Basics of Occlusion – PDP090

Jaz’s Introduction:

Hello, Protruserati, I’m Jaz Gulati and welcome back to the big episode I was telling you about this is the basics of occlusion carrying on from the the back to basics series in August, a lot of you messaged me with your occlusion questions, so I’m going to answer some of them today, but not in like a Q&A format. Because we’ve done that already in question 15 I’m just gonna take you through a journey, right? I’m gonna take you through a journey that’s going to be mirroring some of the things that I’ve picked up in my journey. And the point of this introduction is to just tell you that we are all in a different place, in our own respective journeys. So some of you may be listening and you might be a dental student, right? And you may be placing your first ever restoration tomorrow, let’s say and you are just thinking, Okay, when I stick that colored paper inside, articulating paper, and you get I get the patient to bite together, what are those dots going to look like? And you’re just like, that’s occlusion to you, right? When the patient bites together, how will it look, right? Whereas some of you may be beyond that. Some of you may be quite well versed in raising the occlusal vertical dimension, opening up bites, placing multiple units and multiple restorations at the same time and having some degree of control of the occlusion. So each individual is in a different place in their journey and the learning never stops. Now, if you are brand new to the world of occlusion. Welcome to deep dark world occlusion, I’m going to try and not confuse you too much. But try and give you a few things to think about. I’ll hopefully make sure that as you learn, right? It’s going to head you in the right direction. Because the thing with dentistry and the thing with occlusion is that sometimes the first time you learn something, right, it doesn’t really, really sink in until maybe a few years later, it’s happened to me so many times where a few years later, the same concept has been repeated and explained to me in a slightly different way. But the only thing that’s changed, I’ve gained more experience. And now that thing starts to make some sense. Now, if you are someone who’s very experienced some of the things that I might talk about saying this episode might offend you, okay? They might be against your occlusal religion, okay? But you know, my philosophy, right? Listen to everyone and do what feels right to you. So don’t take anything personally. Okay? These are just my views and opinions, some things that I’ve gained from my mentors. Now, just before we start the episode proper, a couple of shoutouts, haven’t been shoutouts in a while. Okay? Shout out to Afif who reached out to me on Instagram to say thank you, because he is Algerian, he’s a French speaking dentist, and he wants to be able to communicate dentistry in English, right? So he’s using my episode, right? Or my content to learn English and dentistry. And he said, Thank you for that. And I was like, well, that’s awesome, man. More power to you, Afif and also, thank you for the lovely message from Allah. Allah reached out to me on LinkedIn, to let me know that she was kind of in a stuck position. And then from the podcast, she found it very positive and uplifting, and therefore it helped her to reconnect, I don’t know how, but she said it helped her to reconnect with her principal and reconnect with dentistry again. So again, guys, messages like these really, really helped me to keep going. So thank you so much. I just want to do a little plug for the Dentinal Tubules Congress like wherever you are in the world right now, I hope you are safe. I hope you’re well. And the UK the COVID situation is, I guess, kind of improving to the extent that we’re now having in person dental education again. And usually my favorite event of the whole year is the Dentinal Tubules Congress. This year, it’s gonna be in Brighton, and that’s just three weeks away. So if you’re in the UK, and you haven’t booked yet, and you want to come to the dental event of the year, please check out the website dentinaltubules.com. Look at the Congress, look at the speakers. It’s just full of great memories for me every year, it’d be great to catch up if you’re coming. So this episode’s Protrusive Dental pearl, some of you may be listening for the first time, well, every episode I give a Protrusive Dental pearl. For the fellow Protruserati who always listen, here’s my pearl for today, right? So it’s all about canine guidance. And I know I’ve spoken about this concept before, but I’m just gonna make it into an official pearl. So now it’s official. Okay, when you observe canine guidance now because this is a back to basics episode, I’m going to actually describe canine guidance like some of you I thinking, Okay, I know what canine guidance is. It’s about the only thing you learn about occlusion in dental school, right? So canine guidance is when the patient bites together. And as they bite together, and then they bite on the back teeth and they’re about to now move that lower jaw side to side, they’re now grinding or they’re taking an excursion either left to either right. Now, certain teeth contact at certain points as they grind their teeth left and right. And when they’re grinding from in to out, so in their normal bite to out left or right, the teeth that are contacting are the canines. Okay? Now this can transition quickly on to the anteriors. And that’s still canine guidance with a rapid transition to anterior guidance, that’s fine. But if they