The Difference Five Minutes Make: Decoupling with Time

Each lesson in the Six Lessons Approach to Biomimetic Dentistry (SLA) is essential to restoring a tooth in a way that stays bonded and symptom-free. These two failings of traditional techniques — debonded restoration and post-operative sensitivity — are addressed in each lesson, but when it came to the bonding stage of the restoration, Dr. David Alleman was able to reach a pivotal conclusion from the published research.

Different parts of the tooth form hybrid layers at different rates based on the amount of hydroxyapatite. Composite will shrink to the best possible bonding surface, potentially leaving gaps in areas that have weaker bond potential. Understanding how to overcome these two variables is key to creating a restoration that bonds the tooth side to side, front to back and top to bottom like a natural tooth. This biomimetic bond eliminates gaps under restorations that cause post-operative sensitivity, but it requires understanding how bonding systems, composite and dentin need to work together within the first five minutes of the polymerization process. Dr. David Alleman named this process decoupling with time.

Articles referenced in this episode:

• 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

Welcome to the Six Lessons podcast, episode three. So today we're going to talk a little bit about the interaction of the six lessons. Because there's never one lesson that is that's all you have to do. That's why there's six lessons. There's actually six ways to make it to hurt. If you fix it. But if you don't fix it in a way that connects it side to side, front to back and top to bottom, then you can have pain and the pain are two sources. One if you lose the hybrid layer, then you have a gap underneath the restoration where the hybrid layer has been disrupted, and that gap fills up with fluid pulpal fluid. So you can have a sealed restoration on both sides, but then you can have a gap under the restorations. Fill the pulpal fluid. And when you chew on the restoration the pulpal fluid is pushed towards the pulp. So that's the hydrodynamic source of pain. It was theorized by Martin Brannstrom in 1982. In his book in 1986 is a great article on cracked two syndrome, but cracked teeth and gaps underneath restorations that cause pulpal fluid to move towards the pulp under mastication. Those are the sources of pain on biting that patients feel. And so the idea of strength in the hybrid layer as the greatest contribution to comfortable dentistry, and then the dissection of cracks, is the second greatest contribution to keeping teeth pain free and or function. And then of course, occlusion, which is less than six. You had to adjust the occlusion so that it's in harmony with the other teeth as they bite down. And there's not one tooth getting more pressure into the PDL, which can be very painful if you have a tooth in hyper occlusion. But the idea of less than one with caries less than two with cracks, less than three with the hybrid layer, and then less, and for these give us the ability to make sure that the seal at the bottom of our at bottom of restoration is perfect. And so we will know that because there will not be fluid trapped underneath the restoration that maybe seal on both sides, but now it has that gap underneath the restoration after polymerization. And so the hybrid layer formation, which we talk about in detail, lesson three is at risk of the polymerization stresses that can be generated in lesson four. And so the connection between lesson two which is crack dissection. And lesson three and four is that you now have introduced a preparation that instead of being flat like a plate or even curved like a bowl, is now like a really narrow cup. But the idea is that if you have that, then the C factor, which is the ratio of bonded unbounded surfaces, if you would both fill a restoration and become so high that you're guaranteed to lose a bonds that has been tried to be established, but now is losing in its competition with other areas of the preparation that are bonding more quickly. And so these narrow preps that are the result of a dissected crack, these are a situation that are special to the six lessons, because we create now a potential problem by removing a real problem. So the risk and reward and the reward of taking out the crack is that now you have the ability to stop the movement of possible fluid from cracks opening and closing. But now you have the risk of creating a gap when you try to restore this high C factor dissection, or what we sometimes call a trench. How do you do that? I have an answer for you. It's called decoupling with time. Now, anybody that's followed my Instagram for the last five years, the idea is that this is science, and my approach in Instagram is to introduce everyone to the science. But Instagram hasn't been created to teach you the six lessons in the reality I am teaching professionally. I've been doing that for 20 years, actually 22 years. And so the teaching has been systematized. I have a system for teaching, and it covers all sorts of defects from decay, fracture and trauma to the teeth. And so it does everything you need, but you have to learn it that certain things are more important and can't be compromised all the way to occlusion, which occlusal adjustment is known by. Every dentist. And every dentist that has sensitivity or pain does an occlusal adjustment, thinking that that will be something that will help. It can, but it has to be understood. What is the source of pain? What is the source of dental failures? I think that was our