What Causes Dental Failures?

Where do failures happen in dentistry? At the micron level. Bacteria create infections; micromovements initiate cracks; these are the root of failed restorations, infected pulps, and cracked teeth. Experiencing his own failures from traditional and early adhesive restorations, Dr. David Alleman discusses how thinking small led to significant advancements in restorative outcomes.

Articles referenced in this episode:

• Intro-3 Magne  P,  Belser  U. Rationalization of Shape and Related Stress Distribution in Posterior Teeth A finite Element Study Using Nonlinear contact Analysis. J Periodontics Restorative Dent. 2002;22-425-433
• Magne P, Oganesyan T. CT scan based finite-element analysis of premolar cuspal deflection following operative procedures. J Periodontics Restorative Dent. Volume 29, Number 4, 2009:360-369.

2025 training programs:
Biomimetic Mastership - class starts May 12. Learn more and register at allemancenter.com/mastership

In-Person SLA Workshop Dates:

• August 8-9
• October 24-25
• December 12-13

Learn more and register at allemancenter.com/training

Instagram
@david.alleman.dds
@davey_alleman_dmd
@allemancenter.com

YouTube
@allemancenter

Transcript

0:33

Well, welcome to season two of the six Lessons Approach podcast. I'm Doctor David Alleman. I'm excited to be back for another season. Before we get started, I have season one giveaway winners to announce. We had so many participants that we selected two winners. Congratulations to Bryam and Mark. We will be contacting you on Instagram to get your SLR swag. Now for episode one of the new season. We want to introduce the concept of why restorations fail. The restoration failure is what drove me to quit dentistry. I was a dentist for 17 years. I did traditional dentistry to the best of my ability, with fillings and crowns and root canals, and I had failures. I had failures, sometimes very quickly in the first three years. Then I would have some failures that would be a little longer, seven years perhaps, and then ten years. But after 17 years, I had seen enough of my own failures to wonder, is there a way to prevent the failures? I know that I did my best, but could I have done it differently? And so those questions were never answered until I was connected with Adhesive Dentistry in 1995, and the adhesive dentistry that I was connected with came from Japan, and it talked about sealing the tooth. And the idea of sealing the tooth made sense to me because even before I went to dental school, I was very well aware that decay was from bacteria. Bacteria could be sealed out of a tooth if you had a seal that was small enough. Bacteria on the micron level. If you look at your fingernail, that's an average fingernail thickness is 500 microns, and so you could be able to fit 500 bacteria across your fingernail. That's how small they are. But that's the cellular level bacteria or a cell. And those cells have shapes and sizes, and they have structures inside of the cell, just like every cell in our body has cellular elements. And so as a microbiologist, my major, I understood that level of size. And then as a chemistry minor, I understand that below the cellular level you have molecules. Every cell works on a molecular system that produces energy and produces and reproduces the cell. And all of these chemical reactions that are on the molecular level, they have a new level of smallness, not the micron level, but the nanometer level. So a nanometer is 1000 times smaller than a micron. And then molecules are made up of atoms, and the atoms are on a scale that is called angstrom. An angstrom is one tenth of a nanometer. So ten thousandths of a micron. But in the world of dental failure, it's always on the micron level. Micro leakage allows bacteria to get in and the best crowns, or the best fillings that I could ever do, had been shown in the research that I was discovering to be at about 25 microns. And so the best crown that I could ever do would still have the ability to have 25 microns living underneath it. But most crowns with most techniques would be around 100 to 200 microns under function. Well, if the bacteria what causes really k, then if you're able to seal out the bacteria so they can't touch the dentin, then that has a possibility of stopping the decay process. And so as I was being introduced to adhesive dentistry and the idea of sealing a tooth, which we call a bond, the idea is that if you could stay bonded, then you could stay uninfected. Wow. That was a real game changer in my mind. And when I was introduced to that concept by Ray Bertolotti, because he had a PhD in chemistry and I only had a minor in chemistry, I respect that. At least he knew what an atom was, and then he knew what a molecule was. But sometimes chemists don't know that a biological entity like a cell is different than an airplane wing or, you know, a car fender or some material made out of molecules and is used for different applications. But Ray Bertolotti, you know, he's a smart guy, and his expertise in ceramics led him into the research field of ceramic, metal crowns, PFM crowns. He was an expert in the world on how to make ceramic bond to the metal cause underneath the ceramic crown. That was his expertise. But because he was in the world of research, he came across a group of researchers in the mid 60s out of Japan that were talking about these ideas of bonding, in which we've talked about an early session emerged in dentistry based on epoxy chemistry from the late 30s into the early 50s. 1951 was the first bonding system. The first molecule of polymerized and bonded to that tooth was called Severton And certain one had a molecule called GPDM. But then in the 70s and 80s new chemistries were introduced and the ones that came from Japan had proprietary molecules, had proprietary solutions, had proprietary concepts of how to establish the bond. The body systems for America. We just made them simpler and we had good marketing. And so we sold them to dentists and I bought them. They didn't work. They didn't bond to dentin. They didn't stop recurrent sensitivity or decay. It was pretty, pretty much not truth in advertising. You know, if somebody tells you something in advertising, the basic rule of economics is beware. If you're the buyer, the seller is just trying to get you to buy their material. So I suffered through that in the 80s and knew that adhesive bonding was not really