What is Minimally Invasive Dentistry?

Biomimetic restorative dentistry has been taught and practiced for over 20 years, with its roots linked to minimally invasive dentistry that started decades earlier. Minimally invasive dentistry sought to conserve tooth structure and restore only parts of the tooth affected by pathologies. 

With the invention of adhesive materials, adhesive dentistry showed promise in advancing minimally invasive principles with new materials that no longer required retention, but the adhesive restorations still fell short. Teeth are more complex than many other materials that are adhesively connected, so simply bonding the restoration to the tooth did not yield long-term success.

In this episode Dr. David Alleman discusses how minimally invasive dentistry paved the way for the more conservative approaches we use today, how biomimetic dentistry made adhesives more predictable, allowing for longer-lasting bonds, and where cosmetic dentistry fits in to the adhesive dentistry spectrum.

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Transcript

0:33

Welcome to season three of the Six Lessons Approach podcast. So our topic today is what is the definition of biomimetic restorative dentistry. How does it differ from minimally invasive dentistry or adhesive dentistry or cosmetic dentistry? Any dentist in private practice has the options to do many types of dentistry, and the definitions are aren't as important. But in the world of biomimetic dentistry, there's been some leaders and the leaders agree on some very basic concepts. And these basic concepts overlap with the other ideas of minimally invasive or cosmetic dentistry or adhesive dentistry. So let's start with the one that I would say is probably the oldest. And that's minimally invasive dentistry. The idea of minimally invasive dentistry was the less tooth that you cut down, the better it is for the tooth. And so there was a dentist named Miles Markley. And Miles Markley lived in Colorado, the state adjoining Utah. I didn't have the opportunity to know and meet Miles Markley personally, but I read his articles that were published mostly in the journal Operative Dentistry. And he in his day, which was the 40s and 50s, saw a lot of deep calcification and early lesions. Carious lesions on patients that basically didn't brush and your teeth or floss their teeth. In other words, everybody had class II inter Proximal decay because no one was really that careful with oral hygiene. But this minimally invasive approach on incipient lesions, small lesions inter proximately made a lot of sense. And he developed instruments that would allow him to make very narrow slot preps and instruments that would allow him to condense amalgam and gold foil and other minimally invasive material into these very tiny, preps that would deal with these very tiny, incipient lesions of calcification and early decay. In those situations, Miles Markley was using the materials that did not shrink. Now, amalgam doesn't shrink. It actually expands a little bit. Gold doesn't shrink or expand. So it's a little bit better that way. As far as stressing the remaining two structure. But gold has some downsides. It costs a lot more and it's a very difficult material to manipulate. I don't think any I don't think any dentist learning in dental schools today learned, direct gold foil techniques, which I was trained in and one of my mentors, Fletcher Craig, was a master of all Masters of gold foil restorations. He had one advantage. He was ambidextrous so he could take a Wedelstadt and go here, and then Wedelstadt here and he never have to change his position on his on his chair. but gold foil had its day had a lot of success and direct foil. Could it be used in class two restorations? Myles Markley did that taught that, the Tucker Study Club, was in conjunction with Myles Markley philosophy of minimally invasive dentistry. But then, we had the idea that what do you do when you have something that's a little larger and a broken cusp or a fractured tooth? Restoration that had decay sometimes would need to have some type of retention form. And so Myles Markley actually pioneered what was called a cemented pin because retention form of replacing material that's, cusp has been lost. If you put one pin in and then use that pin to retain, give the resistance form, retention form, to the restoration. That was a good, technique. The most popular pin was a screw pin called a mini pin. Unfortunately, that had the disadvantage of putting stress into the two structure that the pin was being screwed into, and that would cause a little strain and even fracture of that two structure. The man researcher who research that was named Angelo Caputo and Doctor Caputo was at UCLA, did some great studies with thermoplastic stress and strain, testing of screw pins. Myles Markley solution of a cement pin didn't have those disadvantages, but the fatiguing of the cement, also had a disadvantage. Anyway, there were many things that this minimally invasive approach using amalgam and gold, had advantage. You didn't cut a tooth down for a full crown as soon, if you had a failure long term of a minimally invasive restorations, then you could have something that, perhaps would, go for a decade without having a, a full coverage crown or a partial coverage crown, which was another aspect of minimally invasive dentistry. And I learned that at University Pacific from my Crown and Bridge instructors. We learned how to do three quarter crowns with very precise retainer grooves. We learned how to do 7/8, gold lingual, veneers, that had pin ledges. I mean, these were very precise preparations. Many dentists didn't have the hands and the eyes skills to do that. My me personally, I got an A in these techniques because my hand ice skills were way above average. But in reality, once a PFM, came out, then the idea of saving facial to structure to make it look like a tooth while restoring a or adding to the lingual part of a tooth that was fractured on a molar. These three quarter, 7 or 8 crowns have been lost basically to the profession. They're not even, taught in dental schools, but it was another aspect of minimally invasive dentistry. Very prominent teacher named Lindsey. Pankey the Pankey Institute, the doctor, Lindsey Pankey now obviously utilized for replacing teeth, these ideas of partial coverage, model, on leis those types of preparations in the 30s, 