Boston University
Clinical Director, Post Doctoral Periodontology
Can I now introduce Serge Dibart who’s a periodontist? He’s an associate professor and clinical instructor at the Boston University of Dental Medicine. He’s a clinical professor at the Forsyth School of Prudential Hygienists, and he’s in private practice in Watertown, Massachusetts. Serge. Thank you. Thank you, Mr. Chairman. Ladies and gentlemen, good afternoon. I would like to thank Bicon for giving me this opportunity to come and speak at the World Symposium today and share with you the result of some of the research we did about a couple of years ago. It was aimed at assessing the bacterial seal that’s provided by the Bicon implant abutment connection. And why is that important? Well, what happens when you place an implant? It’s like being married to the patient, really. And liking good things, like you have a good marriage, then things are fine, or it can become ugly very, very quickly. And what do I mean by that? You have implant failures. Now, this is taken from Dave Cochran’s review paper in the Journal of Periodontology of nineteen ninety six. The two main causes of late implant failures are mechanical or bacterial. Mechanical, as you can see here on the left hand side, it’s due to occlusal overload or defective parts of the implant. The result is that you need to go back because you have an implant that is now broken below the bone level, and try to retrieve that with a trephine. Most common are the implant failures due to bacterial infection. In that case, here not only you have a loss of the implant, but you also have a loss of bone surrounding the implant, making things much more complicated. And indeed, the bacterial factor is something that we have to be reckoned with. What you see here, ladies and gentlemen, is agar plate with some periodontal pathogens on it. Those pathogens will affect the teeth, this rat model here as you can see, and these pathogens will just destroy the bone around natural teeth, and we call that periodontitis. When these pathogens affect the bone surrounding the implant, we have a situation that we call peri implantitis. In both cases, the outcome is the same. You have the loss of the implant and the loss of tooth, with the added annoyance that for the implant, the patient had paid for the implant. As we say here in America, the first two sets of teeth are given to you by God for free, the third one, you have to pay us. And it’s very annoying when they come with this, you know, and it can create problems. Now, what happens when you have submerged implants or two stage implants, you have a portion of the abutment that is connected to the body of the implant. And sometimes you have something that’s called the micro gap, as you can see here. Now the microgap is an opening between the abutment and the implant, and as with every opening, you have a space that invites colonization, colonization of bacteria that are in the oral cavity. These bacteria can, very cleverly, go into the implant well. And at that point, what you have is really a reservoir, a reservoir of bacteria that is inside the implant. At that point, it really doesn’t matter how many hours a day the patient brushes, how many gallons of Peridex rinses, or how many pounds of antibiotics it takes, nothing is going to affect the bacteria that are hidden into the implant well here. These clever organisms can then leak out from this well into the environment. And what we have then is a cascade of events: chronic inflammation, activation of the osteoclast, and finally bone loss. A few rounds of these and you have an enormous amount of bone loss around the implants. A few years ago, two years ago, the people at Bicon came to see us and asked us to test their implant abutment connection. They wanted to know how their implant abutment connection with that locking taper design will stand up to the bacterial challenge. So how do we test for this bacterial seal of the Bicon implant? We devised a two phase experiment. The first phase we call the outside in phase. What we did, we took the abutment, put it on the implant in a sterile fashion, and then put this implant abutment unit into a bacterial broth and see if the bacteria were invading the implant space. The second experiment we called inside out, because we purposefully put some bacteria into the implant well, closed it with the abutment, and then put that unit into a sterile broth to see if the bacteria were able to leak outside of the abutment. So again, phase one, to test the ability of the seal to shield the implant well from the outside bacteria, and the phase two experiment was to test the ability of the seal to prevent bacteria present in the implant well to seep out. In the phase one experiment we used ten wide body Bicon implants and abutments. Five x eleven millimeters uncoated implants with three millimeters wells, five by six point five millimeter abutment with three millimeter posts. Those were assembled according to the manufacturer’s guideline under sterile condition. We worked under a sterile cell culture hood, so there would be no contamination whatsoever. Once these implant abutment units were assembled, they were immersed in the bacterial broth for twenty four hours. And this is the bacterial broth. We chose our bacteria very, very carefully. We wanted to have bacteria that will be oral bacteria, anaerobic or facultative anaerobic bacteria, because that’s what you find in the mouth as pathogens. And the sizes also were chosen very, very careful, and there was a reason for that. We had small, medium, and large. Now, Actinobacillus actinomycetemcomitans, is a well known periodontal pathogens. It’s also one of the smallest pathogens that we know of. The diameter is point five micron. We selected Streptococcus oralis, it’s a medium sized bacteria, about two microns in diameter. And finally, we selected a big one, what we call big microbiologists, it’s like ten microns. Fusobacterium nucleatum subspecies vincentii. On the left hand side here, you see how we are preparing this implant abutment unit, you know, under the hood here, hammering the abutment into the implant according to the manufacturer guideline. And then this went directly in the broth here. And you can see the broth is very cloudy because of the bacteria. For the