start in canines, but now they’re involving premolars and molars, or that is now called group functions, that’s the difference between canine guidance and group function. In canine guidance, you’re pretty much only on the canine, and then you maybe come on some anterior teeth, whereas in group function, you may still be on the canine but you’re also on some pre molars or sometimes like an anterior open bite situation, you may be on just the molars and not the canines and not the premolar, that still group function. Now, what is the relevance of this in terms of Protrusive Dental pearl? Well, sometimes when you are observing for canine guidance, or when you’re observing a patient’s occluding scheme, you’re checking their lateral excursions, ie when they’re going side to side. And you may notice that as you tell Mrs. Smith to grind left and right, it looks as though that she’s in canine guidance. But okay, when you actually get Mrs. Smith to clench really hard together, and then grind left and right, you might then notice that actually, this patient is not in canine guidance after all, this patient is in group function, okay? And the first person to teach me this was Pav Khaira, who is the host of the dental implant podcast, and he also came on episode 76, to about finding your niche in density. So if you haven’t listened to that, please do listen to that. Now he taught me this concept He showed photos of himself, like in canine guidance, and then pressing really hard and actually, he was in group function at that really blew my mind that, like how come they never, This is important. How come they never taught me this in dental school? Because when you complete someone’s restorations, and you think that you finished these restorations in canine guidance, but really if you check a bit more thoroughly, you know, is that actually they’re in group function. Is that a really a bad thing? Well, depends if you designed for all your restorations in that specific scenario to be in canine guidance but really, they’re not, then that is kind of a problem, right? It’s not what you plan to achieve. It wasn’t as part of your goal. Now when I had Andy Toy on the episode, now, if you wanna go back some episodes, it called the posterior guided occlusion episodes, part one and part two. Andy Toy took this a step further, he explains that actually, it might be more than just we’re not in canine guidance, we actually had these non working side guidances. Now I don’t like that term, non working side interference, because interference is like a nasty word. It’s like it’s in the way, right. So just to roll this rewind, back to basics. What I mean by a non working side interference is if I’m grinding my lower jaw to the right, okay? I should be feeling contacts on the right, that’s fine. That’s working side. But if I’m grinding to the right, and I’m feeling okay, I’m feeling that my left teeth are dragging or touching or grinding. Some people will classify that as a non working side interference. I like to call that a non working side guidance because interference, very harsh term, but actually, even those patients who you think are in beautiful canine guidance, and you see the opposite side completely disclude that you see a big gap between them. When you get the patient to grind together really hard to the other side, they might actually have some areas where they have a non working side guidance. Okay, so let’s just play you a snippet from this episode.

[Andy]
Right? So you’ve got group function with posterior disclusion on the proposed opposite side. Yeah? Okay. Now just slide out to preferred side again, about a third of the way out. And this time, you’re going to crunch back with force. Okay? And just in feel what’s happening on that opposite side, as you come back in to MIP.

Main Podcast:

[Jaz]
So ultimately, what we can learn from Pav Khaira and what we can learn from Andy Toy, is that when you’re checking the guidance, don’t just check it like in a passive glinding state, check it with force, okay? Because you have to ask yourself, when is this patient going to generate force? Okay, well, they’ll generate a joint function when they’re chewing something hard when they’re really going for it, technically has some force being generated. But think about a function is that there aren’t that many tooth to tooth contacts happening during function actually, there’s food in the way, right? There’s a bit of chicken in the way of something, right? There’s a you’ve got a bolus that you’re squeezing together with your teeth, and therefore your teeth don’t touch very much. So really, the main issue or the main consideration here is parafunction. When our teeth are grinding during the day or at nighttime, and they’re rubbing together in an inside to out motion, whereas an outside to in motion is functional. Inside to Out is a parafunctional, it’s grinding, okay? It’s something that really shouldn’t be happening, but it does is very common, okay? Therefore, I want you to check it because when you place someone’s restorations, I want you to check it at the time where it’s going to be tested, ie in parafunction, your restorations, your materials that you place are going to be tested by the patient, they’re gonna be under cyclic fatigue. And they can be under the most fatigue during parafunction. So it’s important, you recreate that environment in the chair. So you can dictate where you want the contacts to be. If you’re happy with everything, do you need to make something steeper? Do you need to make something thicker? wherever it might be?

