Enamel Replacement: Ceramic vs Composite

What is the best material for enamel replacement? It depends! When selecting the material of an onlay or overlay, understanding how a natural tooth functions during occlusion is essential if your goal is biomimetic dentistry. Harder is not better, but rather mimicking a natural tooth’s bond to itself and its modulus of elasticity will aid in selecting your enamel replacement material.

In this episode, Dr. David Alleman reviews ceramic, composite and gold and outlines best practices for completing the final steps of a biomimetic restoration.

Articles referenced in this episode:

• Wendt, S. L. (1988). A laboratory and clinical evaluation of a heat-cured composite resin inlay. [Master’s Thesis, University of Alabama].

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

Welcome to season two episode eight of the Six Lessons podcast. We are happy to, continue this discussion of some of the history and some of the important, efforts by certain pioneers in adhesive dentistry. And today, we'd like to talk about a, a pioneer that, has been totally forgotten. But, had the opportunity years ago to meet, the author of this master's thesis. His name is Stan Wendt And Stan Wendt when he, was looking at different options to restore the occlusal surface of, conservative restorations. Was the one who did the best investigations of composite. Most dentists have a bias against composite on the surface, thinking that ceramic are superior. Well, you have to say, in which way do you think there's superior? And you have to talk about the individual characteristics of a ceramic on clay versus a composite on clay. And even more important, a composite overlay versus a ceramic overlay. Some of this information that, I'll be talking about has not been published, but has been discussed. And there is some research and I have my practice based research network in my own cases to validate this. And so it could be repeated, but, I don't see many people following up on the research of Stan Wendt. But what Stan wanted to know is that if you took composite and you, like, cured it, it was known that only 60, maybe 65% of the monomers would be polymerized. And if you have, more polymerization of the monomers, you get a change in the modulus of elasticity. And theoretically it should be a change in the wear of the material. But it wasn't that easy. There was a material, that was brought onto the market, in the 80s that had, composite that was highly polymerized through a pressure and a intense light, but mostly pressure and heat pushed that 60% polymerization into 80% or even 90%. And, the material was called Targus. Targus Vectrus another material called concept, came to the market. But these materials that were over polymerize had a problem. There was no way to bond the material that didn't have free monomers available in it to polymerize in the next polymerization reaction that would connect the enamel replacement to the dentin replacement. And so this idea of over polymerization or over curing, there's a material called from three M that is called Lava Ultimate that had the same problem. And once you do that then your bonds are decrease. Now in ceramic the bond is not a free radical polymerization connecting the polymerized monomers of the entire surface with the monomers that are on the tooth surface. And so ceramic has the connection not through the polymerization, of the monomers to the entire surface, but through a silanization, process where the silicone connects to the ceramic in an ionic bond. And that ceramic, bond can be very strong, but it's not as strong as a cohesive composite bond where you have covalent bonding of composite molecules to composite polymers. Well, these kind of questions. Most dentists don't even want to think about what's going on. But if you want to have long term success, then you need to understand these things. But what? Stan Wendt, wanted to find out. And he did find out is in the contact area. If you had a composite only to a composite only, contact, then what would that do? Long term. And so he was evaluating the wear of these composites, whether they were directly composite, polymerized with the light, or if they were subjected to heat and added pressure to get a higher, polymerization and they found out that the wear improved a little bit. But again, the downside was the lack of the ability to add composite to a composite surface that was over polymerized. another important finding was that if you had a composite rubbing against the composite, which is called a two body, where then that would wear more than if you had ceramic to ceramic. So a ceramic touching a contact of ceramic has wear resistance that composite does not have. But the ceramic not wearing the ceramic. If the ceramic is get against the natural tooth, it can have a wear against a natural tooth, but not much if it's enamel. If you had deadened exposure, it would wear more. And these investigations led to, the concepts that, Stan, when I talked to him at his home, years ago, we talked about some concepts that, Gary Unterbrink could introduce into my knowledge my my mentor, Gary Unterbrink, talked about a two body wear and a three body wear. And what he said and what I've seen in my own cases is that if you have a natural tooth on top and a composite overlay on the bottom, then the composite overlay continually is in close contact with the tooth and that the tooth will wear that composite. And that's called a two body contact configuration. Well if you have ceramic on the bottom then that two body wear actually wears