The Bicon Design: Offering Unique Clinical Capabilities

I’m now, in turn, going to introduce Bob Chapman who is a prosthodontist. He’s the chairman of the department of prosthodontics and operative dentistry at Tufts. He’s the cofounder of the dental implant center at Tufts, and he introduced Vin Morgan to the Stryker implant in nineteen ninety two. Bob. Thank you, Geoff. My presentation is going to be on the design and its ability to offer unique clinical capabilities. The capabilities that I’ve always liked in the Bicon implant are three. It’s reliable osseointegration and the maintenance of that osseointegration. The reliable abutment connector and its uniqueness. And its versatility because of the uniqueness of the connector. This is a patient that I had been very concerned about when I first started seeing her. She was a heavy clencher. Plaque control wasn’t very good. She had a lot of root canals. Every time she had a root canal and a crown made, she would break the crown or break the root. So when she started losing many teeth, she was referred to me, and I didn’t know, frankly know what to do. But I’d started using the Stryker implant at the time and had been using it about five years, and I said, well, I’m a fairly conservative person when it comes to dentistry. I said, well, me give it, let me give this a chance. So Norm Shepherd did a sinus augmentation. We put in three implants, and then I said, well, maybe we’ll give it a chance because the forces are going to be longitudinal straight down the long axis of the tooth, or the implant. And let’s see if we can put in some individual crowns. So we did, and this is eight years later now. And she’s had absolutely no problems. Nothing is fractured, nothing has come loose. She’s, her plaque control still isn’t the greatest in the world. But the aesthetics and the health of the tissues are still superb. And we’ll talk about a little bit about why that health, I think, of the tissues is so good. So my experience has been right from the beginning very good, but it’s been that positive experience that I’ve had has been continually, I’m continually impressed by the results that I get. The reason I think we are getting such good results from the implant itself is because of its unique the uniqueness of design. And Jack Lemmons, who’s a marvelous researcher and has been for many years, is going to go into this in more detail. But just let me say that one of the reasons perhaps that the osseointegration is so good with this implant and its maintenance is so reliable, is because of how the design distributes stresses, and how its design also provides for good blood supply. In between the plateaus of this implant, because of its spacing between the plateaus or its fins, is sufficient space, so Haversian canal systems within the bone can be re modified, redeveloped on a continual basis. And bone, in order for it to be maintained, has got to modify itself over time. So this may be one of the reasons why the implant is so successful, and Jack will talk about this in more detail. The implants also, as Vin just mentioned, are capable of modification from their basic design probably because of the basic design. Whether it’s a narrow implant like the three point five millimeter implant, or a wide implant like the six millimeter implant. The stress distribution is unique and I think is one of the reasons why the osseointegration occurs very, very well and its success rate is very high. And also why bone is maintained very well, not only because of its plateau design, but because of that sloping shoulder design. If you notice post insertion after eight years, even though the radiograph is taken from a different angle, bone is at least maintained, if not bone growing along the surface of the implant. This is a horizontal stress analysis of the three point five millimeter implant and the six millimeter implant. And although in the narrower diameter implant, the stresses are more concentrated near the top of the implant, in both cases stress is continual around the implant. The yellow and the greenish or the lighter colors are where stress is being concentrated. As far as vertical load is concerned, the vertical load on the implants is very, very similar. Interestingly enough though, on the shorter implants, there’s greater stress concentrated around the inferior portion or the bottom of the shorter implant. Most of the time, concentrates around the top of the implant. But with the sloping shoulder and with the plateauing design, stress distribution actually is maintaining and probably enhancing bone development. Here’s a couple of cases. At the top, this was immediate placement and loading of two implants, and single tooth, or single tooth, single restoration implants, not splinted together. The top slide on the left is at insertion, and the bottom slide on the left is thirty months post op. You can see where bone is actually developed along the surface of the implant, and actually seems to have been growing along the surface of the implant. And this implant, as you may have noticed from some of the previous slides, has really not been modified in its surface texture over time. So the surface texture per se is probably not the reason why the