 (0.7) mm and -0.2 (0.9) mm respectively. There was no statistically significant relationship between increasing crown-implant ratios and decreasing mesial and distal crestal bone levels around the implant with p-values of 0.94 and 0.57 respectively.
CONCLUSIONS: The results of this study suggest crown-implant ratios do not affect long term success of 6mm length implants. Also, there are no associations between crown-implant ratio and crestal bone levels.

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Preliminary Results of the Survival of 5 x 6 mm Implants

Academy of Osseointegration 2008 Annual Meeting | Boston, MA | February, 2008
Augusto Saldarriaga, DDS • Michael R. Markiewicz, BS • John Schulte, DDS, MDS • Meghan Weed, RDH • Sung-Kiang Chuang, DMD, MD
University of Minnesota School of Dentistry

INTRODUCTION: Manufacturers of dental implants have introduced short implants for use in areas of vertical alveolar bone deficiency. The literature regarding the survival of short implants is mixed. Recent modifications in the geometric shape and surface treatments of short implants may contribute to a rate of survival comparable to their longer counterparts. The objective of this study was to determine the short term survival of a 5 x 6 mm plateau designed dental implant.
METHODS: A retrospective cohort study design was used. The cohort consisted of patients who received one or more 5 x 6 mm plateau designed implant inserted between January 2005 and August 2006 at a private practice clinic. A chart review was conducted to acquire data on patient demographics, implant location, bone density, length of time in function and/or implant failure. The primary outcome variable was implant failure. Survival time was defined as the time between the date of implant placement and last appointment or the date of implant removal for any reason. Descriptive statistics are reported.
RESULTS: The sample included 542 implants placed in 324 patients (52.8% female). Mean patient age was 56.6 + 13.1 years. All 5 x 6 mm plateau designed implants were placed using a two stage technique. 301 (56%) implants were placed in bone density three and 151 (28%) implants in bone density four. 226 (41%) were placed in the posterior maxilla and 265 (49%) in the posterior mandible. The average follow-up time the implants were in function was 13.3 + 8.4 months, range 0.1 to 30.4 months. 35 failures were recorded for a survival rate of 92.1%. 20 (57%) of the failed implants were placed in type three bone density and 13 (37%) in type four density bone. 17 (49%) of the failures were in the posterior maxilla and 11 (31%) in the posterior mandible.
CONCLUSION: The short term survival of the 5 x 6 mm plateau designed implant is encouraging. Additional observation time is necessary to establish long term survival rates.

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Crestal Bone Level and its Association With Varying Densities of Bone

Academy of Osseointegration 2008 Annual Meeting | Boston, MA | February, 2008
Sujey Rodriguez-Lozano, DDS • John Schulte, DDS, MDS • Meghan Weed, RDH • Sung-Kiang Chuang, DMD, MD
Graduate Prosthodontics, University of Minnesota School of Dentistry

INTRODUCTION: Crestal bone levels associated with dental implants are an indication of the health or status of the implant.
PURPOSE: The purpose of this study was to evaluate crestal bone levels on plateau designed implants in various densities of bone.
METHODS: A case series study design was used. The sample was composed of patients who had single tooth implant supported restorations placed between February 1997 and August 2006 with densities of bone information available in the charts. Bone levels on the mesial and distal surfaces of the implants were established by direct measurement from the top of the implant to the radiographic position of the bone on the implant surface. Radiographs were mathematically corrected for distortion. Bone density was determined objectively by examination of the bone which collected on the flute of the reamer during preparation of the osteotomy. Type I bone was characterized by bone which had minimal blood content, type II bone by blood wetted bone in the reamer, type III bone by a partially filled reamer of blood wetted bone and type IV bone as a reamer devoid of bone. Descriptive statistics were computed and data was analyzed with analysis of variance mixed models.
RESULTS: The sample consisted of 214 patients (50.0% females), Average age of the patients was 56.6 years. 264 plateau designed implants were included in this study. 50 implants were placed in type II bone density, 117 implants were placed in type III bone density and 97 were placed in type bone IV bone density. The mean age of implants was 2.3 ± .8 years. Mesial and distal bone levels in each of the 4 types of densities was reported as: For density type II: mesial -.9 ± .6 mm and distal -.9 ± .6 mm. For density type III: mesial -.8 ± .7 mm and distal -.8 ± .9 mm. For density type IV: mesial -.8 ± .6 mm and distal -.8 ± .5 mm. Statistical testing reveals no statistically significant differences in mesial bone levels (P=0.38) and distal bone levels (P=0.79) between the three groups of bone densities.
CONCLUSIONS: This study suggests that the crestal bone loss associated with the plateau designed implant is well within guidelines established in the literature. Secondly, there is no statistically significant difference in the crestal bone levels when comparing various densities of bone. The results of the study are relevant only to the plateau design implant.

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In Vivo Evaluation of Implant Length and Surface Physico/Chemistry Characteristics in Biomechanical Anchorage in Plateau Root Form Implants. An Experimental Study in Beagle Dogs.

Academy of Osseointegration 2008 Annual Meeting | Boston, MA | February, 2008
Granato R, Marin C, Suzuki M, Gil JN, Coelho PG

Introduction: Since the implant surface is the first part of the implant that interacts with the host, significant attention has been devoted towards increasing the biocompatibility and osseoconductivity of implant surfaces. Surface modification approaches have been successful in increasing the host response to surgical implants, resulting in higher bone-to-implant contact (BIC) and higher bone mechanical properties at early implantation times. Among surface chemistry modifications, the incorporation of Ca- and P-based bioceramic onto the implant surfaces through various manufacturing processes has been investigated throughout the last two decades. These basic and clinical investigations have shown that bioceramic coated implants presented higher degrees of osseoconductivity and attained higher degrees of biomechanical fixation at earlier implantation times compared to uncoated implants. The objective of this study was to determine the influence of implant length and surface chemistry (Alumina-blasted/acid-etched (AB/AE) vs. Nanotite (Na) bioceramic deposition) on the biomechanical fixation of plateu root form implants in a beagle dog tibia model.
Methods: 4.5x11 mm (L) and 4.5x6 mm (S) plateau root form implants of AB/AE and Na surfaces were placed bilaterally along the proximal tibia of 6 beagle dogs and remained for 2 and 4 weeks in vivo (n=9 per implant length, surface, and time in vivo).(Fig. 1 and 2) Following euthanization, the implants were torqued to interface failure at ~0.445 radians/sec.(Fig. 3 and 4) ANOVA was utilized to determine the effects of implant length, surface, and time in vivo as (independent variables) on torque to interface failure (dependent variable). One-wayANOVAwas utilized for direct comparison between groups.A95% level of significance was used.
Results: trans-surgical bone preparation showed that L implants engaged two bone corticals whereas S implants engaged one cortical. ANOVA showed that all independent variables presented a significant effect in torque to interface (Ncm) failure: Implant length (P<0.0005, S=43.75±11.02 , L=72.02±10.54 ), implant surface (P<0.0000, AB/AE=34.93±10.85 , Na=80.84±10.7 ), and time in vivo (P<0.002, 2W= 45.51±10.7 , 4W=70.27±10.85 ). One-way ANOVA showed significant differences between groups (P<0.0000, seeTable 01).
Conclusions: According to the results obtained, the Nanothickness bioceramic surface coating played a significant role on biomechanical fixation of L and S implants at both times in vivo. While ANOVA showed a significant effect of implant length on biomechanical fixation, direct comparison between groups showed that this difference was larger for Nanotite coated implants, and not significantly different for uncoated implants.