the natural tooth. But how much. ceramic. That's polished or ceramic that is glazed has much less aggressive nurse against the natural tooth, very rarely. Is that a problem on posterior teeth if we have high polish and glazing, but on interior teeth, well, you would see, you know, over my career is that if you had the lingual of a crown in ceramic, and it was not polished and not glazed, then the lower incisors would wear and it would be very noticeable both esthetically and eventually functionally, those lower incisors could be shortened, significantly. And so the solution to that problem anteriorly was to make a lingual metal in the crowns. When veneers came, we were able to completely conserve the lingual of a natural to structure. And Pascal Magne in his book, made a very significant contribution into prep design of partial ceramic or partial coverage of anterior restoration, showing that if you do infringe or encroach on the singular on the lingual of upper incisors, you change the biomechanics of an incisor tooth, and it's a negative, situation that increases the flexibility of the tooth. Where have you preserve the single? You have a much stiffer substrate and you have a better functioning restoration. And, of course, if you have the singular in the lingual of the tooth in enamel, then it doesn't wear lower incisors in the posterior. How does that work out? Well, it works out also that if you don't polish ceramic and it's against the natural tooth, it will wear it probably around 30 microns per year. If you have composite this in a two body where continually, the natural tooth will wear the composite about 50 microns. Now 50 microns over ten years is, half a millimeter the thickness of your fingernail. Now, in ten years, if you lose a height of your fingernail, you know, in 50 years, you've got a little bit of a wear. But the tooth in the natural, condition has the ability to have the supporting bone and soft tissue erupt, keep the tooth into occlusion, and you don't have a period on condition that, you know, in a normal tooth. And so that type of wear on a tooth, the adjustments of the mask artery system are, well known. And, for most people, it does not become a problem. But in this composite versus composite, if you're losing 50 microns against 50 microns with an overlay against an overlay, then all of a sudden you have what's called a closing of the vertical dimension. Closing the vertical dimension does change the relationship of the head of the condyle to the disc and disc apparatus and the glenoid fossa, and theoretically it can cause a compression that can cause adhesions. It could lead to a clicking and popping and a TMD condition. But these would take decades to happen. Usually that will happen. In a situation where there is hyper function from hyper musculature and, and sometimes a lot of stress, can increase the amount of pressure that we're putting on our masters and our temporal muscles. So the whole idea of TMD as it relates to restorative dentistry, to not lose vertical dimension is an important goal. But again, clinically, it's very rare that that comes up. But in biomimetic dentistry, when I started to do composites exclusively for the first ten years of my approach with the six lessons approach, I would find that if I did overlays, then I would have a flattening of the secondary anatomy and then that secondary anatomy, you know, it's not as functional. But again, the type of diets we have don't really require sophisticated cuts for us, relationships, flat teeth against flat teeth still are able to mesh, but usually in a dentition that has not been mutilated. We have 1 or 2 teeth that would have an overlay, and then the rest of the teeth would have cusp fosse relationship. And so the ability of the brain to capture that envelope of function, has not been shown to be impeded. But what Gary Unterbrink told me and Pascal Magne actually had some clinical research. That he has not published that validated the things that I've seen over the last 20 years is that if you say one cusp. And make an online versus an overlay where all the cusps, are reduced and then restored, then that one tooth or that one cusp of natural dentition keeps the relationship of the opposing tooth into a two body situation that's similar to tooth to tooth. And so the wear would be around ten microns. In a year. Very small. the only with one cost per two cause per three cuts preserved, then the only the it would wear, it would wear in the first four years in this two body configuration where it would lose 50 microns. But then at year four and five that wear would stop. If you're preserving one, 2 or 3 cusps in a only preparation versus an overlay preparation, where all the cuts were reduced and the composite, it would be, restoring all four cusps. And so if you did have a situation when restoring vertical dimension on many teeth, was very important in the treatment of a severe TMD patient, then the maintaining, the vertical dimension was ceramic. Obviously is is an option. Cusp fosse relationship for the efficiency of mastication obviously would be improved. And many presidents that's their go to idea in occlusal function. But in the occlusal schemes that I believe have been validated around the world, we don't need that many cusp fosse relationships to program our brain into efficient movement, subconscious movement that's controlled by the cerebellum, not the cortex, but these chewing moment motions that are in our cerebellum program by the cranial nerves that control our jaw movements. They can be programed with a simple three point contacts, one