So I’ve been speaking a few minutes, and I’ve introduced a few concepts for you, right? And these concepts, they’re very, very difficult to find evidence for, in fact, the quality of evidence in the whole rounds of occlusion and TMD is really, really poor. Okay? And basically, most of what you read and even most of like the textbooks on occlusion that you read, when you go to the references section, it’s mostly theories, concepts, observations, suggestions, even the titles of these papers are suggestions or observations, okay? A lot of the evidence in occlusion is about articulator accuracy. Now we know an articulator is not the human, okay? We know it’s trying to mimic the jaw, but it just can’t, it will never be able to mimic the jaw because the jaw is biological, there’s squishy parts, there’s PDL, and therefore, that’s where the shortcomings are of articulator. So all this evidence base, you read on how to make your articulators programmed a certain way, essentially, they’re going to help you with your patient while your patients in the chair and a lot of the other papers are looking at like proprioception from teeth, muscle behavior, for example, an anterior guidance, we know that our muscles don’t contract as much compared to when they’re grinding on their back teeth. So we know that already, but we’re not able to draw any conclusions from that. And even a lot of the papers are all about reproducibility of centric relation, and don’t worry if you’re thinking, whoa, whoa, whoa, whoa, I’ve skipped the hair down. I’m talking about centric relation now. I’m gonna come on to that nicely, but just know the fact that there’s really a lack of evidence and lack of quality evidence, even when it comes to, you know, do certain malocclusions cause temporomandibular disorders, right? Because the classic people like Luther 2010 Cochrane Review says there’s a real lack of evidence to support that malocclusions can contribute to TMD. Now, that doesn’t mean that it doesn’t cause TMD. It just means that there’s a lack of evidence. So is there really factor in and sometimes I value people who’ve been practicing for 20, 30 years, and they’ve made some valid observations, because remember 1/3 of evidence based dentistry is the clinician’s experience as the same with bruxism and TMD. We know that lots of patients grind their teeth and some of them grind really hard. Yet, these patients may not get TMD, whereas a lot of patients who have TMD, they don’t have major signs of bruxism. So it’s one that we can’t prove, although papers go for and against. So generally, the general theme is that occlusion has poor evidence base, and so does TMD. Why is this? Well, try to understand why, let’s compare it to a completely different field of study.

Let’s talk about the science of bonding or biomimetic dentistry trying to recreate highest bond strength, try trying to make sure our composites and our ceramics stick to tooth as best as possible. Now, if you’re designing some studies, to find out how well your restoration stick, or how well your restorations perform, we know that we can follow clinical protocols that from one patient to the next patient, you can keep pretty much consistent. We know that we can get large samples because the restorations that we place and we can follow these patients up. And also some of these studies which are done in the lab IE benchtop studies, they still help us because even if you have an extracted tooth, and you’re etching the enamel and you’re bonding and you’re checking the bond strength, a lot of that information can be transferred to in the mouth bond strengths, right? Although Yes, we know when a tooth is out is not as moist, or whatever is dried, is brittle, all those factors. But a lot of these studies when they quote Hey, this bond to normal, it’s gonna give you this when you megapascals that’s probably been done on a lab based study. So when it comes to the science of bonding, because it involves material science, and tooth structure, a lot of this we can do outside the mouth, right? Now compare this to difficulty in occlusion and TMD evidence, right? There are just too many variables. Okay? Let me make it really tangible for you. Imagine you have to design a study, and you’re looking at canine guided rehabilitations versus functional occlusion. Now, what I mean by functional occlusion is when Riaz Yar came in podcast some episodes ago, he talks about how over the years he used to be a disciple or a preacher of canine guidance and he really moved away from that, he’s really moved more towards group function. He thinks that the really key determinants of good occlusion are the first