A Tale of Two Teeth

Throughout dental school and into his early career, Dr. David Alleman had a tooth with an occlusal amalgam that experienced intermittent pain on biting. The tooth was examined, but no cause for the symptom was found. Years later, after thoroughly studying adhesive dentistry, Dr. Alleman understood that there must be a crack in the tooth. Having recently acquired an intraoral camera in his office, he could now visualize the crack and, with the help of his assistants, dissect the crack and restore the tooth himself. The symptoms resolved and the tooth is still healthy and functioning to this day.

A few years after restoring the first tooth, the tooth directly above it chipped. Dr. Alleman assumed the chip was only in the enamel because the tooth was asymptomatic, so he thought further treatment could wait. But in 2011, to his regret, the tooth fractured through the root and had to be extracted. This unfortunate incident taught Dr. Alleman a valuable lesson about the urgency and importance of timely and accurate crack diagnosis, which he now teaches to his colleagues and students.

Both teeth had vertical cracks. One tooth was saved with proper diagnosis and treatment, but the other was not. This happens to patients every day, but understanding how cracks in teeth propagate and how cracks are treated outside the field of dentistry [engineering] can significantly contribute to saving more teeth. This knowledge empowers us as dental professionals and students, motivating us to learn more and improve our practices.

Articles discussed in this episode:

• Abbott P, Leow N. Predictable management of cracked teeth with reversible pulpitis. Australian Dent J. 2009; 54:306-315.
• Brannstrom M. The hydrodynamic theory of dentinal pain: sensation in preparations, caries, and the dentinal crack syndrome. Journal of Endodontics. 1986;12(10)-453-457