great. Interestingly enough, I had a connection with English dentistry established when I was a junior in high school because I was an exchange student and lived with the dentist in England, and because I was a dental became a dentist. We stayed in contact from 1968 to 1982, and the dentist who I lived with sent me some material that had the I had the label. This is what it was called Miracle Mix. So Doctor Parsons sent me some miracle mix. And this was supposed to be an adhesive material that you could use for crown buildups, and it was glass ionomer. I barely knew what a glass ionomer was or could be, but this glass ionomer was made a little stronger with a mixture with amalgam particles. So it was black. Doesn't matter under a crown. But still, you know, I read the instructions, I use it for a build up, and then a year later the build up fails. You know? So my exchange student dentist mentor, in some ways, he was a great oral surgeon. He loved to extract teeth and make dentures for young people in England that would get free dentures. They did it when they were 18 or younger. I mean, this is crazy, but this is my introduction to real dentistry in a different country. But this miracle mixed glass ionomer or the GC was the company. Originally it was SB and then the GC, but the material in Japan and I actually made it somewhat better. It had some bond to then, but not enough to sustain the forces of chewing. Okay, so more failures in the 80s as I'm a young dentist, young family growing up trying to make my living doing fillings and crowns and root canals. And as I saw these failures, the idea in 1995, when I introduced the idea of sealing at the less than micron level, was very, it's a paradigm shift. And that began in an improvement in my dentistry, was when I was introduced to adhesive dentistry, because one of the failures of re-infection based on this micro leakage was very much based in the science. And the more I studied, the more I understood. And that went pretty well. For about five years I made the progress on adhesive science to know what the issues were in establishing a hybrid layer, what the issues were in producing materials that could produce these hybrid layers that could make a strong connection in the submicron world. But then after five years of success and progress, adhesive dentistry, then I encountered and came face to face with something that I knew was causing failure in my dentistry. And that failure was fracture and so the fractures first had to be visualized. Now, the visualization of the infections, these micro leakages from bacteria was helped tremendously. When I was able to carry out detecting dye in 1997, it took me two years from the time that I heard about caries stepping down between the time that I actually had in my hands that I could use it. And so for three years, I was very excited and learned some things and developed some ideas. And I every year I would be mentored twice a year by Ray Bertolotti Yosemite or Lake Tahoe. Sometimes you would come to Utah. So I probably attended 20 to 25 lectures in those, five years. But I understood the cracks were not being addressed because at the end of every lecture, an adhesive dentistry, nobody talked about cracks. I could see the results of cracks, but I couldn't see a crack until I was inspired by my mentor in endodontics.. Steve Buchanan Steve Buchanan was my class valedictorian and at UoP. I was glad to graduate in the middle of the class, get on with my life. He was number one in the class. I had known him from the day before dental school started. We were in the same line to get our pictures taken for the yearbook, and so that's when I met Steve Buchanan. He later became the real innovator and real paradigm shifter in endodontics when he embraced rotary instruments, nickel titanium technology, and the concept which was key of chemical removal more than mechanical removal of pulp tissue, the dissolving of pulp tissue with his technique took time. It made endo slower, but it made it better. He also developed the concept of a patency file, which he taught me, and when I took courses from Steve, I was introduced to the microscope. And so at the end of 1999, I saw endo through a microscope. But of course I took with Steve at the university, the Ohio State University in Columbus, Ohio. For two days. I was with the endodontists who were using microscopes, and we were introduced and I bought a microscope. And so from the beginning of the year 2000, I could see things twice as good, three times as good than the loops. I was using before. And then the investigation visualization of cracks became the burning question, because I knew that cracks had a beginning and had an end, but a catastrophic failure you had. You couldn't intervene if you had a mid root fracture, the tooth was lost. But now with a microscope I could see smaller cracks. I could see the cracks had a direction where they vertical, where the horizontal where they oblique. And so as I started to investigate the crack principles, the only literature that was available was engineering literature. And so I had a close friend, Dennis Groh, who is an engineer, bachelor's degree engineer. But he had on the job training in fracture mechanics, back propagation, crack stopping because he was working his whole career on carbon fiber airplane wings, nose cones at Hill Air Force Base for the United States government. So he had advanced practical experience with cracks developing on these multi-million dollar aircraft. And as I talked with my friend Dennis about this and other engineers, they would always say the same thing if you have a crack, you need to treat the crack. You can't just bond over it. You will need to actually dissect it or somehow interrupt the crack at the tip. I mean, that was the terminology they use. And of course they use magnification, and they used adhesive and fiber technologies to bond these dissections after they had removed the crack. But first they had to remove the crack before they bonded over it for the repair. And then other technologies that were composite technologies, like metal technologies, they had the same philosophy. And they found out that if they did dissect the crack and they did weld the crack, now they had actually a repair, they could be twice as strong. Is the pipe the hip fracture started to fracture. I mean, all of these things, when you're not an engineer, it's new terminology. But I would