implant is that successful. It has to do with its macro mechanical design, the actual shapes that have been developed. And again, on the right side of your screen, you can see again immediate load on insertion. And the bone is not around the sloping shoulder, the top of the sloping shoulder. But on the bottom part of the screen you can see where bone is growing up to the surface of the implant. So I think the design of the implant is extremely important. The design is also important in providing for what patients really are looking for, particularly today. And that is reliable aesthetics. This is a patient of mine that had come in with a three unit bridge that had chipped, replacing, actually replacing number six. But in fact, number six had been orthodontically moved into a congenital missing number seven area. But the aesthetics was just not good. She didn’t like the idea that she had a bridge. She wanted an implant. And I said, okay, we can do that for you. So we put an implant in the number six area. We had decided to restore this as a single crown obviously. And one of the things that I think it’s important to look at is how good that tissue looks, how much it looks like actual gingival tissue, even though it’s mucosal tissue. As you’ll be hearing from Bill Grippo and Bert Balkin and others, the tissue surrounding implants is not gingival tissue. It’s mucosal tissue with a heavy band of connective tissue. And in this particular patient, the aesthetics is based upon the fact that that gingival tissue is maintained in place first by the thick band of connective tissue surrounding the post underneath the inferior rounded abutment, and the fact that bone is maintained around the sloping shoulder. So it’s the maintenance of the bone around the sloping shoulder, and the uniqueness, design of the abutment connector that provides for such good aesthetics. Now this has been in here for about eight years, the five years, I’m sorry, and the patient has been extremely happy. And so have I, obviously. As far as the abutment connection is concerned, one of the things about this abutment connector is not only the reliability of the aesthetics that you get because of the great gingival tissue response, or mucosal tissue I should say response. But also the reliability and the flexibility of the attachment mechanism of the abutment to the implant itself. Retention of an abutment connector really is two phase. One is the retention itself per se, the other is the stabilization for that retention. And retention is either with screws in most implant systems or a locking taper unique to the BiCon implant system. Stabilization of the connector provides its reliability, I. E. If it’s not stable, it’s going to loosen. And there are different ways of stabilizing a connector. One is with a hex, whether it’s internal or external, and I’m using hex in a generic way. There are hex by design, but there are also hex analogs, that is various shapes, either external or internal to the implant, that help reduce the movement of the screw or the tendency for the screw to loosen. These hexes or stabilizing devices can be internal or external. But there are also two other types of stabilizing designs. One is the locking taper and the other is the releasing taper. Now the difference between a locking taper and a releasing taper is that a locking taper is less than four degrees inclusive. That means that the taper on one side and the taper on the other side added together are called the inclusive taper. And a locking taper has to be less than four degrees in order for it to lock into place. A releasing taper on the other hand is anything greater than four degrees. And actually a releasing taper acts like a wedge. It is a stabilizing device, but needs a screw to prevent the wedge from releasing itself or popping out. One of the ways to look at it is when you tap a wedge into something, it’ll actually bounce back. And you really need that screw to help retain the releasing taper, but by the same token, a releasing taper can actually help stabilize the screw. So it’s a mechanism that actually works fairly well. On the left hand side of your screen, you see the locking taper. In the center is a hex implant, an external hex, not an internal hex. And then on the right hand side of the screen are two releasing taper designs. They all work, but the more reliable attachment mechanism is the locking taper. And there are a number of people, one fairly well known developer of an implant that I was talking to last year, and we were talking about different attachment mechanisms. And I said, do you ever think about when you were designing the implant, talking about using a locking taper? And he said, no, he said, but I’m thinking about it now. So there are a number of people around in the business, and all of these companies are in competition. And they all like to pick and choose from their competitors that which is best. And many people are looking at, hear me Vin, many people are looking at the locking taper design as one of the things that they’re going to try and pick off. So the locking taper design is not only unique because of its reliability, but because it is circular, three sixty degrees, it provides tremendous versatility