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A Comparison of Crestal Bone Levels in Immediate Versus Delayed Loaded Implants

Academy of Osseointegration 2008 Annual Meeting | Boston, MA | February, 2008
Cary D. McNeil, DDS ■ John K. Schulte, DDS, MSD ■ Meghan Weed, RDH ■ Sung-Kiang Chuang, DMD, MD
University of Minnesota School of Dentistry

INTRODUCTION: The results of implant survival studies as they relate to immediate versus delayed loading are inconclusive. Some report greater failure rates with immediate loading and others show no difference between the two procedures. Implant failure is often associated with excessive bone loss over time. As a result, bone loss over time may be a critical measurement of implant health. The objective of this study was to determine if there were differences in crestal bone levels over time with immediately loaded plateau design implants compared with delayed loaded plateau design implants.
METHODS: A retrospective cohort study was used. The cohort consisted of patients who received a single tooth plateau designed implant, immediate or delayed loading, between January 1997 and July 2005. Digital radiographs were retrieved from patient records. Mesial and distal bone levels were measured directly on the radiographs using 3x magnification and mathematically corrected for distortion. Changes in bone levels over time were calculated by comparing levels at post-integration with the last available film. Analysis of variance mixed models adjusted for clustered effects was used to test for statistical significance between the two groups.
RESULTS: A total of 483 implants were included in this study. The initial radiographic measurement of bone levels was set at 10 months after implant placement and was followed with a mean follow-up time of 19.3 months. The mean patient age was 55.3 years and 48.9% were female. There were 204 implants which were immediately loaded and 278 implants which were delayed loaded. Mean changes in mesial and distal bone levels for the immediately loaded implants were 0.19mm ± 0.7mm and 0.27mm ± 0.7mm respectively. For the delayed loaded implants, the mean mesial and distal bone levels were 0.14mm ± 0.7mm and 0.09mm ± 0.6mm respectively. No statistically significant differences were found in crestal bone levels over time in the immediately loaded implants compared with the delayed loaded implants (mesial changes in bone levels p=0.70, distal changes in bone levels p=0.12).
CONCLUSIONS: Using bone level changes over time as a criterion to measure implant health, there was no statistically significant difference between immediate and delayed loaded plateau design implants. An increase in bone levels was recorded for both groups.

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Changes in Crestal Bone Levels Associated with a Bacterially Sealed Screwless 1.5˚ Locking-Taper Implant to Abutment Connection

2007 ACP Annual Session | Scottsdale, Arizona | October, 2007
Sujey Rodriguez-Lozano, DDS
Graduate Prosthodontics, University of Minnesota School of Dentistry

Introduction: The microgap associated with a screw-retained implant-abutment connection is often cited as the reason for crestal bone level changes around dental implant-supported restorations. The design of the implant abutment connection may influence crestal bone loss. The purpose of this study was to evaluate crestal bone levels for 50 bacterially sealed locking-taper implants to abutment connections at 3 periods of time after implant placement.
Methods: A retrospective case series study design was used. The sample (33 patients , 50 implants) was randomly selected from patients who received immediately loaded implants between February 2002 and November 2005. The study measured and compared bone levels on the mesial and distal aspect of the implant-abutment connection at three periods of time: time 1- immediately after implant placement, time 2- at least 7 months (post-integration) after placement and time 3- most recent radiograph available but at least 14 months after placement. Descriptive statistics were use to report the results.
Results: The sample consisted of 33 patients who collectively had 50 immediately loaded implants placed. The mean age of the implants was 2.3 ± .82 years. Mean changes in bone levels on mesial (m) and distal (d) surfaces at time: (1), (2) and (3) were reported as: The mean differences for bone levels on mesial and distal surfaces between time (2) and (1) was: on the mesial, 0.3 ± 0.7 mm and on the distal, 0.4 ± 0.6 mm. The mean differences for bone levels on mesial and distal surface between time (3) and (1) was : on the mesial, 1.0 ± 2.1 mm and on the distal, 1.2 ± 2.1 mm. The mean differences for bone levels on mesial and distal surface between time (3) and (2) was : on the mesial, 0.2 ± 0.7 mm and on the distal, 0.2 ± 0.7 mm.
Conclusion: An increase in mesial and distal crestal bone levels was found during the observation period. This could suggest that the bacterially sealed screwless 1.5˚ locking-taper implant to abutment connection may have an important role in maintaining crestal bone levels around implants of this design.

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Histomorphometry of Explanted Dental Implants

IADR | New Orleans, LA | March, 2007
J. Lemons, M. Anabtawi, P. Beck, and V. Morgan
Department of Prosthodontics, School of Dentistry University of Alabama at Birmingham

Objective: The significant success (%) and longevities of root form dental implants affords opportunities to evaluate and classify device-to-bone interfaces. These opportunities are based on a small percentage that come to revision. Histomorphometric analyses of human explants permits multiple comparisons including in vitro and laboratory in vivo study outcomes.
Methods: A clinical group (headed by VM) have removed root form implants, where indicated clinically, by Magnitudes of osseous integration from three time periods (about 2, 5 and 10 years) are shown in Figure 2 (A-C) trephine osteotomy. The implant body and bone remain in bloc and specimens were immediately fixed in 10% buffered formalin and transferred with selected records for analysis. Specimens were: macrophotographed, evaluated stereomicroscopically; oriented, embedded; prepared by Exakt® sectioning; stained; and evaluated along longitudinal mid-line thin (20-50 micrometer) sections by Bioquant® imaging for bone quality, quantity, and specific anatomical characteristics.
Results: Eighty* plateau-type design received from one source over the past 3 years. Specimens evaluated by staff and students resulted in: (1) adequate bone for 41 longitudinal section histomorphometric analyses; (2) percent bone integration from 5 to 95% that was not significantly correlated (p>0.05) with in vivo factors other than anatomical location; and (3) interfacial bone structures of a mature and osteonal-type anatomy reported previously1. These results support that dental implant-to-bone interfaces can be stable over time and function with bone remodeling leading to a functional anatomy that is characteristic of the implant design. Comparative analyses with screw-type designs of the same biomaterial are scheduled.
Conclusions: (1) en bloc explants from in vivo functional periods from 3 to 126 months showed osseointegration percentages from 5 to 95%; and (2) the bone anatomy was a mature osteonal type structure, characteristic of plateau type implant designs.

Partial student support from Bicon, Boston, MA is acknowledged.
Lemons, J, J Oral Imp, 2004 and in Davies, J. Ed., Bone Engineering, 2000.

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Histological Analysis for forty one retrieved dental implants

IADR | New Orleans, LA | March, 2007
Muna Anabtawi, Preston Beck, Al Bartolucci, Vincent Morgan, Jack Lemons
Department of Prosthodontics, School of Dentistry University of Alabama at Birmingham

Objectives: To analyze the anatomy and osseous integration status of the hard tissue interfaces for retrieved implants, and to interpret the clinical status of this specific implant patient population through correlating bone integration status and demographical data.
Methods: Eighty dental implants removed for clinical reasons were retrieved from patients over a 3 year period. Forty one explants were selected for histological analysis because they had adequate bone for longitudinal section analyses. Specimens were processed, embedded in plastic, and thin (20-30 micrometer) ground sections were made along the long axis of the implants. Specimens were stained with Sandersons’ Bone Stain. Blinded histomorphometric analysis was performed to measure the percentage of bone area between the plateaus and the bone/implant contact (BIC). Patient records (gender, date of birth, smoking status, time in vivo, type of implant surface, presence of augmentation, and position of the implants in the jaw) were collected and incorporated into the histomorphometric data; and statistical analysis was performed.
Results: There were no strong associations between any of the clinical, patient and implant variables and the bone area percentage and (BIC). In a multiple regression analysis adjusting for the available data, the anterior position was marginally significantly associated with higher percentage of bone and (BIC) (p=0.067). Performing a simple pair wise correlation, females had higher percentage of bone than males (p=0.0898).
Conclusions: The findings support that the success and failure can be caused by a combination of factors not associated with bone integration status. Revision procedures represent a small percentage of dental implants treatment and this study demonstrates that larger numbers of specimens will be required for statistical significance amongst the variables considered.