microbiologists in the room here, we use an optical density of one. After twenty four hours of incubation in an anaerobic chamber at 37°C, the implant abutment units were briefly washed in PBS, fixed in four percent formaldehyde, and carbon coated, carbon coated to be looked under scanning electron microscopy. At this point, they were sent to the Forsyth Research Institute to the laboratory of Dr. Ziedonis Skobe, who did a magnificent work looking at these samples, and you’re going to see the pictures in a minute. And this is what you see. This is the implant abutment unit that you see under the electron microscope. Here you have the body of the implant, and here you have the abutment, the coronal portion, and this is the post that goes into the implant. And this is the portion that is of interest to us. When Dr. Ziedonis Skobe saw this, he called me up and said, oh my god, we have a problem. I said, what do you mean? He said, Well, I can see a slight gap between the abutment and the implant. Okay. We took apart the abutment from the implant. And now you’ve seen Dr. Skobe, he’s a very muscular guy, you know, he can lift hundred pounds with his hand, no problem. And he had difficulties in unlocking the abutment from the implant. And you can see here marks that are left from this, you know, the plier that we use to try to unlock this. Anyway, once unlocked, this is the implant, outside portion, and this is the implant well, and this is the abutment. And look at where you find the bacteria. You find the bacteria on the outside here, and they progress all the way here, and this is a line beyond which there is no more bacteria. It all stops here. Okay? And this line, this white line, corresponds to the apical portion of the chamfer. I call this the coronal chamfer of the implant. Okay? So the white line corresponds to this line here, meaning that there is nothing in here, there is no bacteria in here at all. Everything is above or around. This black mark that you see here corresponds to this portion of the internal well here. And this is where the real seal of the implant abutment connection takes place. That’s where you have the metal to metal cold welding that creates this impenetrable seal. At this point, you know, you can ask, so what is happening here between the bottom portion of the coronal chamfer and the start of the “real seal”? Well, this is a bacteria free zone. What Dr. Skobe had shown the first time when he was looking at the implant, the very small gap, if you wish, is something that is less than zero point five micron. Okay, you can see here this is the abutment and the implant. If you were to put your eye right here where the black arrow is, this is what you would see. This is the area where you have this very small crack, and again, it’s less than zero point five microns. Now if you remember, the smallest microorganism that we know of, one of the smallest, AA, or Acnovaceus actinomycin comitans, has a diameter of zero point five. So if this space is less than zero point five, there is no way in the world these bacteria are going to get into that space. This is a different view and different magnification. Here you have the implant, the coronal chamfer and the implant well. Nothing on the sides of the implant well, absolutely no bacteria, whereas on top here where the chamfer is, plenty of stuff. Okay? But it stops right here. And this, ladies and gentlemen, is the implant well. And what do you see? You see nothing, because there is nothing to see, there is absolutely no bacteria in here, it’s very clean and sterile. So the results were that none of the ten tested samples showed microbial presence past the implant abutment junction. The inside well of all implants tested, as well as the bottom of the abutment taper, were free from microorganisms. Now the second phase of the experiment was to see if the bacteria could seep out from that implant. So we used fifteen implants to that effect. Nine were assembled, containing zero point one microliters of a bacterial gel, using the same bacteria that we used for the first experiment. We just this time entrapped them in the gel and put them into the implant. And this was a test group. We had done three unassembled implant abutment units with zero point one microlitre of bacterial gel, we call this the positive control. Now why is that important? That’s very important because you want the bacteria to be alive. That’s a marker that tells you that the bacteria during the experiment were alive, so that at the end, if on the test group you don’t see any bacteria, it’s because the seed was effective, not because the bacteria have died during the experiment. We used also three assembled implant abutment units with no bacterial gel, and that was the negative control. The reason for that is that you don’t want to have cross contamination, or some bacteria from the outside area contaminate your samples. This tells you if the negative control stays negative at the end of the experiment, that there was no contamination, and it was all done in a sterile fashion. So all these implant abutment units were incubated in a sterile broth for three days in anaerobic chamber at 37°C. This is how we did that. This is a micropipette containing the bacterial gel mix. Zero point one microliter was delivered at the tip here of the abutment, and you can see it here. Then the abutment is put onto the implant, hammered in place, as we should do it in the mouth, and then put into this sterile broth. The whole idea was to test and to see if the bacteria could come out from here into the sterile broth. Okay, here on the top of the slide you have the two test areas, those are the implant abutment units with the bacterial gel in them, both of them. And this is the positive control unassembled abutment implant with the bacterial gel in there. Three days later, what do you see? The positive control is all cloudy, and that’s great news for us because it means that the bacteria were alive and kicking. Nothing died, the bacteria were fine. And what you see in the test group, clear broth, which is telling me that nothing leaked out from the implant. This is the negative control. The negative control has stayed clear during all the experiment, telling us that there was no cross contamination. Now, of course, at this point, you can