first episode in season two. What is the source of failure? Well, infections and gaps. And then we talked about how the cracks can propagate and become catastrophic. But then we talk about in lesson four and lesson two, the dissection of the cracks. And then we deal with these high C factor preparations when we do disrupt the cracks. And this is how we do it. We do immediate didn't clean on all the walls. The immediate dentin sealing that we do on all the walls will be with a gold standard bonding system, a gold standard bonding system that is a self etch system. A mild self etch system needs to have the smear layer that's been created in the preparation, which is just chopped up. Then as you're dissecting the crack, that smear layer needs to be removed or thinned. And that's called a conditioning step. Fusayama’s conditioning step that he innovated in 1980s and published in his book in 1993, again, was phosphoric acid etching. Phosphoric acid etching has that advantage that removes the smear layer, but it creates another problem solving one problem often creates another potential problem that was an inadequate infiltration of a hybrid layer, which could now be five microns thick. If you use a total etch and remove all of the hydroxyapatite from the outer layers of the hybrid layer, the symbol that we use, the Alleman center, has a symbolic meaning, as all symbols do. And this is there are different layers in the hybrid layer, and these different layers have no hydroxyapatite on the outer layer. Outer layer less hydroxyapatite removal on the next layer, which would mean more collagen is being covered with hydroxyapatite. And then this third layer is where the real rubber meets the road. A little bit of hydroxyapatite has been removed, allowing infiltration of the monomers, and when polymerized this becomes like that. So this is the hybrid layer connection and it's always less than a micron thick. These top layers can be three microns in thickness. Well if you have three microns here. But the only one that counts is a half micron. You want to make sure that this doesn't interfere with the infiltration here. And that's what a selfish gene system does. What it does is that it compresses all of these layers. So this outer layer where most of the hydroxyapatite is gone, is very, very thin. So maybe it's like 100 nanometers. And then the next layer where you still have collagen has been mineralized, but it's not mineralized totally like the outer layer. That might be another hundred nanometers in thickness. And so if the layer where the rubber meets the road is 500 nanometers in thickness, which is half a micron, then this layer is thicker than these two layers. Put together with this approach of this bonding system, which is a mild self bonding system. Now you may ask, but your hat has four layers, but you would never ask. The fourth layer here is actually dentin that has not been mineralized at all. Outer layer the most deep mineralization. Next let's do mineralization. Just a little bit of the earlier mineralization on the important part of the hybrid layer. And then this part no deep mineralization, only infiltration of hydrophilic monomers like HEMA like 10MDP and like water. And that water molecule obviously is the carrier or the solvent that brings these monomers into this sound dentin. And this sound then gets infiltrated through what are called microtubules. And, you know, everybody knows what a dental tubule is. It's one micron in thickness. But a micro tubular again isn't on the micron level. It's on the nanometer level which connects the tubules. Wasn't even very well understood in Fusayama’s days. But now that we know that 20% of dentin is water, that's not 2%. That's not a small number, that's 20% of dead is water, 30% is collagen, 50% hydroxyapatite enamel, 95% hydroxyapatite, and then 5% combination of water and a little bit of protein. But the idea is that now we have the ability to get underneath this important hybrid layer and make an area that's called a acid base resistant zone that has been nicknamed by Tagami in 2009, and he calls it super dentin. Simone Deliperi and I were in the audience at the International Association of Dental Research when 400 dentists heard this joke by Tagami because he knew that in 2009, super in the United States, no marketing person in the world would say this is super, because that's so 80s, right? In the 80s are like super this, super that. No, you would never say super. But the guy is very bright, very much above average. He knew what he was doing. He was playing with the audience because he took off his glasses and he said, and we have found this phenomena and we are going to call it a super dentin So the nice little endearing accent is super dentin, you know, and Simone, I look at each other like he's playing with us. He's joking. And the whole the whole audience was expecting some very scientific sounding phrase like acid base resistance zone. You know, to call it super dentin. I mean, it was it was beyond brilliant. It was funny. It's a memory that I've talked with the Junji about and, and he agrees that, you know, he was playing with the audience. He knew that a super was a passé term, but super dentin is with the self etching systems, the ability to make the hybrid layer not only resistant, totally resistant to low acid, but also totally resistant to high basic attacks. You can't dissolve this layer that is one even two microns thick. It can be very thick compared to these other layers, which are only a half a micron or a 10th of a micron. But this superiority of the formation of the hybrid layer is