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Investigation of maxillary sinus bone graft healing by MicroCT

IADR | New Orleans, LA | March, 2007
P.M.C. CHOPRA¹, M. JOHNSON¹, P. BECK¹, T. NAGY¹, M. MARINCOLA², and J.E. LEMONS¹,
¹Department of Dental Biomaterials, School of Dentistry University of Alabama at Birmingham
²Rome, Italy

Objectives: A MicroCT analysis of bone healing quality and quantity subsequent to placement of a reformulated tricalcium phosphate (TCP)* in maxillary sinus ridge augmentation.
Methods: Ten(10) trephined rod shaped human bone cores were obtained from an independent source at three months after the placement of tricalcium phosphate particulate in the maxillary sinus for ridge augmentation prior to implant placement. The samples were immediately stored in 10% neutral buffered formalin. Using SCANCO 40 MicroCT machine, the samples were evaluated at resolutions of 6 and 20µm respectively. The threshold for bone and graft material was determined using visual image, intensity (grey level) and histogram analyses. The density and three dimensional micro architecture of the bone and graft material were analyzed using the software which was interactive with the investigators.
Results: The samples were investigated for micro architecture and density of the bone and graft material. Along with mineral density, the trabecular bone parameters such as Trabecular thickness (Tb Th), Trabecular separation (Tb sp), Structural Model Index (SMI), Trabecular number (Tb no), and connectivity density were obtained for each sample and analyzed ANOVA (p≤0.05). The results obtained at both resolutions (6and 20µm) were comparable, however parameters obtained at 20µm will be used in the future studies including histological, histomorphometrical and scanning electron microscopy comparisons.
Conclusions: MicroCT allowed the study of bone both quantitatively and qualitatively without destroying the samples. These results demonstrated an osteoconductive effect of TCP. The mean bone and graft volume obtained was 25.5 and .43 mm3 respectively; suggesting new bone formation and graft dissolution. These results corroborate independent reports of implants having moved to functional status without failures. The data achieved can be further used to correlate with the values obtained from the traditional histological methods.

*SynthoGraft

Partial student support from Bicon, Boston, MA is acknowledged.

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Assessment of Periodontal Health Around Integrated Abutment Crowns

AAP Annual Meeting, San Diego, CA, September 2006.
Cheng, K.K., Chuang, S.K., Weed, M., Dibart, S.

Background: The Integrated Abutment Crown™ (IAC) (Bicon, Boston MA) is a cementless, screwless implant-supported crown made from a polyceramic material, which is 80% glass and 20% PEX resin. Unlike the porcelain fused to metal crown (PFM), the IAC restoration is fused to the abutment thus eliminating the presence of a crown/abutment microgap. The purpose of the present investigation was to compare various periodontal parameters in patients with IAC, natural teeth (NT), NT restored with PFMs, and implants restored with PFMs.
Materials & Methods: A retrospective cohort study was conducted on patients evaluated from January, 2003 to April, 2005 at the Implant Dentistry Centre – Faulkner Hospital (IDC-FH), Boston, MA. Natural teeth/implants of these patients were separated into 4 groups: Group 1 (NT), Group 2 (NT/PFMs), Group 3 (implants/PFMs) and Group 4 (implants/IACs). Periodontal parameters including modified plaque index (MPI), sulcus bleeding index (SBI), gingival index (GI), and the average of 6 probing depths (PD) from each tooth or implant (MF, F, DF, ML, L, and DL) were recorded at initial and final examinations. Linear mixed-effects models were used to evaluate the associations between the four groups (the main predictor) and clinical periodontal parameters over the follow-up time. A p-value ≤0.05 was considered statistically significant.
Results: TThe sample included 50 patients (22 males, 28 females) with a mean age of 64.2 years (range = 31.65 - 95.16 years) that were observed over a mean follow-up period of 23.07 months (range of 9.99 -26.28 months). A total number of 375 teeth/implants were divided into: Group 1 (105 NT), Group 2 (63 NT/PFMs), Group 3 (68 implants/PFMs) and Group 4 (139 implants/IACs). The mean changes in clinical periodontal parameters of each group were compared to a reference group (Group 1). Gingival index: Group 3 > 2 > 1 > 4. Average probing depth: Group 1 > 2 > 4 (p<0.05) ≈ 3 (p<0.05). (Difference between group 3 and 4 was not statistically significant.) Sulcus bleeding index: Group 4 > 2 > 1 > 3. Modified plaque index: Group 4 (p<0.05) > 2 > 1 > 3.
Conclusion: Group 4 had the most significant decrease in GI compared to the other groups and performed similarly to Group 3 in terms of probing depths. There were no statistical differences with respect to mean change of SBI among the four groups. Group 4 was found to have a significantly higher MPI score compared to Group 1. Further studies evaluating the plaque composition will be necessary in the near future to explain these findings.

An Innovative Immediate Stabilization Technique For Dental Implants

FDI World Dental Congress | Shenzhen, China | September, 2006
Drauseo Speratti, DDS; Meghan Weed, RDH; S.K. Chuang, DMD

Introduction: Several techniques for the immediate stabilization and functioning of dental implants have been used and described over the years. This study demonstrates how effective this procedure can be done, showing the ease with which quality aesthetic results can be achieved without any additional comprehensive laboratory procedures for the provisional phase. A screwless implant/abutment connection improves the efficiency and effectiveness of the procedures. Regular restorative procedures provide the final restoration.
Materials & Methods: The sample was compose of 505 patients who had a total of 1086  implants placed. We used a retrospective cohort study design including patients who had one or more implants placed using the technique of Immediate Stabilization or Loading between November 1999 and January 2006.
Results: The overall lifetime proportional rate was 91.61%.
Conclusion: This study demonstrates how this technique can be efficient and cost effective, allowing patients to function without the need for removable appliances during healing period, significantly reducing operative time.

Conditional Cox Frailty Predictions Within Clusters for Dental Implant Survival

International Association of Dental Research, Brisbane, Australia June 2006.
Chuang, S.K., Cai, T.

Objectives: The purpose of this study was to conduct conditional and joint predictions for the survival of future dental implants using subject level, implant specific covariate information, and the survival information of other implant(s) for the same subject.
Material and Methods: A retrospective cohort study design was conducted. The cohort consisted of subjects having at least one Bicon implant placed. Covariates information used included smoking status, timing of placement, and implant staging were previously identified using an innovative Cox frailty regression model that adjusted for within subject correlations and heterogeneity of implant failure risks.
Results: The cohort composed of 677 patients with 2349 implants placed. To improve the prediction accuracy, we utilized information on the survival status of existing implants along with the covariates. For illustration, we considered the joint and conditional predictions for the survival of three implants from a single subject who was a non-smoker with immediate implant placement after extraction and one stage protocol. For example, conditional on the first and second implants both surviving for 12- and 60- months given the above parameters, the estimated probability for the third implant surviving for 12- and 60- months was 88.8% (95%CI: 82.4%, 93.0%) and 81.4% (95%CI: 69.5%, 87.7%) respectively. On the other hand, conditional on the first implant surviving for 12- and 60- months, the probabilities that both the second and third implant survived 12- and 60- months were 77.7% (95%CI: 66.3%, 86.0%) and 63.1% (95%CI: 45.0%, 75.2%) respectively.
Conclusion: Conditional and joint survival predictions within subjects are challenging and commonly encountered in dental research. The application of this innovative flexible joint Cox frailty approach allows unique survival predictions about implant failure based on prior information about the survival status of other implants within the same subject.