buy textbooks that were less mathematical, less technical, written for people who weren't engineers but worked with materials that were prone to crack. And these books would still reinforce the idea that all of these cracks start on the submicron level. So the movements that actually broke materials made of molecules, the movements were on the nanometer level. Well, this seal that we're trying to seal, the bacteria is at that level. Also, submicron nanometer seal will keep micron sized bacteria out about the micro movements. The micro movements are on the same scale. Micron movements were earthshaking to molecules because a micron is 500 times bigger than a molecule. And so if you have something shaking, small things that is large. These micro movements that we have in teeth regularly are like earthquakes to the atoms. But after an earthquake you can still settle down. And so you'd have this shaking and then it would settle down. You have the shaking, it would settle down every time a tooth is bitten on. We have about three microns of movement spread throughout the tooth. Now the tooth is nine millimeters wide. So three micron is shaking. It's not a lot, but on the atomic level it is. But the tooth as the ability to withstand these movements and then come back to normal. So it would expand, come back normal expand, come back to normal. But if the movements were too big, then a crack would initiate. So once the movements got to be micron level and you had a gap into the tooth, which traditional restorations of fillings inside a tooth or crowns outside the tooth, there is always a gap of 25 to 200 microns, whether it's a crown or a filling. Those were the measurements that were being produced, and some of the most specific measurements were coming out of Pascal Magne’s lab and his connection with the president is Urs Belser. They were very exciting to read. I remember the article I read in 2007, Urs Belser, A Finite Elemental Analysis. using engineering technology to show where stress concentrations were five years later, these stress concentrations were actually given a size by a work done by Tevan Oganesyan and working in Pascal Magne’s lab and published. And all of a sudden we see that this expansion of a normal tooth of around three microns distributed over the whole tooth. If you had a filling in it, that expansion of three microns went to 175 microns opening. So that would be 100 microns on each side of a silver filling, or 200 microns underneath the crown, as the crown is not compressed, which is ideal, but usually a crown is torqued And so that talking where there is not a support of the tooth to the crown leaves a gap, and that gap allows bacteria to come in, but also allows cracks to begin because of the movements causing the stress to the molecular level, which can cause the molecules to separate. And that's called crack initiation. And then that crack initiation when it's there, then it becomes aggravated at a faster rate, the larger the crack gets, until finally something falls off or crown falls off, which for the first 17 years of my career, I saw crowns in the hands of the patients. Now, for the first ten years, those crowns that were done, that were in the hand of the patient that wanted it fixed were done by another dentist. So it's like, well, that's obvious. That Crown wasn't done the right way because my crowns don't fall off. I mean, I'm so, you know, like, I don't want to be proven that I'm not a good dentist. So my rationalization is always, well, this failure was somebody else's failure. And then on ten years and one day my crowns started falling off cracking and the tooth was inside the crown. And I'm going, that crown was at a good marginal seal. I submitted it properly. I had the build up properly done and now this crown. There's nothing on top. Maybe I can reattach it to the root, but then sometimes the fractures would go not take the crown off horizontally, but they would go vertically into the root. And then at that point the crown couldn't be even redone at any in any, way. The tooth was lost. And so about this time, 1995, when I'm introduced to a way to improve dentistry through solving the problem of reinfection after five years. Now, the second major problem in my clinical practice was fractures that caused at least the the need for a retreatment. But and several times, many times it was a catastrophic failure. And then beginning that that intense literature review on micro movements and engineering concepts from 2000 to 2003 under microscope. Then I developed really the missing link, which is lesson two. And so both lesson one and listen to our failures on the micron level. But if you can have a seal or a tooth that's connected on a nanometer level, by eliminating the decay in the peripheral areas and eliminating cracks in the peripheral areas, that's like a tooth. A tooth is connected side to side, front to back and top to bottom on the nanometer level. And that's been the goal of biomimetic restorative dentistry in the six lessons approach since I started teaching it over 20 years ago. But again, you know, most dentists aren't really that interested in chemistry. They're not interested. They're interested early in dental anatomy, which to me is like, are you kidding? You're a dentist. You should know some very important details about teeth. And if you have to learn some protein chemistry to understand collagen, that that's what you should do. If you have to understand some inorganic crystallography to understand hydroxyapatite crystals and how they interact with these collagen molecules so that they're tough, well, I think that's what we should do. That should be the basics in dental school, but unfortunately it is not. We do not have a sophisticated dental curriculum in chemistry. We do not have a sophisticated dental school curriculum in dental anatomy. But that could change. And we think it's changing because dentists who understand the difference in what it's take to prevent failures, you have to prevent micro leakage and micro movements. So by preventing micro leakage, less than one micro movements less than two, you're on a strong foundation to have a sound foundation that mimics a natural tooth. And on that sound, biomimetic foundation, we can recreate a biomimetic restoration of the missing two structured chips and loss from fracture or decay. So that's season two, episode one. Until next time. Get bonded. Stay bonded.