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Transcript

0:33

All right, here we go. Episode ten. Today we're going to talk about cracks. And we're going to talk about what a natural tooth has as far as cracks and cracks defenses, and what a biomimetic restoration has as far as cracks and crack defenses in the paper are going to highlight. We mentioned that in episode nine. This is episode ten, this is Abbott and Leow and this is the clinical trial that has established crack dissection as the most effective way to treat a cracked tooth. When I was a traditional dentist, cracks became a big part of my practice. After ten years, I started to have fillings break, teeth break like crowns would break, and often the crowns. If they'd had root canals, the whole root would break and the tooth would be lost. So those types of failures are usually called catastrophic failures. If you have a piece of the tooth break off and you repair the tooth, or you have a restoration placed, it's usually a larger restoration. So a broken tooth under a filling will become a crown. And then quite often if a crown broke off, then you would have a root canal at the at the least. But the root canal treatment required some way to connect the root to the restoration. And so that's a buildup. And the buildup was placed with a post. So in dental school I learned how to put posts into roots that would retain the buildup that would retain the crown. This is traditional prosthodontic protocols, but as I did that in my first ten years of practice, at about year ten people would come in with the crowns in their hands or the root in their hand, or they would say, my crown is loose. And what really had happened is the root had fractured and now the tooth had to be extracted. So these types of failures became very depressing to me. And I knew that if I kept doing what I was doing, I would have the same results in another ten years. But I would be even more unhappy because my first ten years, I had the myth that I was going to be successfully restoring these teeth long term. And so this idea of doing the same thing and expecting different results, you know, that's the definition of insanity that I think Einstein said. But the idea is that in dentistry, if we keep doing the same thing, we're going to have the same results. So every dentist is considering getting training in the six lessons in the biomimetic approach should say, am I happy with the results that I'm having of these cases that I've treated? The happiness for me came when a case a tooth was treated, and in five years it was still doing fine. And then in ten years was it doing fine. And now with the biomimetic protocols, we have 15 and 20 year and even more than 20 year successes. And in Japan they have similar success rates, depending on if the tooth is vital or non vital. And this idea of managing cracks in teeth and how they relate to cracks into restored teeth. This is a continuum of small problems to teeth that are lost from these cracks in the crack propagation. But the real progress for me, the real breakthrough was in January 2000. I bought a microscope. 25 years ago, I had upgraded my magnification when I started to do adhesive dentistry to a 4.5 magnification, and that was a real eye opener. I'm seeing things that I couldn't see decay using caries detecting dye was very easy to distinguish a pink from a red from a no stain, even in a deep area with 4.5. But when I went to six with the microscope, that was like another level of being able to see things. But I also was able to visualize these cracks at different stages of progression. And these cracks that can take a tooth out, always start small. Originally, when I would have a patient who had had a tooth that had pain on biting, the diagnosis that I would make was cracked Tooth syndrome. And what I was taught in dental school, the treatment was full coverage. So I would do a full coverage crown on this tooth and the symptoms would usually improve. But then quite often five years later, the patient would come in with that crown in their hand. And if you looked inside the crown, their tooth was inside the crown. And the only thing that I could think of when that happened. Wow, Cindy, you really bit on something really hard. In other words, my whole idea of a tooth breaking off is like one episode of tremendous force taking the whole thing out. I mean, I just didn't understand crack initiation. I didn't understand crack propagation. I didn't understand catastrophic failure. All these things I just had no clue. In dental school, I was not introduced to cracks in any shape, way or form. But I had a personal experience in dental school. I had a tooth that had pain on biting. The diagnosis in those days was pain on biting. You should put a crown on it. This tooth had, you know, clues. The amalgam, the isthmus width was about 1.5 to 2mm, just a small occlusal filling that had been done ten years previous. When I was 18 years old. And now this is my senior year of dental school. I'm 27 years old. It's a repeatable symptom. Everybody looks at it with their flaw and their 2.5 loops and with a mirror. Then they take an X-ray. They don't see anything. I have the symptom, but they don't see anything. Usually if you had crack tooth syndrome that was treated, you'd see a discoloration around a filling or a chip around a filling. You know, I had had a few patients like that in dental school. They really didn't want to call it crack tooth syndrome, because it wasn't every time I it hurt a lot. It's just a transient pain. So nothing got done in dental school. And then over the years, sometimes it would hurt, sometimes it wouldn't. Same thing. Take an X-ray. No decay. You can't see a crack that's in this plane through an X-ray. Sometimes a little bit. If it's really wide. But anyway, there's a whole series. But this goes on for another decade. And then even into the second decade after dental school. So now I'm into adhesive dentistry, and I am diagnosing myself because I know Martin Brannstrom’s work that we talked about last episode and Brannstrom with the crack tooth syndrome is more sophisticated and said, do you have pain on cold? So not only biting but cold indicates that we have a communication. The fluid is moving in and out and that's causing the pain. So it's the the theory of the movement of palpable fluid was first called the hydrodynamic