Survival Analysis of Immediate Stabilization Loading of Screwless Dental Implants

IADR General Session | Brisbane, Australia | June 2006
D. Speratti¹, M. Hirayama¹, M. Weed¹, and S.-K. Chuang², ¹Implant Dentistry Centre, Boston, MA, USA, ²Harvard School of Public Health, Massachusetts General Hospital, Chestnut Hill, MA, USA

Objectives: The study's objective was to evaluate the survival rate and to identify covariates (risk factors) for failure of an innovative and efficient technique for immediate stabilization and loading of dental implants with a locking taper connection.
Methods: To address the research objective, we used a retrospective cohort study design including all patients who had one or more implants placed using the technique of immediate stabilization / loading at Implant Dentistry Centre at the Faulkner Hospital, Boston, MA between June 1999 and October 2005. Covariates for failure were grouped into the following categories: demographics, implant-specific, anatomic, prosthetic, and reconstructive categories. The outcome variable was implant failure defined as explantation. Overall implant survival was evaluated by the Kaplan-Meier analysis and risk factors by the Cox proportional hazards models adjusted for clustered failure time observations.
Results: The sample was composed of 506 patients who had a total of 1099 implants placed. The overall Kaplan-Meier survival rate at 12 and 24 months were 90.0% and 88.6% respectively. The overall lifetime success rate without follow-up time adjustment was 91.6%. Covariates associated with implant failure (p < 0.15) in the univariate analysis included: implant position, diameter, well size, length, and coating of implant. Based on the adjusted multivariate Cox model including age at implant placement and gender, covariates associated with implant failure were implant position, length, and presence of coating on the implant (p < 0.05).
Conclusions: There are many advantages with the use of immediate stabilization and loading implants. The overall one-year survival of the immediate stabilization and loading implant system was 90.0%. After controlling for other variables, implant position (posterior jaw) was associated with an increased risk for implant failure while increased implant length and presence of surface coating on the implant were associated with a decreased risk for implant failure.

Immediate Stabilization of Implants for General Dentists

ADA Annual Meeting | Philadelphia, PA | October, 2005
Speratti, D.

Immediate stabilization and function of dental implants has become a preferred method of treatment. Clinical research and engineering improvements have allowed clinicians to offer the treatment more frequently. Leading practitioners utilize the method of “Immediate Loading or Stabilization”. This presentation intends to show a predictable and affordable technique for general practitioners so that they may be able to achieve aesthetic results without additional surgical procedures. Clinical pictures will be presented.

Immediate Stabilization & Function of Dental Implants

FDI Annual Meeting | Montreal, Canada | August, 2005
Speratti. D., Hirayama, M.

Abstract: Immediate Stabilization and Function (ISF) of dental implants has become a preferred method of treatment. Clinical research, engineering improvements, and patients’ needs have allowed clinicians to offer the treatment more frequently. Leading practitioners utilize the method of “Immediate Loading or Stabilization”; however, many clinicians are still skeptical about its success.
Materials and Methods: In this on-going clinical study of 405 fin-type implants (Hydroxylapatite and Titanium Plasma Spray), 142 patients were treated from November 1998 to July 2004 by means of the ISF.  All implants were immediately stabilized by fabrication of a temporary prosthesis bonded to natural dentition or splinting implants to one another.
Results: During this period of time, 128 implants successfully integrated and were restored.  14 failed to integrate and were replaced.
Conclusion: With this technique, a clinician may provide immediate temporary restorations of implants in function at the same time of implant placement without additional risks impacting the success of treatment.

Fit of Fixture/ Abutment Interface of Internal Connection Implant Systems

AO Annual Meeting | Orlando, FL | March, 2005
Kim, C., Gwangju, Chung.

Objective: The purpose of this study was to evaluate the machining accuracy and consistency of implant/ abutment/screw combination of internal connection type.
Materials and Methods: In this study, each two randomly selected internal implant fixtures from ITI, 3i, Avana, Bicon, Friadent, Astra, and Paragon system were used. Each abutment was connected to the implant with 32 Ncm torque value using a digital torque controller or tapping. All samples were cross-sectioned with grinder-polisher unit (Omnilap 2000 SBT Inc) after embedded in liquid unsaturated polyester (Epovia, Cray Valley Inc.) Then optical microscopic and scanning electron microscopic (SEM) evaluations of the implant-abutment interfaces were conducted to assess quality of fit between mating components.
Results: 1. Generally, the geometry of the internal connection system provided for a precision fit of the implant/abutment interface. 2. The most precision fit of the implant/abutment interface was provided in the case of the Bicon System which has no screw. 3. The fit of the implant/abutment inte3rface was usually good in the case of ITI, 3i and Avana system and tha amount of fit of the implant/ abutment was similar to each other. 4. The fit of the implant/ abutment interface was usually good in the case of Friadent, Astra and Paragon system. The case of Astra system with the inclined contacting surface had the most intimate contact among them. 5. Amount of intimate contact in the abutment screw thread to the mating fixture was larger in assembly with two-piece type which is separated screw from abutment such as Friadent, Atra and Paragon system than in that with one-piece type which is not separated screw from abutment such as ITI, 3I and Avana system. 6. Amount of contact in the screw and the screw seat of abutment was larger in assembly of Friadent system than in assembly of Astra system than in assembly of Astra system or Paragon system.
Conclusion: Conclusively, although a little variation in machining accuracy and consistency was noted in the samples, important features of all internal connection systems were the deep, internal implant-abutment connections which provide intimate contact with the implant walls to resist micromovement, resulting in a strong stable interface. From the results of this study, further research of the stress distribution according to the design of internal connection system will be required.

Morphological and Chemical Assessment of Two Thin-film Ion Beam Assisted Deposited Bioceramic Coated Surfaces on Ti-6Al-4V Implants

AO Annual Meeting | Orlando, FL | March, 2005
Coelho, P.G., Lemons, J.E.

Nanotechnology has strongly affected biomaterials science and engineering, once reduced condensed matter domains may deeply alter biomaterials electronics properties and thus their in-vivo behavior. It has been shown that nano-thick Ion Beam Assisted Depoisted (IBAD) bioceramic coatings increase osteoblatic activity at early implantation times, and studies have indicated higher bone-biomaterial interfacial shear strength values for IBAD coated implants. The purpose of this study was to morphologically and chemically assess 2 types of IBAD bioceramic coatings and correlate these evaluations to their in-vivo performance. Control (C) and nano-thick IBAD (IBAD 1, IBAD 2) implants were morphologically evaluated on a SEM under various magnifications, following by survey and site-specific EDS elemental assessment. Superficial layer chemical analyzes were performed by XPS (survey and site-specific), and Ca/P ratios were calculated from spectra output. Results showed no evidence of bioceramic coating presence on all implants (IBAD 1, IBAD 2 –too thin for SEM detection), although ion beam assisted surface etch was evident for IBAD implants. EDS showed the presence of Ti and Al for all specimens, and Ca and P presence for IBAD 2 implants only. XPS spectra showed the presence of Ti, Al, C, O and Si for C implant surfaces, Ti, Al, C, O, Si, Ca, and P for IBAD 1 implant surfaces, and C, O, Si, Ca, and P for IBAD 2 implant surfaces, revealing absorbed molecules (Si and C) for all implants and higher thickness for IBAD 2 implants. Stoichiometry ratios were 1.5 and 2.2 for IBAD 1 and IBAD2 respectively. According to the results obtained, IBAD 2 coatings were thicker than IBAD 1, and both were in the nanorange thickness. Stoichiometry ratios revealed that IBAD 1 and IBAD 2 were different than crystalline HA, suggesting that IBAD coating dissolution rates are potentially higher than crystalline HA. These findings were consistent with animal experiments, where biological response increases were detected at early implantation times due to coating dissolution. Coating nanothickness also allowed direct bone contact to implant metallic substrate, as per histological analyzes, as thin coatings disappear as a function of time in-vivo. IBAD coatings physico/chemical characteristics were desirable features for implant biomechanical fixation competence.