40s, 50s were the most minimally invasive way to save teeth that, otherwise would have to have a full coverage and the full coverage in gold was never esthetically really pleasing to most patients. So once in the early 60s, the PFM came on the market, then all of a sudden, the minimally invasive ideas lost the popularity and dentists were just cutting teeth down, removing all the enamel and replacing it with porcelain, which had some esthetic advantages. But long term it could be very, static. But, the idea of adhesive dentistry coming into the profession after minimally invasive dentistry was replaced by full coverage porcelain fuzed to metal techniques, it was kind of a breath of fresh air. And the potential of having a restoration only partially restoring, partially missing two structure became very, attractive. But the problem was, is that the minimally invasive idea which created techniques are preparations that had high, ratio of bonded to unbonded surfaces for an adhesive approach became even worse than the minimally invasive preparation using amalgam or gold foil. And why was that? And the reason why is that amalgam and gold foil did not shrink. And so if you have a small cavity and then you make a small preparation because you only have, some incipient decay, then if you tried to use an adhesive material that was methacrylate based, which all of the composite materials now are methacrylate based, some of the amide based, adhesives and materials are starting to show some promise. But the difference at that time gave the advantage to a material that was developed, in England. And once it was developed in England, it was actually sold to a company in Japan. And so the glass ionic cements that were developed in England for minimally invasive dentistry and actually perfected with GCs purchase of that patent, and became very popular around the world in these minimally invasive preparations and the middle of basic preparation, usually made with a small bur or a fine diamond, still retain the basic structure of the tooth. And so the tooth was supporting the restoration. In minimally invasive dentistry, if you use a glass eye ornament in those small preparations, they would still work as well as amalgam or as gold foil. The problem is they did not have a high bond strength, but they didn't shrink in a way that would cause micro leakage, immediately. So glass ionomers were very good on these small preparations. The best technique that was developed in the late 60s might have been developed in the late 50s, but only, available to the market in the 60s was an air abrasion unit that was developed by Doctor Black in Texas. And Doctor Black in Texas inspired a young dentist, who was a little bit, Disgruntled or unsatisfied with the idea that just chomping apart a cute tooth with a high speed turbine was a good idea. Tim Rainey, good friend of mine, still with us. Tim Rainey, when he saw as a student what a high speed turbine with a coarse diamond could do to a tooth. Intrinsically, he felt like that is not good for the tooth. And as these full coverage PFM crowns started to fail, he became more and more convinced that the destruction of the enamel was the beginning of the end for most teeth. And so he's a dental student. In the late 60s, he comes to these feelings kind of, a gut feeling this is not the best thing to do. And he came across Doctor Black. They were both from Texas. And when he saw that Doctor Black had this new way of not ripping apart a tooth with a, high speed turbine. He got intrigued by it, and he didn't know exactly how to get it because it wasn't available in the market. these air abrasion units didn't have the ability to cut enamel quickly. So definitely it wasn't for making crowns, but it's also for making preparations that traditionally needed a certain width, a certain depth to, achieve the GV black standards for retention form and resistance form. But again, the C factor is always high in these small preparations. So if you have adhesive dentistry either with glass ionomer or with the shrinking, methacrylate based composites that are stronger, more durable, but have a different pattern of shrinking the glass ionomer when it shrinks, it shrinks. It has micro cracks throughout the whole composite restoration of the whole glass ionomer restoration in a methacrylate based composite it the shrinkage goes towards the middle and the stress or the fracture will be at the interface of the tooth. And so that creates the micro leakage. It's a stronger material, but the leakage to the tooth between the restoration of the tooth happens more quickly. So glass ionomers were good and still are good on minimally invasive preparations, especially with air abrasion, but they're not as good in larger preparations where now the support of the restoration has to come from the connection of the restoration to the tooth. And that leads us to the next concept of adhesive dentistry. So when adhesive dentistry came, all of a sudden we had the ability to glue things on to teeth. Now the gluing process is very complicated, but it has a, ability that in our own minds we can think of things that get glued together. Everybody's glued. Something with Elmer's glue. If you have a fractured ceramic dish, Elmer's glue can help. If you have a fractured plastic dish, we have the ability to use super glues and all of these ideas that if you could just glue the restoration onto the tooth, you know that would be a great thing because it would be minimally invasive. You're not cutting the tooth down, in a crown preparation or making big holes for to hold your restoration. But again, it's connected to the tooth. But the connection is really where the details, have to be understood that that connection has to have a certain strength. And so these adhesive materials have started to come into the market in the 80s. And I was a young practicing dentist when this first happened. Then many products came to market that said, this bonds to enamel and it bonds to dentin. Well, bonding to enamel was known without what are called dental primers. And so the dental bonding systems, the first one that really works comes out in Japan in the late 70s. That was after I graduated from dental school. And course it was. Japan only marketed there really didn't get marketed in the United States until the early 90s, but the idea of bonding in a situation that was flat versus bonding to a situation