molars and the upper incisors, right? So if we can put like, those are completely two different schemes, right? One is like pretty much more group function based and one is canine guided occlusion. So if you’re going to rehabilitate someone, right? You’re going to give them like, you know, 32 crowns or lots of restorations and change the occlusal vertical dimension right? Change their bite, basically. And then you’re gonna give them either canine guidance or functional occlusion and you’re gonna check Okay, which is the best occlusion, right? Well bear this in mind, right? Lab studies are gonna be pointless, right? Doing it all in an articulator in group function and articulator in canine guidance and trying to come up with some sort of conclusions. It’s gonna be pointless. Okay? So we know that that we can’t correlate lab based studies when it comes to testing occlusal schemes to our patients, and we have our patients, the biggest problem we have is that populations are just too different. For example, people come in different sizes, people come in different skeletal classes, right? How are you gonna make someone who’s severely skeletal class three into canine guidance? Okay? It’s not going to happen. Okay? Same with someone who’s very close two, Okay? They’ve got a huge overjet. Okay, how are you going to make them class one. How you going to make them have canine guidance? Yeah, it’s possible. But then you have to bear in mind that’s different to someone else who’s less class two. And that’s very easy to give them canine guidance. So those are some of the stumbling blocks. Now age of a patient, okay? A young patient we know is different to an older patient. Now, an older patient might have more restorations and may not have as good of a healing capacity as a younger patient. The sex between a male and a female, obviously, now, male, female, different populations. Right? Now, when it comes to bonding restorations for males and females, you know, you’re probably not going to have any difference, right? The enamel, dentine is probably gonna be the same, if not very, very, very similar. Whereas when it comes to male versus female, we know that TMD will affect women compared to men by a ratio of 9:1, so nine times more women will get TMD compared to men. So isn’t that going to have some sort of bearing on our findings? Now, what about people with a long face versus a short face? Right? Their biomechanics is gonna be different. And what about their muscular hypertrophy? What about that lady with very thin muscles, compared to that patient, when they clench together, you feel this massive bulge. Okay? That second patient is generating a lot more force. So how will that affect your findings when you’re comparing these populations? And what about the periodontal status, we know that the periodontal states can vary in different patients at different times in their life, and you might have someone with a reduced periodontium, ie that they’ve already lost some bone in the past. So they might have a little bit of mobility compared to someone else who’s got zero bone loss. And, in fact, they’ve got really thick bone, they’ve got exostoses, those patients are gonna be very different. Now compound that with the different angles and cuspal slopes that patients have, so people naturally have steeper cusps, and people have shallow cusps. How will that feed in to your findings? And what about the big one? Do they bruxs? Do they not? How many minutes a night do they brux for, for example, some landmark studies show that the average normal bruxist so someone who doesn’t grind very much, just grinds for about two or three minutes a night. Okay? So that might be me and you, for example, well actually, it’s definitely not me I’m actually a massive grinder, right? So I’m probably someone who’s called a pathobruxist. So I’m probably grinding for more than 11 minutes per night. With significantly sustained muscle contractions, I’m grinding with much more force. So patients who will grind to varying degrees, they’re different, right? So how are you going to test these when it comes to the different occlusal schemes? And then of course, you got heavily restored versus minimally restored, tooth contact time. And you know, what the list is just completely endless, for example, this is just imagine you’ve somehow found the perfect two population samples that you’ve counted for all the confounding factors, you’ve got two huge populations that represent the general public really well. Okay. And then you have to ask the question, does occlusion change? Of course it does. We know that teeth wear we knew that, we know that patients