Gingival Tissue Health Around Locking-Taper Implant-Abutment Connections

IADR General Session | Baltimore, MD | March, 2005
Coelho, P.G., Materials Science & Engineering, Birmingham, AL, USA, Geurs, N.C., University of Alabama, Birmingham, USA, Freire, J.N.O., Universidade Federal De Santa Catarina, Florianopolis, Brazil, Coelho, A.L., UNICENP, Curitiba, Brazil, and Speratti, D., Faulkner Hospital, Boston, MA, USA

Objective: to clinically/histologically evaluate gingival tissue around locking taper connected implants in a beagle dog model.
Materials and Methods: Six beagle dogs were acquired 12 weeks prior to surgical procedures. Five weeks prior to euthanization, left mandibular 4th premolars were extracted, followed by immediate placement of two 3.5 mm diameter by 8 mm length endosseous implants at the mesial and distal root sockets. Locking taper abutments were installed to distal implants and the flap was closed by standard suture techniques. Three weeks prior to euthanization, locking taper abutments were installed on left mandibles mesial implants and the same surgical procedure previously described was used to place an implant of same dimensions on the mesial root socket, followed by abutment installation. All surgical procedures were followed by a single dose AB protocol. No mechanical/chemical plaque control was performed, and a crunchy diet was utilized throughout the study. After euthanization, mandibles were retrieved and abutments removed from implants. 5 µm thick soft tissue sections were obtained in the bucco-lingual direction aiming implants' long axis central region (H. and E. stained).
Results: Periodic clinical evaluations revealed absence of inflammation signs. Histological sections resembled healthy mucosal tissue for all 18 specimens. The junctional epithelium was well organized and void of intra cellular spaces. Neutrophils were found and few lymphocytes were noted. No vascular proliferation apical to junctional epithelium was observed.
Conclusion: Histological sections revealed that gingival tissue around locking taper connected implants were consistent with healthy gingival tissue.

Biomechanical Performance of IBAD Thin-Coated Implants at Early Implantation Times

IADR General Session | Baltimore, MD | March, 2005
Coelho, A.L., UNICENP, Curitiba, Brazil, Coelho, P.G., University of Alabama at Birmingham, Birmingham, USA, Freire, J.N.O., Universidade Federal De Santa Catarina, Florianópolis, Brazil, Suzuki, M., University of Alabama at Birmingham, Birmingham, USA., IADR General Session; Baltimore, MD

Desirable features of bioceramic thin-coated implants include controlled composition and thickness plus enhanced adhesion to metallic substrates. Also, metallic substrate exposure with subsequent bone direct contact to the implant surface as a function of time in-vivo may be a potential advantage compared to commercially available bioceramic coatings. Objective: compare the mechanical fixation of Ion Beam Assisted Deposited (IBAD) coated implants versus a non-coated grit-blasted/acid-etched (Control) treated implant surface. Methods: three male adult beagle dogs received 2-4 cylindrical implants on the proximal tibiae following sterile procedures. Left and right limbs provided specimens that remained for 5 and 3 weeks in-vivo respectively. After euthanization, the limbs were retrieved by sharp dissection, the implants received a connecting screw in order to adapt to a torque testing apparatus installed in a universal testing machine. Implants were torqued at a 0.5 in/min rate and maximum loads to interfacial failure were recorded. ANOVA was performed with Max Torque as the dependent variable, and time in-vivo and surface type as independent variables at 95% level of significance. Results: no post-surgical inflammation/infection was observed. Radiographic evaluation revealed bone contact to implant for all groups. Surface treatment had a significant effect on maximum torque value, IBAD= 79.55±7.21 N·cm and Control= 62.76±6.37 N·cm. Time in-vivo did not have a significant influence on maximum torque value, 3 weeks=62.52±6.66N·cm and 5 weeks= 67.23±6.9 N·cm. Conclusion: According to the results, IBAD coated implants presented higher anchorage values compared to control implants, supporting favorable conditions for early functional loading of these implants.

Evaluating the Bacterial Seal of an Implant-Abutment Connection

AAP Annual Meeting | Orlando, FL | October, 2004
Dibart, S.

Background: In the submerged implant design, the quality of the implant-abutment connection is thought to play a critical role in preserving the alveolar crestal bone levels from loss due to oral bacteria. Oral microorganism that would colonize that structure are suspected to initiate inflammation and promote bone loss over time. Methods: In order to test the efficacy of an implant-abutment seal to the bacterial challenge in vitro, a 2 phase experiment was devised. Phase 1: testing the ability of the seal to shield the implant well from outside bacteria. 10 abutments were seated on 10 wide body implants and then immersed in culture tubes containing a bacterial mixture. They were incubated for 24 hours anaerobically at 37°C. The abutments were then separated from implants, carbon coated, and the inside well analyzed for bacteria presence using a scanning electron microscope. Phase 2: testing the ability of the seal to prevent bacterial seepage out from the implant well. 0.1µl of a bacterial mix was deposited at the apical end of abutment posts, which were then carefully inserted into implant wells. The implant/abutment units were immersed, individually, in culture tubes containing a sterile broth and incubated anaerobically at 37°C for 72 hours. The broths were then plated on agar plates to check for bacterial growth.
Results: Phase 1: Scanning electron microscopy did not show any evidence of bacterial presence into the implant wells. Phase 2: There was no evidence of bacterial growth on the agar plates.
Discussion: The tested implant abutment seal was hermetic to oral bacteria in vitro, with no microorganisms transiting from the "outside-in" or the "inside-out".

Aesthetic Dental Implant Restorations

ADA General Session | Orlando, FL | October, 2004
Speratti, D.

Aesthetic restorative procedures on dental implants are known to be complexes and difficult to achieve, challenging clinicians and concerning patients where aesthetic is paramount to their needs. The technique shown in this presentation allowed the clinician to insert a screwless and cementless crown into a dental implant with no gap between the crown and the abutment, bringing an immediate aesthetic result. Clinical pictures will be shown in this presentation.

Comparison of the Periodontal Performance of the Integrated Abutment Crowns, Porcelain Fused to Metal Crowns and Teeth: A 2-year retrospective Cohort Study

Oral Presentation OSSEO | September, 2004
Urdaneta, R., et al.

The Integrated Abutment Crown (IAC) is a technique for the fabrication of single-tooth implant-supported restorations where the abutment and the crown material are one integral unit without the use of any screws or cement. There is no clinically discernible interface between the veneer material and the implant abutment due to a chemical bond. The precision of the prosthetic margin has been shown to be more important for the maintenance of gingival health than its location above or below the gingival margin (Richter and Veno, 1973). It was hypothesized that the gingival tissues would respond positively to a restoration without a crown margin. Purpose: The purpose of this 2-year retrospective clinical study was to compare the periodontal health around Integrated Abutment Crowns, Implant and tooth-supported metal ceramic crowns and adjacent natural teeth. Materials and Methods: 221 implants placed in 62 patients, with a mean age of 58.2 years, 56% were placed in the maxilla and 44% placed in the mandible. Of the prosthetic restorations, 151 were Integrated crowns, 70 were implant-supported Metal ceramic crowns, and 65 were tooth-supported metal ceramic crowns. Patients were recalled and the following periodontal measurements were obtained: Gingival index, modified plaque index, sulcular bleeding index and pocket depth. Results: The 2-year survival rate for Integrated crowns was 98.56%. Two Integrated crowns were removed, one due to implant failure. No significant differences in gingival inflammation and sulcular bleeding were observed between Integrated abutment crowns and unrestored teeth notwithstanding the higher plaque accumulation observed around the Integrated crowns. Furthermore, Metal ceramic crowns on implants had the highest bleeding index and the difference between the Integrated crowns was statistically significant. Teeth, regardless of restoration type, had lower pocket depths than implants. Conclusion: The gingival response around the integrated abutment crowns was similar to the health of the marginal tissues surrounding unrestored teeth. There was significantly less bleeding upon probing around Integrated abutment crowns than around implant supported metal ceramic crowns, this may be explained by the absence of a cement interface on the integrated crowns.

A Photoelastic Stress Analysis of Fixed Partial Dentures with Bicon Implants on Mandibular Posterior Area

Korean Acad Prosthodont. | August, 2004
Kang, JU., Kim, NY., Kim, YL., and Cho, HW.