theory. Now we call it the hydrodynamic source because we've actually identified the nociceptors, flagella that actually pick up the pain. That was work of Charlie Cox that nobody knows about. But anyway, I'm in my office. I know what I do, I've got practice and now I have a intraoral camera. I look at my teeth and I see a crack on the marginal Ridge. So the peripheral fracture that we talked about last week, I see it on my intraoral camera. Okay, man. Let's go. I've got a crack in to dentin. So I have my assistant bring me my anesthesia. I give myself the shot, put my rubber damn on. My assistants are cracking up. They're dying. So, under rubber dam and with the intraoral camera, I'm able to, identify a vertical crack. I dissect the crack, proceed to with air abrasion, do my immediate dentin sealing, resin coating bio base. Take an impression. Make an onlay outside the mouth. The next day, I came back. Cemented. the only it's still there. So 20 years ago, I dissected a crack, successfully cemented the onlay. This was the same thing that I was teaching other dentists to do. Because when I got my microscope, I could see the cracks. If they went horizontally, a part of the tooth would come out. But if they went vertically, the tooth would be lost or the pulp would be dead, because that vertical isn't going to miss the pulp, it's going to hit the pulp. Okay, so everything's good until, 2010, 2011 I start speaking for Kuraray and I'm on the road a lot onlay on. The bottom is doing great. I have a piece of the top chip off now. I didn't look at it very carefully because I'm on the road. I just put a little composite up there, put a light on it, don't get food impaction. I just keep doing my thing. No pain up there. It doesn't hurt my diagnosis at that time was I've got a fracture of enamel. Well, fracture enamel happens when a crack from enamel goes to the edge and then the crack is deflected. The rest of the enamel is cracked in it, delaminates. So that's what we call a clinical failure or something that is not biologically taxing to the tooth. That was a misdiagnosis because a year later a large piece of my tooth broke off and that tooth is now not in my head. There was a fracture vertically down the the mesial buccal root, and the tooth was lost. What happens? Well, in dental school we did learn of a neurologic phenomena called referred pain. The nerve that gives feeling to your teeth and to your eyes, called the trigeminal nerve. Trigeminal is mean. There's three bodies. The three first body goes to the eye area. The second body goes to the maxilla. The third body goes to the mandible. So this trigeminal nerve is the largest of the cranial nerves. But what happens is that this pain that goes back to this one body, that's called the trigeminal body in the skull is it goes to the brain. It gets a little bit confused. In other words, you can have these three major branches and they have branches that go into each tooth or into the eyelid into the eyeball. If you get pain here, when it gets back to the skull, into that trigeminal body, you can get pain crossing. And the brain interprets that as pain from the top, but it's really coming from the bottom or vice versa. Pain from the bottom can really be coming from the top. So that's called referred pain. It's a very well known phenomena in medicine. And anatomically it's related to this trigeminal nerve. When this tooth was lost, you know, I said That's interesting because I always had this over these 15 years, these symptoms that are coming and going. And Martin Brannstrom described that in 1982. He said, well, you get the crack started. But then you have a little bit of mineralization happening that impedes the movement of the fluid in the tubules. And also you have what's called secondary dentin into the pulp chamber. And so the actual distance increases and these attenuate or even eliminate the pain in many patients. And so the symptoms you're really looking for is not a consistent pain but a recurring pain. Now, when I read that 1982 and then related it to my own experience, having a successful treatment in 2005 and an unsuccessful failure seven years later, all of these things become very personal. I lost the tooth because nobody could diagnose even myself the referred pain. I fixed one, but in reality I had two vertical cracks right on top of each other because that's the place that I like to chew. You know, ever since you're six years old, you find most patients two more on one side of the mouth than the other. Some people, chew on both sides equally, but I was a right side chewer. I like to crush things. I like to eat an ice or nuts on the right side. But that force of occlusion is distributed first through the enamel. The enamel has a way to relieve that stress so that it doesn't go into the vital part of the tooth. And that's called enamel fractures. Enamel fractures actually are quite complex. It's not a straight line, you know, you go let me as just go from the DEJ out to the surface in the odontoblasts, go from the DEJ down to the pulp and they stay there. I mean, that's what you learn. It's a basic but this is what's really happening. And it's like music, the finest music weaves different parts and is going in different directions. And so this is called a decussation. And so a decussation, this woven enamel gives it the ability with great difficulty to get fractured. But if it does fracture these decussation again move the fractures and then they get to this massive area of the DEJ which is these inversions of enamel and these investigations of death that have this interphase. And all of a sudden these fractures in enamel get diverted. And so the fracture in enamel usually stays in enamel stops at the DEJ. That's the biomimetic way to, to deal with functional stresses. And you're always going to be chewing on your teeth. But how those forces get dissipated. First, there's a little bit of movement, expansion of these enamel. What we call rods. But really they're these decussated layers. And this little expansion is about 3 or 4 microns. All the rods just shift a little bit. If you destroy the middle of the tooth, which we called the Rainey ridges last time, these subocclusal oblique transverse ridges. Then all of a sudden, instead of going three microns, every time a tooth is chewed on, we get 175 microns. Separation of the tooth from the restoration. Remember a bacteria is 