diets are different. And we know that all of those factors I mentioned above, right, can change. I mean, heck, patients could even change their sex, right? So you know that their muscle size can change, you know, that they’re gonna get older. You know that they’re gonna grind more, grind less, enter periods of stress throughout their life. So how can you actually study these two populations or study these two occlusal schemes? On functioning humans? It’s just impossible. That’s why we might never ever get the evidence we need. And this is why we have so many different occlusal camps or occlusal religions. You know, we’ve got the Dawson, Kois, Pankey, Neuromuscular, PGOs, Spear, just to name a few, right? So each one of these camps think that maybe they have got it understood the best and the occlusal schemes or the slight nuances. I think, personally from studying a lot of these guys, is that they’re all doing the same thing really, they’re trying to improve the health of a patient. They’re trying to get longevity of their restorations, but they just have a few different theories. And this actually is a source of a lot of views, or fistfights, sometimes at US congresses I hear so they have slightly different views. But the way I see it is what can I learn from each camp, okay? Because that’s why I’ve done some Dawson, that I’ve done some Spear. And I’ve listened to Lukas Lassmann, who is a disciple of Kois and Michael Melkers, who and my principal, Hap Gill who’s talking about Pankey. So I have got lots of mentors from different schools of thought. And I just like to learn from all of them. Because I think there’s so much to learn. If I can just get a little bit from each school of thought then I can come up with my own school of thought, and I pretty much have and you will, too, you will have your own philosophy. Now, some episodes ago, I recorded about protocols and philosophies. I think it was one of the first ever interference cast that I did. And I talked about Dr. Jerry Lim in Singapore who inspired me. And I asked him like, hey, Jerry, which occlusal camp should I train with? Right? I don’t know which one to go with. They all seem so good. And he said, you know, why it doesn’t matter, just pick one, and go all in, like really learn it to a tee. And you will find success. And I think that’s true. Because all of these camps, right? They might treat someone differently, the end result might be slightly different. But they all seem to work and they all enjoy success. Now I like taking Kois, for example, I’d like one of his quotes, which is “The idea that we do have controversy makes us realize that we really do not have solid evidence based science to help us make decisions.” So I appreciate the fact that Kois being such a huge educator in Seattle understands that actually, we really, as a profession, lack evidence, and therefore that’s why we have so much controversy, I still respect everything Kois has to teach. In fact, what an amazing Dentist he is and so many of his publications that I read, I’m just in awe of him. So we should learn from people like Kois. And we also have excellent clinicians, like Ed McLaren, who said, “It’s very difficult to say that one occlusion is perfectly correct for all individuals. And I don’t think we’ve identified an ideal occlusion for a specific person.” If only it was that easy. So for example, you might be a dental student right now. And you’re learning all these things at dental school about the perfect occlusion, canine guidance, the mutually protected occlusion, everything in balance, that kind of stuff nice and smooth. But you see your first patient on clinic, and maybe they have an anterior open bite, or maybe when they bite together, there are complete skeletal class three, right? And you’re like, Wait, hang on, this doesn’t look like the textbook at all. And when you see that in practice, and you see a year on year on year, and you start seeing that, okay, a lot of patients have, let’s call it sub optimal occlusions, or non textbook occlusions. And they’re doing just fine. And it makes you think there’s got to be something else at play, you know, there’s not just the occlusion here, there’s a whole person behind it. There’s a whole masticatory system at play here. So we see these things in practice, which aren’t quite like what’s in the textbook, and then you start to go to occlusion courses. But then you realize that since this term center relation was created, it’s changed definitions 26 times as a profession, we can’t even agree on the term centric relation yet is supposed to be this really big deal and occlusion, which I’m going to explain now. Right?