tell me it’s not because you don’t see anything or you have a clear broth that there are no bacteria in there. And of course, you’ll be right by saying that. So what we did was we take some samples from those tubes, acid tubes, and plate them to culture them, to see if anything would grow from those agar plates. So we pipetted twenty microliters from all the glass tubes and plated them individually on agar plates for cultural purposes. Those plates were incubated in an anaerobic chamber for a week at thirty seven degrees Celsius to allow for the bacteria, if they were there, to grow. At the end of the week, the plates were taken out from the Arabic chamber and analysed. And this is what you could see. On the left hand side here, you have the test samples, and as you can see, nothing grew on the arrow plate, which tells us that the broth was indeed sterile, there was absolutely no bacteria in there, since there is nothing growing here on the plate. Whereas the positive control plate, you can see plenty of bacterial colonies. So in conclusion of those two experiments, we can say that all of the nine test samples, the implant abutment unit containing the bacterial gel, showed a clear sterile broth at the end of the three days of incubation. The three positive controls, which are the unassembled implant abutment units with the bacterial gel, showed cloudy broth confirming the viability of the microorganism throughout the experiment. And finally, that the three negative controls, which were the noninfected implant abutment units, had clear broth, showing no cross contamination. Now, for those of you who are still skeptic after these experiments, no. This last slide or this last experiment should alleviate all your doubts. The Bicon people, being very, very thorough, wanted to have a cross section of their implant abutment unit. So they provided us with this implant abutment unit that we sent to Dr. Thomas Diekwisch, the University of Illinois at Chicago. What he did was to, using a light curing resin, embed this sample in that resin, then use a precision saw to cut in the middle of the implant, and that’s not something easy, it’s something very, very difficult to do properly. He grounded the specimen to a thickness of twenty to thirty micron, which is even more difficult to do. And finally, he sent it to Dr. Ziedonis Skobei look at it, so that it could be looked at under scanning electron microscopy. And this is what you see. This is the implant cross sectioned. This is the abutment with the coronal portion here, and then the post. Of particular interest to me is this area here. Okay? But you can see how tight the junction is between the two metal. It’s the metal metal cold welding, etcetera, that provides this hermetic seal, really. And this portion here, you see it up here, there is very little or none space at all, really. It’s impossible for any bacteria or anything that’s in the mouth to go from here, the outside, to inside, here down to the apex. This is really impossible, unless we believe in miracles, but it really is impossible. Now, like every successful product, think Cartier watches, Rolex watches, for the ladies, Louis Vuitton bags, Bicon has been copied, apparently. A couple of months ago, Marincola and Tom Peterson came to see me with something that looked like a Bicon, smelled like a Bicon, but was not a Bicon. And this is this product here. And what they did is they asked me, can you run all the experiments that you did, you know, testing our products on this particular Microtech product? And I said, sure, it’s going to cost you the money, but we’ll do it. They were happy to oblige, and we did it. So we did it outside in and inside out, exactly the same way as we would have done with their own implant. And these are the results of the outside in. Again, this was done by Dr. Zizkobi, a very beautiful work. And when we looked at these samples, again, I repeat the outside in, you put the abutment on the implant, the implant in the bacterial broth, and then you disassemble to see where you find the bacteria. Well, first of all, we found a lot of manufactural defects: cracks, fissures, concavities, convexities in places where they shouldn’t be. Also, presence of bacteria into the implant well. So after seeing that, the second phase was the most surprising to us. This is a test sample. And what do you think this is? Excellent, excellent. Mark Wang, excellent. Mark worked with us at Harvard, so that’s why he’s but that’s it, yeah. This is bacteria. And this here is a sterile broth. I put it side by side so you can compare. This is how it should have looked like if you had an impenetrable seal, which you don’t, because bacteria can seep out and colonize the broth. Okay? Okay, now this should be enough for no. But since we’re a very thorough scientist, we try to or at least we try to we took some sample from here, again twenty microliters, and plated it on the agar plate. And we recuperated the same bacteria that we put in here, we found here. Okay? So this tells me that this implant here is not really how can I say that does not have a hermetic seal, okay? So beware of copies. In conclusion, is your current implant a septic reservoir? This one is not. I can assure you, after having worked with this for a few months and attacking it from different perspectives, microbiology, mechanical, etcetera, etcetera, this one is very well sealed. Now, all this has been accepted for publication in Germany, and it’s going to come out in a month or two. So you’ll have the whole full report if you’re interested. I just got the galley proof that was on vacation last month. I also had to email and do all the work from France, but it was accepted, and it’s going to come out in print next month, I believe, in Germany. This really ends my presentation. I would like to thank a few people, Dr. Ziedonis Skobe, who did a fantastic job again with EM Martha Warbington, who is my technician, does most of the work Ming Fan Su, who is faculty at the school, they also participate in all these experiments Thomas Diekwisch, University of Illinois, who did this cross sectional study, which is a very, very nice one. And finally, last but not least, Tom Peterson, without whom any of this would not have been possible. And this ends my presentation. Thank you for your patience.