Statement of Problem: Several prosthetic options are available for the restoration of multiple adjacent implants. A passively fitting prosthesis has been considered a prerequisite for the success and maintenance of osseointegration. Passivity is a particular concern with multiple implants because of documented inaccuracies in the casting and soldering process. One way to avoid this problem is to restore the implants individually, however, the restorations of individual adjacent impants requires careful adjustment of interproximal contacts.
PURPOSE: The purpose of this study was to compare the stress distribution pattern and amount surrounding Bicon implants with individual crowns and splinted restorations.
Material and Methods: A photoelastic model of a human partially edentulous left mandible with 3 Bicon implants(4*1 mm) was fabricated. For non-splinted restorations, individual crowns were fabricated on 3 abutments (4.0*6.5 mm, 0 degree, 2.0 mm post, Bicon Inc., Boston, USA) After the units were cemented, 4 levels of interproximal contact tightness were evaluated: open, ideal (8 micrometershim stock drags without tearing), medium(40 micrometer), and heavy(80 micrometer). Splinted 3-unit fixed partial dentures were fabricated and cemented to the model. Changes in stress distribution under simulated non-loaded and loaded conditions(7.5, 15, 30 lb) were analyzed with a circular polaricope.
Results: 1. Stresses were distributed around the entire body of fin in Bicon implants. 2. Splinted restorations were useful for distribution of stress around implants especially with higher loads. 3. By increasing the contact tightness between the individually restored three implants, the stress increased in the coronal portion of implants.
ConclusionsS: Ideal adjustment of the contact tightness was important to reduce the stresses around individually restored Bicon implants.

Biomechanical Evaluation of a Wide Diameter Bicon Dental Implant in Various Bone Conditions

AO Annual Meeting | San Francisco, CA | March, 2004
Bozkaya, D., Muftu, S. and Muftu, A.

An association between higher implant failure rates and regions of poor bone density, commonly found in the posterior maxilla and mandible, has been reported in the literature. Moreover, implant placement in posterior regions is often limited by anatomic changes due to edentulism, where implant design alteration may be an alternative for treatment planning. In this regard, using a short implant with a large diameter in anatomically compromised regions may provide further increase in implant stability and long-term clinical success. The purpose of this study was to evaluate the biomechanical response of the bone for a wide and short implant, (WSI) (6 mm in diameter x 5.7 mm in length) versus a narrow and long implant (NLI) (3.5 mm x 11 mm) in various bone densities through finite element analyses (FEA). Both implants are using Bicon Morse-taper and made of Ti-6AL-4V. The implants and their respective bone domains were graphically designed through 3-D CAD software. After mesh refinement, different cortical to trabecular ratios and elastic moduli were assigned to the bone domain's elements to reproduce various bone conditions (Types II-IV). Vertical and horizontal loads were applied to the top of the Morse-taper connected abutments of the two implants. Implant and bone stress and strain states were evaluated numerically for analysis. The results showed that the implants presented comparable strain distributions under vertical loads and that the WSI presented lower strain values when the horizontal load was considered. The stress invariant values were also lower for the WSI implant. Increased stress and strain values were found at lower bone densities, where these values were higher for the NLI in most cases. According to the results obtained by this computer-based analysis, it can be concluded that the WSI implant presented an overall better biomechanical force distribution than the NLI when horizontal forces were applied for the different bone densities analyzed and may be considered for implantation of anatomically compromised regions and regions of poor bone quality.

Bacterial Adhesion on Integrated Abutment Crowns™. In Vivo Study (II)

IADR/AADR/CADR 80th General Session | Honolulu, HI | March, 2004
M. MARINCOLA, S. DIBART, M.L. WARBINGTON, Z. SKOBE, R. URDANETA, and S.-K. CHUANG, University of Cartagena, AISI, Italian Association of Restorative Implant Dentistry, Rome, Italy, Boston University, MA, USA, Forsyth Institute, Boston, MA, Harvard University, Concord Dental Associates, Concord, MA, USA, Massachusetts General Hospital and Harvard School of Dental Medicine, Harvard School of Public Health, Chestnut Hill. IADR/AADR/CADR 80th General Session; Honolulu, HI

Objectives: The purpose of this study was to compare the subgingival microbiota present on implant supported Integrated Abutment Crowns (IAC) and natural teeth in vivo.

Material and Methods: A cross-sectional study design was utilized with patients selected from the patient pool at the Implant Dentistry Centre at Faulkner Hospital (Boston, MA). Thirty-one patients (13 males and 18 females) were selected, mean age 57.36 years (range 28.09 to 90.85 years) of which 4 were smokers. Selection requirements were: Patients had IAC crowns placed at least 6 months ago and had not taken antibiotics 3 months prior evaluation. Gingival index (GI), modified bleeding index (MBI), subgingival plaque samples and clinical photographs were taken on at least 1 IAC and the natural contralateral tooth on each patient. The subgingival plaque samples were taken from the mesial side of the IAC or natural teeth and put in an Eppendorf tube containing 0.150 ml Tris-EDTA. The samples were then hybridized with 12 whole chromosomal probes to Tannerella forsythensis, Prevotella intermedia, Campylobacter rectus, Fusobacterium nucleatum, Actinomyes odontolyticus, Streptococcus sanguis, Streptococcus intermedius, Actinobacillus actinomycetemcomitans serotype b, Actinomyces naeslundii, Streptococcus oralis, Porphyromonas gingivalis and Prevotella intermedia , using the checkerboard DNA-DNA hybridization method. The descriptive statistics and generalized linear mixed models (GLMM) accounted for intra-cluster correlation within the same patient were utilized using SAS-PC (version 8.2, 2001) Results: IAC were noted to have less GI and MBI compared with natural teeth but were not statistically significant (p>0.05). There were no statistical differences (p>0.05) in all the various colonies count between IAC and the natural teeth.

Conclusions: The IAC showed striking similarities with the natural tooth in terms of subgingival bacteria plaque count and composition. The IAC also showed lower GI and MBI indices.

Supported by a research grant from Bicon (MM, SD), OMSF Foundation Fellowship in Clinical Investigation (SKC).

Bacterial Adhesion on Integrated Abutment Crowns™. In Vitro Study (I)

IADR/AADR/CADR 80th General Session | Honolulu, HI | March, 2004
S. DIBART, M. MARINCOLA, M.L. WARBINGTON, and Z. SKOBE, Boston University, MA, USA, University of Cartagena, AISI, Italian Association of Restorative Implant Dentistry, Rome, Italy, Forsyth Institute, Boston, MA.

Objectives: The goal of the present investigation was to determine if the DiamondCrown material, used to make Bicon's Integrated Abutment Crown (IAC), is less susceptible to harbor/attract bacterial plaque than All Ceramic (AC) or Metal Ceramic (MC) crowns. A secondary goal was to compare the composition of the plaque attracted on tested surfaces.

Methods: 6 IAC, 6 AC and 6 MC crowns were equally divided in 2 test groups. The AC and MC crowns were cemented on titanium abutments. Group I (3 IAC,3 AC, 3 MC) and group II were incubated for 10 min in a bacterial solution containing 10 different oral bacteria at O.D.1: Tanerella forsythensis, Prevotella intermedia, Campylobacter rectus, Fusobacterium nucleatum, Actinomyces odontololyticus, Streptococcus intermedius, Actinobacillus actinomycetemcomitans serotype b, Actinomyces naeslundii, Streptococcus oralis, Porphyromonas gingivalis. After a brief wash in PBS to eliminate the unbound plaque, the crown samples in group I were incubated in 500µl of Tris-EDTA buffer with 500µl of NaOH. The samples were then hybridized with 10 whole chromosomal probes to the above mentioned microorganisms. The microbiological analysis was completed using the checkerboard DNA-DNA hybridization method. The samples in group II were briefly washed in PBS and fixed in 4% formalin for scanning electron microscopy (SEM).

Results: All experimental crowns showed bacterial adhesion. There was no statistical difference in the microbial compositions when comparing crowns. The SEM showed that the AC crowns were harboring the heaviest bacterial deposits. MC and IAC showed the least bacterial deposits especially at the abutment/crown interface.