So let’s talk centric relation. Okay. It’s a very controversial topic. A lot of scientists think that there’s some sort of magical place that you put some in centric relation, and they will stop bruxing. This is not true at all. Okay? You put someone in centric relation, and suddenly, this might get rid of their headaches, or this will make them a more complete person or whatever, you read a lot about the value and importance of centric relation. Some dentists really overplay this, right? Let’s look at the definition. Let’s talk about why I think centric relation has a role. But it’s not this amazing thing that everyone needs to be in centric relation, because remember that 97% of us are not in centric relation. So we are normal. So essentially, the people who are IN centric relation who are abnormal, so let’s stop chasing this perfect ideal thing. Now we know that there is a benefit of centric relation. I’m gonna come to that in a moment. Let’s just take a look at a glossary of prosthodontic terms definition from the latest one in 2017. Okay, so don’t write this down. Don’t make a note of it, please. Okay? Because I’m going to explain why shortly. But you definitely don’t need to make a note of this, okay? It’s a maxillomandibular relationship, okay, independent of tooth contacts. So we know that you can actually grab someone’s mandible, put them in centric relation and stop hinging, but we know that as long as a tooth doesn’t touch that centric relation, as long as soon as the tooth touches, technically, you’re not in central relation anymore. And now you’re in a tooth born position, which might have a different name like centric relation contact point, for example, but to be in purely centric relation, like your complete denture patients, right? You take the dentures out, you can put them in centric relation. So it’s not a position that’s dependent on your teeth right? In this position independent topth contact, in which the condyles articulate in the anterior superior position against a posterior slopes of the articular eminence, this is a bit which confuses a lot of people or loses a lot of people that everyone can follow the fact that it’s between the mandible and maxilla, everyone can follow the fact that there’s no tooth contact, but it’s this anatomical reference that confuses people. Okay. Why does it confuse people? Okay, I think there’s a very good reason why it confuse people. Because when you’re in the clinic, you’re trying to apply centric relation, right? You can’t see the condyle, you can’t see the articular eminence, you can’t see the posterior slope of the articular eminence, right? So this is a bit where people get confuse because they can’t see it. It’s just this abstract concept of what might be happening in the jaw unless you get a scalpel and actually dissect and have a look at what’s happening. We don’t know this, right? So this is where the term I know is needed. But unless you can see what’s happening, which you can’t, it’s not going to help us right? Now, it’s in this position, the mandible is restricted to a purely rotary movement. Now I’m going to play devil’s advocate and say that this is probably not true. Okay. Some of the CBCT data, MRI data showing that actually, there’s no such thing as pure rotation. There’s always a little bit of translation, but let’s just go with it. Okay, let’s just go with the fact that it’s pure rotation, I think that’s usually to benefit the articulator more than to benefit us, right? So, that is confusing, right? If you’re listening to this, you’re driving like, Whoa, okay, now, this is really confusing. This is why I don’t want to learn occlusion anymore kind of thing. I think, you know, let’s look at centric relation, not in terms of this very long paragraph, which by the way, a lot of dentists are upset about because they feel as though there was no mention of the disc, right? So we know that between the condyle and the articular eminence, there should be a disk, right? So to really be in centric relation, right? There should be a disk on top of the condyle, right? And a lot of people are upset that in this latest 2017 Glossary of Prosthodontic terms, there was no mention of a healthy condyle-disc relationship, okay. But anyway, going away or moving away from that description. My take on centric relation, that is that the anatomical description is not really clinically relevant, like I said, right? For me, as long as it is repeatable and reproducible. Now, there’s also different ways to check and we talked about that another time. But as long as you’re in the same place, every time be on your splint be on your restoration, be in sometimes just the way it feels like you can, you know, you can deprogram them straight away. whereas others, they are really stiff, you can’t move their jaw, right. And they’re the ones who need what we call deprogramming, allowing their lateral pterygoid muscles to forget where their bite is, allowing it to relax, allowing the lateral pterygoid muscle which is pulling on the condyle, to just let go, let that muscle stretch, and to let it go in that anterior superior position where it wants to be, right? But for us, it’s the most important. The most important takeaway thing about centric relation is that is a convenience position, right? Like, if you’re restoring someone, and you decided that okay, you know, open up their bite. And now you’re going to fill in with lots of crowns and lots of fillings. You shouldn’t just pick but you can do, but you shouldn’t just pick a random position, okay, let’s just build your bite forward by two millimeters and just build it there. The patient might adapt, but they might not okay, but then what if halfway through, you’re trying to move between temporaries and then definitives. And then you just hacking away and you’re just observing where the jaw is ending up and just finishing in a random place, there’s a real danger that you lose what you made in the diagnostic wax up. And when you’re transferring that to the mouth, everything just gets lost. But if you go to this clinically repeatable position, which is basically not quite the furthest back, you can go so this whole term of retruted contact position, very old term were going to move away from that, that’s like pretty much shoving the condyles back as far as they want to go, right? We don’t want to do anything to do with that. But this position when you are there, and it is repeatable, that’s a very useful position for us, okay, so that when we do take off our temporaries, and we do place our definitives, then we’re trying to then balance our restorations. And our end goal is always that same position that we had from the beginning and not this random position, you can always be sure that what you’re trying to achieve on the articulator we’re trying to achieve from the blueprint is going to end up like in the mouth with the correct guidance as you planned it. If you’re going to random arbitrary position, you might end up where you want to go, where you might just get random contacts that you weren’t expecting. So that’s the major benefit for me of centric relation, okay? And it has to be this sort of this snug position. I like this snug term, like centric relation is snug, right? And when you’re manipulating the mandible, the lower jaw and you’re moving around and you’re in this hinge in motion. It’s called Romancing the mandible. And there is something quite special about when your patient centric relation just hindering them away. And with experience, you gain that so if you’ve never done this to a patient before you will gain that experience with time and we have to remember that actually centric relation, most of our dentistry is not going to be in centric relation, okay? Most of our dentistry is going to be in whichever bite they already have in their existing maximum intecuspation position, ie how their teeth habitually bite together. This only I trying to get them more fancy, we’re trying to open up the bite, we’re trying to change things in significantly, then that’s when we’re entering centric relation dentistry. And for you as a restorative dentist, it is a point of convenience.