on each side and one in the front. Once that's contacting, then the brain says, oh, I have a place that I can reproduce and the brain is able to get into that position. Very predictably, we don't need 28 teeth contacting and cosponsor relationships in, the working non-working protrusion of, you know, all these things that, process it on us love to talk about and teach in dental school and confuse all the dental students, especially the difference between a denture and a natural dentition. I mean, this is information that, newly graduated dentists would never want to have a test on. But in reality, by understanding how different jaw movements relate to different wear, patterns on teeth and different materials can influence those wear patterns and the jaw movements. It leads to some very sophisticated occlusal concepts that we touch on and teach in the six lessons, but they've actually been validated by a president named Francesca Vailati, who now teaches in Europe. And it just shows that you can get guidance into this maximum intercuspation through cuspids which is the traditional precedent, training, but also through posterior teeth. And I know that John Kois also talked about posterior guidance. And these ideas all, require a certain knowledge of how a brain works and how a cortex works in programing initial movements, but how those movements can become smoother as they become practiced and put into the cerebellum but the brain is very smart. It's very able to change movements and the where the comes from chewing million times a year. You know, we have some control. But my solution has always been use composite orderlies because they're highly bondable More bondable than ceramic. And if you're able to preserve one cusp then you don't have a problem with losing your primary anatomy. And the body of where stops at about four years, because now you have what's called three body wear, which is the opposing tooth, the restoration. But as the restoration has, lost a little, little of its surface depth, then now you have a bolus of food that comes between the tooth and the restoration, and that's the third body that is in this controlling of the wear. So now you just have a layer of food the tooth don't need to touch to chew and digest food. And so the two body wear is limited and becomes a three body wear. And you can have composite on orderlies. The last for decades or into our third decade with many of these, restorations. But Stan Wendt as I talk to him about these concepts that I had learned from my mentor, Gary Unterbrink he understood those, and he felt like his research, validated those that even if you had a highly, polymerized restoration, it would not be anywhere like ceramic as far as, contacting a natural tooth and having less wear or a little bit of wear on a natural tooth. So these composites always were the ones that wore. But particularly if you have a composite versus composite, that two body wear composite, you never have a third body in a contact area unless you have a lot of wear, a fracture, then you get food impaction. But that's not a mascot or a function, it's just there. So what was the solution? Well, the solution, if you wanted a person to have tight contacts for ever, would be ceramic on clay versus ceramic only in the contact area. But as I have my own teeth with composite orderlies and I have my own teeth that actually have some diasporas where there's naturally occurring spaces and I get food in those spaces, often it doesn't bother me that much, but I'm not that sensitive as my wife, if you have a space between the tooth, you get food. It's a motivation to floss, obviously. But patients, when they come in and say, okay, you know, I've had this restorations been there for ten years, I'm getting, a little bit of food impaction, you know, and I floss it and it's not, a very tight contact. The repair on a composite to composite, is so simple. It's just a bulk fill of a three by 3 or 4 by four preparation in approximately. Because you're not having to bond to dentin you're just bonding composite to composite and that composite to composite. There's no hierarchy about ability. So any shrinkage will go to all the walls equally. That composite will change its molecular network a little bit. Basically you just bulk fill it, put the lid on it. Just put a thin matrix band or sometimes I just put a, a piece of, Teflon tape that's about as thin as you get. And then you bulk fill it, and that tight contact is like glue. Now, the patient can't floss. Well, you know, it's. You've all dentists have had these, situations where context is too loose, too tight. Some patients, like, you know, the soft bed, some like the hard bed. And Goldilocks is where the contact is the right for most people. But all of these, ideas, when we choose the enamel replacement, become very important as long as we understand what the downside of any particular, material is and what the benefit is in my view, the composite on is always has more benefits and downside. If this to body wear is a downside, you can monitor that and you can repair it very easily. But you never have a D bond. And so I've never had a debate of composite, but I've had doctors that I've trained who are enamored with ceramic. For the occlusal enamel replacement. And if they get too thin, particularly after a occlusal adjustment, if they're less than a millimeter and a half, they get to a millimeter, then those tend is fracture. At four years, it can be repaired. Obviously. And I've done that mistake and I've repaired them with composite. And then the composites don't