for how that abutment can be placed with angled heads on it. So it gives you the most flexibility for the aesthetics or the placement for comfort of the implant, or for the prosthetics on the implant. Retention at any interface, whether it’s a screw or a locking taper, requires friction. Now friction is essentially intimate contact between two surfaces. And the way that things are held together, whether it’s a screw holding two pieces of metal together, or whether it’s a nail holding a board to another board, it means that there are little bumps on the two surfaces that interact with each other. These bumps are called asparities, and they slide over each other and lock into place. And they’re microscopic, most of the time you can’t see them. If you look at a surface and it looks a little bit dull, that means that it’s got some bumps on it because light is reflected different ways from the bumps. And almost every surface, even if it’s shiny, has some bumps to it. So when you place a locking taper with these almost parallel surfaces and tap into place, it’s like tapping a nail in. And all of these little bumps slide over each other and then rest into place. And the tapping in is providing momentum and inertia, and that means that once that is in place, all that energy that has been put into the system to put it in place, now is contained within the two components, the nail and the board, or the screw and the tap, or in this case a locking taper in its well. And it takes an equal or really greater amount of force to separate the two. And this is what these look like. These slides are courtesy of Ken Keating at Dublin University who’s done a good bit of work on the locking taper. And you can see on the right hand side of that slide, that blow up of that rectangle, just what these two surfaces look like. They’re slightly irregular, but they are in intimate contact, almost a hundred percent contact between the two components, or very close in approximation. It’s actually point five microns or less. And this intimate contact is what prevents any movement of the two pieces vis-à-vis one another. When you look at a close-up photograph of the abutment itself, you can see almost little circular rings. Those little circular rings are formed by the manufacturing process, the CAD/CAM ing process. And you have rings, microscopic rings on the abutment post, as well as corresponding rings within the body of the implant itself, within the well of the implant. And when you tap these two things together, these little grooves or rings bump around each other, flex around each other, and then come to rest, and that’s what holds it all together. And yet, you can take it apart when you need to. So this is a unique design and a very, very reliable design. And one of the reasons why I was intrigued by this implant when I first heard Tom Driscoll talk about it in Florida somewhere around fifteen years ago. And that’s why I said to Vin, this is something you should think about. Because the major implant design at the time had a hex top, which was not particularly a good mechanism for stabilizing the screw. And the screws also developed a lot of bacteria around them. Many of us who, and any of you guys who have been around for a long time who have taken some of the old prostheses apart that are screw retained, the odor is rather objectionable. And that’s because there’s a flux of bacteria in and out of the implant. Van Steenbergher in Belgium has done a good bit of work on this. Now, is this a problem? Well, at the lower part of the slide, are actually some screws that had been in another implant design that I had to take apart because the bar broke. And when I looked in there, said gee, did this person cement these screws in? And then I realized that it wasn’t cement, it was calculus. So sooner or later, you’re probably going to get calcification of the bacteria that are in there. Nonetheless, this did not have a great odor on it when I took it apart. So when we’re looking at designs that provide not only good retention, we also look at the biologic side of it. And that is that there are always gaps between a screw thread and a tap. And that’s where bacteria are going to get involved and they’re going to multiply and they’re going to stay around there for a long time. Now does this have anything to do with osseointegration? It may or it may not. Serge Dibart, who is going to be speaking I think tomorrow, or I believe it’s tomorrow, will go into this in more detail. But one of the aspects of any system that has got access to the oral cavity means that we’re going have bacteria. And these bacteria have to be thought about in terms of what they might do, particularly to the immediate load situation. Is bone maintained around the top of the Bicon implant because of its sloping shoulder? Or is it maintained in part because of the sloping shoulder design with stress distribution that’s appropriate? And do bacteria play any role in this? Very, very difficult to know because there hasn’t been an awful lot of research done in this by anybody. But, I would, venture to guess that bacteria do play some role, at the very least, in the healthy looking mucosal tissue that simulates gingival health around the Bicon implant.