1 to 3 microns. These vibrations of these small little movements, nothing is separated, is just absorbing and distributing the stress. But the stress distribution of the whole tooth comes in the bottom. And that bottom part we call the bio rim. And that's the area where we actually have forces from enamel that usually go down now as it conjoins with the dentin. The dentin kind of expands a little bit like this. So this is called isotropic movement. It's expansion. The top movement is called anisotropic. It only goes in one direction. The isotropic movement expands. And this is really miraculous. We do this a million times a year. We don't think about it at all. But when we do it the forces have to go somewhere and those forces in a natural tooth are distributed. And if we get a lot of force, then we can have these small little, areas that that fail, at the bottom of the tooth. This decussation is not tied into the dentin. very well, because it's so thin. And that's the place where an abstraction lesion starts. But the idea is that when we're trying to mimic something in nature, we're always going to be, if we're smart, really humbled by the idea of even coming close. It's not a duplication of nature. We're just trying to get close that have some ideas that make the tooth act like a tooth. So in the year 2000, I got my microscope. I'm learning about cracks. I'm seeing major cracks. I'm relating that to my failures that I've had in my, clinical practice in the, in the previous 20 years. And all of a sudden, I'm saying I need to know more about cracks. And so I happen to have a good friend who's a crack expert, and his cracks are on airplanes, mostly airplane wings. And so I said, Dennis, I said, you're a smart guy. You're an engineer, you're fixing these $2 billion stealth bombers, that Hill Air Force Base. What do you do with cracks? He says, well, first we have to find them. So we have detailed inspections regularly. And these scans of the airplane, these stealth bombers are all made out of carbon fiber Ribbond composite. It's very similar. I asked him if you'd ever heard of a leno weave. He says, oh, yeah, he brought over a book he show. This is what, a leno weave. It's it's you know. And then we started talking more about cracks in general. He said, well, you know, the skin. Where are you going to bond over it. That's important. But what do you do with a crack under the skin? He says, well, you have to take it out. How do you do it? He says, well, I take a big drill bigger than the than the crack. And then it has around in on it, and I just go down and look at a microscope and see if the cracks gone. If it's not, then you drill a little more and then look at it. And then the bonding procedure inside is, basically, a bonding procedure that we're all familiar with because these, resin molecules, they all originated with the idea of the epoxy resins that were invented by Castan in 1936. So all of the chemistry is some variation of epoxy. First, you start out with a slow cure chemical cure, and then you can go to the like your systems anyway, very, very similar to fixing teeth. And so Dennis and I would talk when we were playing golf about fixing teeth, fixing airplanes. But the idea is that these cracks in a natural tooth are confined to dentin and stop the DEJ. But if a crack goes past that, under prolonged forces accumulating and fracturing, these these failsafe mechanisms that are in the natural tooth, if it goes, then you feel it. And that's Brannstrom and that's the system telling you you've got a bigger problem. You don't have these little problems, you got a bigger problem. And that's the pain that's coming in to the trigeminal nerve. And all of a sudden that pain on biting says this tooth is not acting like a normal tooth. And that's a highway for infection. And this is what kills pulps Now some pulps die. Very dramatic death. Other pulps die slowly. I was having symptoms on two teeth. The top tooth died a slow death. Never had a major toothache. But I lost that to the small symptoms on the bottom. Were diagnosed and treated correctly. And that's the success of a diagnosis. early and an early treatment where we're reconnecting the two side to side, front to back and top to bottom. And that's connection. Side to side is in the outside layers, not in the inside. The a natural tooth. We don't have a connection in the pulp area. That's a very soft material. But the connection side to side is coming through a 360 degree connection around the tooth. Graeme Milicich likes to make the analogy of a compression dome. A dome doesn't have middle connections, it has side connections and the top compression on the solid side foundations make it function in that. That way, in the six lessons approach, we always say a crack into enamel is biomimetic. It's the way the tooth designed a crack into dentin is not biomimetic and needs to be treated. This paper in 2009 treated these cracks by dissecting the cracks, the same as my friend Dennis Groh would dissect a crack on a, B2 bomber. And the two endodontists who wrote this paper. Abbott and Leow had symptomatic teeth that they tested the pulp. It had a vital test, but then they dissected the crack and then restored not with the sophisticated bonding system, even. They just restore to the glass ionomer And they had a 95% success rate. Other approaches to cracks were you bond over the reported success rates are in the 30s or 40s, maybe 50%. So this is a significant difference. Of course, the glass ionomer restoration of the dissected crack didn't hold up under function. Something had to be done so that it would have a functional stability, but it proved the point of dissection. Now, I wish I would have known this paper, you know, in dental school, but of course I didn't. I had to figure it out myself with the help of engineers. But now we have in our own practice based research network, 20 years of experience teaching and performing crack dissections and successfully treating teeth that have had back dissections with advanced adhesive techniques of deep marginalization, immediate and sealing semi direct techniques for enamel replacements. But that's the idea. Is that cracks in enamel that's biomimetic stress relief vaccine to dentin or a pathology can kill the pulp with infection or take the tooth out with a vertical root fracture. So until next time for number 11, get bonded, stay bonded.