have, that problem. But if you have a situation where you'd like, very nice contact to contact, that is as much as, the two body where is as biomimetic as enamel, then the material actually would be gold. If you have a gold on layer inlay and the contact is with the gold on layer inlay, the two body wear is about ten microns on each side, every year. And then you have a little bit of visual shift with the natural dentition. Is is part of the the normal progression of teeth as they get older. and those long term, gold, gold contacts are about as good as you can get. But gold is a little more expensive. It's, a little less esthetic on the back teeth. Sometimes patients like that, sometimes patients don't like that. But, these conversations that I had with Stan Wendt. And then he, gave me a copy of his master's thesis that was published in 1988. 1988 is getting old. we're about 36 years, since he had his master's degree, I haven't talked to stand for a decade. His master's was done at the University of Alabama. But, the heat cured composite resin inlay has the, advantage of having a higher polymerization, but that higher polymerization doesn't really, cause any, any problem. But in our technique, we have used a heat modification of the onlay to make the polymerization of the onlay as close to non shrinking as possible. That usually is a situation where you have an advantage if it's a large inlay. But we do put, on laser inlays into a toaster oven. Toaster oven is a very inexpensive, piece of dental equipment and cost you $30, $40, but you need to have a candy thermometer to control your, your temperature and the ideal temperature is 125°C. That's the same as 250°F. And so 250°F. If you put your, only into that, that takes that polymerization, to the, the maximum that it will under light curing, which is only that 60%. So you still have, 40% of your, monomers in islands around the polymers that can be totally polymerized. that situation can be achieved in seven minutes, whereas your bio base will take about 30 minutes to get to that 90% of its polymerization. And when you say 90% of his polymerization, again, that means 90% of 60, 65% conversion. It's not 90% conversion, but 90% of the 60 to 65% conversion of your bio base will take a 30 minute period. Well, the on online can get there in seven minutes if you add heat. So now you have a 95%, converted bio base that has 35%, maybe 40% of the monomers after air abrasion those 35 or 40% of the monomers are available to get a diffusion of radicals from the cement layer that gets activated with light. And so your bio base has uncured adhesive, and it's into that increased surface area from your air abrasion that we talked about last episode. And so now you have this layer of monomers that is connecting or touching the monomers that have been exposed with air abrasion. And then you have the heated composite layer. And then you have the intaglio surface that again has had increased surface area to expose the 35 to 40% of uncured or rise monomers in the intact wheels surface of your heat cured only. And when you squish that all together, you have the only. You have your adhesive, you have the heated composite, you have your adhesive, and then you have your, air abraded. Only squish those all together, and the light cures all of those levels together. So you have a diffusion of these free radical monomers in the heated composite going to the top towards the only that's called diffusion towards the on. And then you have a diffusion towards the bio base. And the light is activating the camphor quinones that are in the mainly your heated composite. And those camphor quinones start the free radicals to go diffusing towards the entire surface of your adhesive that's connecting to the air abraded surface of your onlay And then down you have the free radicals as they grow into oligomers or going into the adhesive as it polymerases, it will diffuse into the air abraded adhesive layer of your, bio base. And then that will make actual covalent bonds, from your bio base to your cement layer to the intact little surface of your only. And those things are around 40 mega pascals. And like I say, we've never had a Debond, one of those composite models. But the ceramic, if it gets too thin, then the silicon starts to get flexed and it does not hold up as well. And you will have debonds with ceramic for a composite you might get wear, but you will not get a debond of the enamel replacement of your only. So we've talked about a few concepts and obviously this is nerdy stuff for most dinners, but when you talk to somebody like Stan Wendt, then it's important to recognize that science is establish these ideas, these concepts, and allows us to now connect the tooth top to bottom, side to side, front to back, so that it acts like a tooth. But the wear on the tooth that will act a little bit more like composite. But if you have ceramic, it acts more like ceramic, and a tooth is in between the ceramic and the composite. And so we're mimicking the tooth, but we're never getting it right about the same, unless you have gold for your onlay gold for your overlay, then that two body wear mimics the tooth better. But the, the bond is a little weaker to gold, but still, you can bond gold on these two bio bases with two materials that we recommend, one from Kuraray called Alloy Primer. You do need air abrasion to have that work. And the other product is from Tokoyama which is called Metal Tight. And both of those materials allow a covalent bond to gold, to the adhesive to the bio base. And so until next time, get bonded, stay bonded.