Conclusions: The IAC and MC crowns appear to be less prone to bacterial colonization, in an in vitro setting then an all ceramic crown. IAC and MC crowns harbored very few bacteria at the abutment/crown interface.

This study was supported by a research grant from Bicon.

Two-Year Retrospective Evaluation of a Unique Restoration for Single Implants

IADR/AADR/CADR 80th General Session | Honolulu, HI | March, 2004
R. URDANETA, Harvard University, Concord Dental Associates, Concord, MA, USA, M. MARINCOLA, University of Cartagena, AISI, Italian Association of Restorative Implant Dentistry, Rome, Italy, and S.-K. CHUANG, Massachusetts General Hospital and Harvard School of Dental Medicine, Harvard School of Public Health, Chestnut Hill.

The Integrated Abutment Crown™ (IAC) (Bicon, Boston, MA) is a technique for the fabrication of single-tooth implant-supported restorations where the abutment and the crown material are one integral unit without the use of any screws or cement.

Objectives: The objective of this study was to examine the 2-year clinical performance of 151 IACs placed in a general dental practice.

Materials and Methods: A retrospective cohort study design was utilized with patients selected from the patient pool at the Implant Dentistry Centre at Faulkner Hospital (Boston, MA). Patients were recalled and the restorations were evaluated following the modified USPHS criteria. The gingival esthetics and the number of restorative appointments were documented. Descriptive statistics and generalized linear mixed models (GLMM) accounting for intra-cluster correlation within the same patient were utilized using SAS-PC (version 8.2, 2001).

Results: A total of 151 implants were restored with IACs on 59 patients, with a mean age of 58.2 years, 62% were placed in the maxilla and 38% placed in the mandible. The 2-year survival rate for IACs was 98.56%. Two IACs were removed, one due to implant failure; all others were rated as either excellent or good for anatomy, surface texture, and color. No IACs were removed due to fractures. Excellent marginal adaptation was observed with no clinically discernible interface between the veneer material and the abutment. Excellent gingival esthetics was observed. Significantly fewer appointments were needed to restore an IAC than a PFM (p<.0001).

Conclusion: The results of this prosthetic evaluation supported the conclusion that the Integrated Abutment Crown™ is an excellent choice for the restoration of locking-taper single implants for both anterior and posterior areas of the mouth. IACs are a cost-effective and timesaving alternative to PFMs.

Supported by Oral and Maxillofacial Surgery Foundation (OMSF) Fellowship in Clinical Investigation (SKC).

Biomechanical Assessment of an IBAD Surface-Modified Implant

IADR/AADR/CADR 80th General Session | Honolulu, HI | March, 2004
P.G. COELHO, University of Alabama at Birmingham, Birmingam, USA, J. LEMONS, University of Alabama at Birmingham, USA, and A.W. EBERHARDT, University of Alabama at Birmingham, USA.

Attention has been given by implantology research groups regarding thin-film bioceramic coatings on dental implants due to the potential controlled coating dissolution/biological degradation after implantation and direct bone anchorage to the metallic substrate.

Objective: The purpose of this study was to evaluate the biological fixation of a thin-film ion beam assisted deposition (IBAD) surface-modified implant versus a non-surface-modified titanium alloy implant at early implantation times in-vivo in a laboratory canine model.

Methods: The implants were placed in the dogs’ tibiae and remained for 2 and 4 weeks in vivo. After euthanization, the limbs were retrieved and reduced to blocks containing the implant in its center. The blocks were mounted in epoxy resin and the implants were pulled-out at 0.5 in/min in a universal testing machine. Force versus displacement curves were recorded for the specimens, which were subsequently decalcified and prepared (H. and E. stain) for histomorphometric assessment of bone contact at the implant surface enabling interfacial shear stress calculations.

Results: The results showed that bone contact at the implant surface was significantly higher (P<0.03) for the non-surface-modified when compared to surface-modified implants for both times in vivo, and that the pullout forces were not statistically different among the four groups. ANOVA revealed that time in-vivo and surface treatment did not affect interfacial shear stress.

Conclusion: According to the histomorphometric and biomechanical results obtained in this study, it was concluded that there were no weak links between the thin-film coating and the metallic substrate. Furthermore, the bone around the surface-modified implants may have improved mechanical properties, which is a desirable feature for early and long-term implantation of load bearing devices. These results suggest that total dissolution/biological degradation of the coating may not be complete at these early implantation times.

Radial Implant-Abutment Gap Determination Through Serial-Sectioning Method

IADR/AADR/CADR 80th General Session | Honolulu, HI | March, 2004
P.G. COELHO, University of Alabama at Birmingham, Birmingham, USA, M. SUZUKI, University of Alabama at Birmingham, USA, and A.L. COELHO, UNICENP, Curitiba, Brazil.

Significant attention has been devoted by the implantology and bioengineering research community regarding the implant-abutment gap, once such gap may provide a favorable environment for bacterial adhesion/proliferation and to degradation of the metallic substrate. Classically, this distance has been evaluated by means of scanning electron microscopy (SEM) along the implant perimeter and no information is revealed as a function of radius.

Objective: The purpose of this study was to evaluate the implant-abutment gap as a function of radius by means of optical microscopy evaluation through a sequential sectioning technique.

Methods: Six implants (3.75 mm in diameter) and abutments were screw connected and torqued to 20 N.cm. Outer radius measurements were recorded by SEM. The implants were then mounted in epoxy resin using a metallic fixture to assure implant position (perpendicular to the vertical axis). Subsequently, each implant was abraded and polished parallel to its long axis at six different distance intervals. Implant-abutment gaps were obtained by optical microscopy (1000X mag.) and these distances were related to its radial position through trigonometric inferences. A 6th degree polynomial best line fit approach was used to determine the radial adaptation patterns for each of the implants.

Results: The results showed that gap distances were not statistically different among the implants (P=0.05). The polynomial best line fit approach revealed that the implant-abutment gap distance increases as a function of implant radius and this increase is more pronounced in the outer 1⁄4 radius, at the abutment beveled region. Also, communication between external and internal regions of the implant were found for all specimens.

Conclusion: Based on these results, it was concluded that this methodology provided a broader scenario of the implant-abutment gap distance and that SEM evaluations may underestimate the gap value.

Use of Integrated Abutment Crowns to Enhance the Aesthetics of Maxillary Anterior Implant Restorations

AO General Session | San Francisco, CA | March, 2004
Leary, J., Hirayama, M.

Achieving excellent aesthetics with maxillary anterior implant restorations is challenging to even the most accomplished clinicians. Placing implants in the area of the mouth is not only a clinically demanding task but often involves unrealistic patient expectations.

The cases presented here utilize an Integrated Abutment CrownsTM(IAC), an innovative technique in implant prosthetics, to achieve aesthetic restorations in a narrow edentulous space. These cases also demonstrate a multi-disciplined approach solving the problem of esthetics in the maxillary anterior. Orthodontic tooth movement , periodontal plastic surgery, and immediate stabilization have been used to achieve the desired clinical results.

This presentation should add to our ability to enhance anterior aesthetics in even the most demanding situation.

Risk Factors with Radiographic Bone Loss in Dental Implants in a Five-Year Retrospecitve Cohort Study

AO General Session | San Francisco, CA | March, 2004
Chuang, S.K.

Objectives: The purpose of this study was to examine the long-term follow-up (> 5 years) of radiographic evaluation of Bicon dental implants and the risk factors associated with radiographic bone loss beyond the first thread placed at the Implant Dentistry Center (IDC) in Boston, Massachusetts.

Materials and Methods: To address the research purpose, a retrospective cohort study design was used. The cohort was composed of patients who had at least one Bicon dental implant placed for 5 years and were willing to return to IDC for the 5 year follow-up radiographic examination of these originally placed implants. Risk factors were categorized as demographic, implant-specific and anatomic variables. The outcome variable as failure was bone loss beyond the first implant thread on either the mesial or the distal aspects of the implant. Risk factors for bone loss were identified using the generalized estimating equations (GEE) approach adjusted for clustered implant observations within the same patient.