really what the science to me shows to be the most exciting, because you don't need to cause a problem with fluid being introduced to your bonding fields with these self etch low pH systems that create super dentin. Okay, so let's get back to our practical application. We've got a high C factor preparation. Looks like a cup. It looks like a really skinny cup. And so you're making your hybrid layer on the sides. But again it's only one micron above sound in and one micron below sound. And it's not thick at all. And so the sides once the hybrid layer is created there's no pulpal fluid coming in to the bonding field. We get a polymerization with the light. The polymerization with the light may be a little difficult because of the depth. So usually these deep cavities we we recommend higher light. Or if you want to get really sophisticated in your in your biomimetic techniques you can get a glass rod. I mean this is obviously not a glass rod. This is just the pan. But pretend like this was a glass rod. You're not going to use it as a post which it was created for. Because we don't use posts, we don't use pins in a biomimetic approach. But if you put this glass rod into the preparations, shine the light here. The light goes five six millimeters deep, which sometimes these dissections are five six millimeters deep, even deeper. But that polymerization with the light of the hybrid layer is done as a light, cure procedure. That hybrid layer now is starting to polymerize. That polymerization will only be decreased in strength if composite. That's thick enough to form a center of mass that can pull away from that hybrid layer weakens that hybrid layer. So what would be the best way to do that? Bulk fill this, I see prep, put the light on it. All of a sudden, parts of the hybrid layer would be weakened, stretched, or even destroyed. You know that's not what you do. Okay, so first you got your ideas and then you're going to put a half millimeter of flowable And when you put the half meter below the flowable, if that preparation is only three millimeters wide, then you can see that a half millimeter on each side takes away one millimeter of the distance between the two walls. So they're getting close together, but they're not connected. And more importantly, the bottom is not connected to the top, which may be the difference between root dentin or deep dentin, and superficial dentin which has a gradient of hydroxyapatite. And so you have that half millimeter and you get the light here. You put the light on again, you can put in a glass rod to get that light activating the half millimeter of resin coating more efficiently. That's a great technique, but at some point you're kind of limited if you put a layer of composite in. Now, even if it's a small increment of small size, you're going to be connecting the walls. And the Alleman-Deliperi rule is you do not connect walls of different layers of hydroxyapatite, which we call the hierarchy of vulnerability, for at least five minutes. So it's only taking you a minute and a half to put in the resin coating. So all you have to do is go do something else that's called decoupling by coffee break. Or you can take a photograph that's called decoupling with photography. But the idea is that you just let the maturation of the hybrid layer and the resin coating happen for five minutes before you start putting in a connecting layer of composite after the five minutes, then you layer the bottom with a small increment. We use Deli-bits which are 1.5 increments. Alle-bits are too big in this situation, so I recommend half of a Deli-bit, which would be 0.75mm. And as you push that in with the brush, you know it will connect the walls. But you're still going to be basically in the same hierarchy of vulnerability, the same deep dentin will be connecting to deep dentin. And then you like cure that again. You could use a light rod to help speed that up. And then the next layer would just be more superficial. Dentin. There really wouldn't be a difference of pull on both sides, but you've already waited the five minutes for your hybrid layer. And so these very difficult high C factors are just maintaining the maximization of their bond strength by waiting a period of time before the restoring composite starts connecting the walls and kicking in the forces that we call C factor forces. And you know, this science has been studied since 1987. So you're talking about we're getting close to 35 years, and that's 35 years has shown that this is something that if you neglect, you will lose half of your bond strength in any size of prep that you use. But if your prep is only enamel, that's a different situation. Your preps are hardly ever only enamel. That's called incipient dentistry. If your patient base is only incipient dentistry, you would probably be the only one in the world. But, you know, you're, you make your life easier. But as we work into these areas where we actually have deep decay or the areas where we actually have deep cracks that need to be dissected, or you're in areas that have deep boxes with different levels of the hierarchy, bond ability, then these tools of decoupling with time, fiber placement, limited volume, increments of composite in the restorative process. All of these work together to make it so no matter what challenge you're presented with, you have the tools to systematically approach that. But it all starts with the hybrid layer. And if you're using a self etch system, the superintendent. So, till next time, I think next time is episode four. We will see you get bonded, stay bonded. Always great talking to you.