which most preparations removing decay would be, which would be a more shape of a cup or a bowl instead of a plate. If you have a flat surface. It was not known that the shape of the cavity immensely changed the amount of strength of the bond, and that was only discovered in the mid 80s. And so for a decade, the adhesive products were not taking into consideration the shape of the cavity. And that became a problem in certain situations with certain materials. And those problems were problems that I suffered through personally because I did not understand the different materials that were being produced. I did not understand the chemistry. I did not understand how small the gaps were that could cause a reinfection from bacteria. But as us this started to come out. It was all related to the free radical polymerization reactions that were the foundation of these methacrylate based adhesive products. you know, I happened to get an A in organic chemistry, in my undergraduate students years. Only the only reason, because I was afraid I wasn't smart enough to be a dentist. And so I, I knew organic chemistry was going to be a, a green light for most dental schools. And so I really put my mind to it probably the first time my life to really try to study something in seriousness. And the free radical polymerization reactions, which are the foundation of any plastics that you have epoxy resin, is, you know, still used around the world. It has the ability to take something that's not in a shape, and you can put it into any shape, and then you can get it to become hard. But that is always at a cost of, if the surface is clean and dry and also if you have, enough time for the polymerization to happen, epoxies usually take about five minutes, to polymerize, but they also don't do well in moisture. In other words, you read something that says you want to glue your superglue or your or your, gorilla glue. It will always say have a clean and dry surface. so we have a challenge when bonding to a vital tooth that it's moist. And now the shape of the cavity has now given us a situation where there's a competition between the different sides of a cavity preparation. The different walls will have different characteristics. And that is, describe in, I believe, season one, many of the episodes I've talked about see factor in hierarchy of bond ability and decoupling with time. These proprietary concepts that I had to invent and understand before I could really get 100% success in every adhesive procedure that I did. You can go back and review those, but they're very important because minimally invasive dentistry and biomimetic dentistry, there was a bridge called adhesive dentistry that worked on flat preparations such as a veneer preparation. And so veneer preparations became all of the rage in the 80s, 90s, even today, cosmetic dentistry, everybody's going to want to have thin layers of ceramic on your teeth. It'll only cost you $70,000, you know? I mean, less in Utah. But, you know, it's, elite type of Hollywood type of, procedure that, you know, vanity kicks into it. I mean, there's nothing I mean, But the idea is that if my teeth look like this, for most people looking to what? Have a girlfriend, have a wife, talk to children or grandchildren is like, these teeth gonna look like grandpa's got some teeth. That's usually a good thing, you know, to score some points. But I don't need to look like Burt Reynolds. I can't even know if nobody knows who Burt Reynolds is anymore, who Brad Pitt is. He's still around Brad Pitt, I guess, you know, who's, the whatever is on TV or, the movies. You're probably seeing ceramic veneers. I get that, and, you know, if that's your demographic in your patient base, more power to you. And, you know, we can refer you to Matt Nejad any time you'll do the best veneers in the world. And he does a great job. But most people just need their teeth so they can pretty much look pretty good and basically eat better. And that's where the biomimetic concepts depart from the cosmetic concepts. Now every biomimetic dentistry or train does some cosmetic dentistry. It's just what's the percentage and how detailed and how artistic does a ceramic need to be? If you're looking from three feet versus three inches, you know the movie cameras right there, three inches from your teeth, you can see everything in it. You know, that's a reality in some art forms, movie and television. But the idea is that you need to understand that cosmetic dentistry, although it's still popular in many parts of the world, obviously, for most dentists, it's maybe 20% of their practice high end, most dentists that I've trained over the last 20 years when I always say how many teeth you restore in the back compared to the teeth you restore in the front, the answer is always 8 to 1 or 9 to 1. I restore nine teeth in the back for every one tooth I restore in the front. If your practice is different, it's different. You know, you, you you market to the the market that you have and you try to satisfy their desires. But this cosmetic dentistry, I have nothing bad to say about it. All I'm saying in my practice and 40 years in Utah, it's been about maybe 10% of my of my practice. But the kind of cosmetic dentistry I can do usually can be done with a much simpler and less expensive approach of using composite rather than ceramic veneers. Composite veneers are very, very important and we have some good masters, some excellent masters around the world. all of those things. They are minimally invasive and adhesive, but they don't need the stress reduction that we have is a definition of biomimetic restorative dentistry. And so as we evolve from minimally invasive to adhesive to cosmetic dentistry and now biomimetic dentistry, it's really, the best of both worlds. You have all of those opportunities in minimally invasive, procedures, in cosmetic procedures. And now you can treat any type of missing two structure using the same protocols. You don't really need to to adjust them. The only difference is that you might have a decoupling period of 30 minutes versus five minutes in a deep margin elevation, another topic of of earlier, earlier episodes. and then next time we'll go a deep dive into each of those those four types of dentistry that have adhesive aspects of them. to, give you more information of the six lessons approach to biomimetic restorative dentistry. Till next time. Get bonded, stay bonded.