Results: There were 50 patients with 117 implants with a mean age of 50.75 years (range: 17.61 to 82.84 years) of which 26 were females. There were 52 implants placed in the maxilla and 65 implants in the mandible. On the mesial side, 6 implants (5.13%) lost bone beyond the first thread over 5 years. On the distal side, 5 implants (4.27%) lost bone beyond the first thread over the five years. A total of 6 implants (5.13%) had lost bone beyond the first thread on at least the mesial or the distal aspect. Risk factors associated with bone loss beyond the first thread (p < 0.20) included age at implant placement, quality of bone, and implant length. Based on the adjusted multivariate GEE model including gender for biologic importance, risk factors associated with bone loss beyond the first thread was age at implant placement (odds ratio =1.14, p =0.04).

Conclusions: The results of this long-term follow-up radiographic study supported the fact that the Bicon dental implant system is an excellent choice for the prosthetic restoration of the locking-taper implant design. We identified one risk factor (age at implant placement) associated with bone loss beyond the first thread. This key factor is not under the direct control of the practitioner. Supported by Oral and Maxillofacial Surgery (OMSF) Fellowship in Clinical Investigation (SKC).

Immediate Stabilization and Functioning: Anterior Aesthetics

WCOI General Session | Honolulu, HI | March, 2004
Leary, J., Hirayama, M.

The immediate stabilization and loading has become one of the more prominent topics in implant dentistry today. Clinical testing by clinicians, engineering improvements from manufacturers, and patient demand have allowed clinicians to reduce the osseointegration healing period from a conservative time of 6-9 months to period of 1-3 months. Many practitioners acknowledge and utilize the immediate stabilization and functioning: however, a majority of clinicians are still skeptical about such methods and techniques. This presentation shall show step by step methodology of totally chair-side technique of immediate stabilization and functioning with two year retrospective study.

In this retrospective clinical study, 477 fin-type implants (Hydroxyappatite coated, Titanium Plasma Spray, or Uncoated) in 208 patients during the periods from July 1, 2001 unlit July 31, 2003. All implants are immediately stabilized and functioned by fabrication of temporary prosthesis by bonding the prosthesis to remaining teeth or splinting one piece prosthesis for full arch cases.

Further to the normal principles of implant placement the immediate stabilization technique requires only one criterion. That is the ability to prosthetically immobilize the implant with a transitional stabilization prosthesis. Successful osseointegration is not dependent upon the density or quality of the bone to provide initial stability of the implant in its osteotomy. Implants placed immediately after an extraction or even a ridge split osteotomy are excellent candidates for the immediate stabilization or (immediate) loading technique. This technique is applicable for a single implant or for a full arch of implants.

With this new concept and fully chair-side technique shown in this presentation, a clinician can provide an immediately stabilized and immediately functioned prosthesis on the same day as implant placement giving the patient both function and aesthetics. Based upon these clinical evidence, the immediately stabilized and functioned implant technique is a viable treatment option that should be part of every implant practice.

Immediate Loading Implants for Overdentures

AO General Session | San Francisco, CA | March, 2004
Speratti, D.

The immediate loading of implants has become a prominent topic in implant dentistry lately. Engineering improvements from manufacturers and clinical testing have allowed clinicians to offer immediately loaded implants to a wider patient population. The application of this technique for over dentures is a rewarding treatment for both dentists and patients. Patients benefit from gaining immediate prosthetic stability in a cost effective manner and clinicians by being able to offer an efficient and predictable treatment that improves many patients quality of life.

Efficiency Considerations for the Purely Tapered Interference Fit (TIF) Abutments Used in Dental Implants

Journal of Biomechanical Engineering, Trans ASME
Bozkaya, D., Müftü, S. and Müftü, A.

A tapered interference fit provides a mechanically reliable retention mechanism for the implant-abutment interface in a dental implant. Understanding the mechanical properties of the tapered interface with or without a screw at the bottom has been the subject of a considerable amount of studies involving experiments and finite element (FE) analysis. In this paper, approximate closed-form formulas are developed to analyze the mechanics of a tapered interference fit. In particular the insertion force, the efficiency, defined as the ratio of the pull-out force to insertion force, and the critical insertion depth, which causes the onset of plastic deformation, are analyzed. It is shown that the insertion force is a function of the taper angle, the contact length, the inner and outer radii of the implant, the static and the kinetic coefficients of friction, and the elastic modul of the implant/abutment materials. The efficiency of the tapered interference fit, which is defined as the ratio of the pull-out force to insertion force, is found to be greater than one, for taper angles that are less than 6o when the friction coefficient is 0.3. A safe range of insertion forces has been shown to exist. The lower end of this range depends on the maximum pull-out force that may occur due to occlusion in the multiple tooth restorations and the efficiency of the system; and the upper end of this range depends on the plastic deformation of the abutment and the implant due to interference fit. It has been shown that using a small taper angle and a long contact length widens the safe range of insertion forces.

Immediate Loaded implants: How clinicians can achieve aesthetic results

AAID General Session | Hollywood, FL | November, 2003
Hirayama, M., Wang, M.

The “immediate loading” technique has become a popular procedure in implant dentistry. Some practitioners use this method routinely while many remain skeptical about this treatment. The purpose of this study is to demonstrate that the immediate loading technique is a viable and practical treatment option.

Our clinical methodology of “immediate loading” and its concept will be explained in this presentation. Preservation of hard and soft tissue around the implant site is the most critical issue in aesthetic implant dentistry. Clinicians can utilize these methods for many types of cases while providing an immediate temporary restoration on same day implant placement.

Bone Levels around Immediately Loaded-Stabilized Vs. Conventionally loaded locking-taper implants

AAID General Session | Hollywood, FL | November, 2003
Hirayama, M., Urdaneta, R.

Synopsis: Once an implant is uncovered, vertical bone loss of 1.5-2.0mm is observed apically from the newly established implant-abutment interface. This has been well documented for screw-type implant abutment connections.

The purpose of this study was to evaluate bone loss around a locking taper implant-abutment connection interface in immediately loaded and conventionally loaded one and two stage implants. The following objectives will be discussed in this presentation as a retrospective analysis: factors affecting peri-implant tissue conditions; assessment of peri-implant bone levels around immediately loaded vs. conventionally loaded implants; remodeling of peri-implant bone after functional loading; and changes in crestal bone levels during the first year after functional loading.

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Mechanics of the tapered interference fit in dental implants

Journal of Biomechanics, Vol. 36, No. 11, pp. 1649-1658
D. Bozkaya and S. Müftü

In evaluation of the long-term success of a dental implant, the reliability and the stability of the implant-abutment interface plays a great role. Tapered interference fits provide a reliable connection method between the abutment and the implant. In this work, the mechanics of the tapered interference fits were analyzed using a closed-form formula and the finite element (FE) method. An analytical solution, which is used to predict the contact pressure in a straight interference, was modified to predict the contact pressure in the tapered implant-abutment interface. Elastic-plastic FE analysis was used to simulate the implant and abutment material behavior. The validity and the applicability of the analytical solution were investigated by comparisons with the FE model for a range of problem parameters. It was shown that the analytical solution could be used to determine the pull-out force and loosening-torque with 5-10% error. Detailed analysis of the stress distribution due to tapered interference fit, in a commercially available, abutment-implant system was carried out. This analysis shows that plastic deformation in the implant limits the increase in the pull-out force that would have been otherwise predicted by higher interference values.

Determination of Bone Activity around a Surface-modified Titanium Alloy Implant

AADR/CADR Annual Meeting | San Antonio, TX | June, 2003
P.G. COELHO, University of Alabama at Birmingham, USA, and J. LEMONS, University of Alabama at Birmingham, USA.

Objective: The purpose of this study was to evaluate the cortical and trabecular