Now to confuse you even further or even less, I hope after this little segment is centric occlusion, right? Okay. This is a massive source of confusion. And this really pissed me off okay, Excuse my French but let me tell you why centric occlusion pisses me off. Okay? Right now, whatever you’re doing before you advance, just in your mind, think what is the definition of centric occlusion for you? Okay, in your mind, what did dental school teach you is centric occlusion? Okay, so you’ve got your definition in your head. Okay. Let me tell you what the glossary of Prosthodontic term said in May 2017. Now May 2017, okay? The 9th edition of the glossary Prosrhodontic terms came out and the top song in May 2017 was despacito. I will not sing it for you Don’t worry, okay. And it define centric occlusion as the occlusion of opposing teeth, ie the upper teeth, when the mandible is in centric relation, okay? Let me say that again. The occlusion when the mandible is in centric relation, okay, this may or may not coincide with the maximum intercuspal position. So, for all of you who said that is the same as MIP? or is your habitual bite? Or is where all the teeth meet together when you bite? You are wrong, right? So, dental school taught me that they taught me that centric occlusion is MIP. But actually, the glossary says that no, in 2017, it said that it’s your basically is your centric relation contact point. That’s a term I like. The reason I like that term more than centric occlusion is because lots of dentists will say centric occlusion. And they mean completely different things. This is absolutely catastrophic for us as dentists who want to learn, who want to advance in the field of occlusion, because you might communicate with a dentist, or you might read a book, or you might watch a webinar. And you get so confused by which definition of centric occlusion they’re using, because a lot of dentists I know, are still using the old definition of centric occlusion, which is MIP. Now let’s go back in time, okay, let’s go to December 1987, the fifth edition of the glossary of Prosthodontic terms, okay, the number one song that year, that month was faith by George Michael, another cracker. And actually, the definition was the same as it is in 2017. So here I was thinking at one point that oh my goodness, I can’t believe I didn’t realize in 2017, they changed it, well actually no. Even in 1987, it was the exact same definition. Okay, can you believe that? Right? So I am a little bit annoyed that when I started school, in 2008, okay, in Sheffield in dental school, they taught me that it’s MIP. Why didn’t they teach me? Why my tutors teach me that was a 1987 definition at least. Okay? So I’m thinking that Whoa, a lot of people are just stuck in some sort of like 1956 description or something, right? Because when you go back in time, even more to July 1977. The top song was undercover Angel. Okay? A song I hadn’t heard before it actually YouTube it when I was searching this up, okay? And that’s where they described centric occlusion as the centered contact position of the occlusal surfaces of the mandibular teeth against the occlusal surfaces of the maxillary teeth. Man, I don’t even know what that means. That’s so confusing. Okay, but I guess at least from 1987, we can safely say that the definition is not MIP. Okay? It’s the first point of contact as your teeth are in centric relation, the first thing that hits so I always use centric relation contact point, the first place where you hit so no wonder we are confused in occlusion. Not only did centric relation change 26 times, we are still confused this day as a profession about the definition of centric occlusion. Okay, why does this matter? Like what you’re saying, Jaz? Come on, man. It’s just definitions. Calm down. It’s not going to affect the beautiful dentistry that I’m gonna give my patient. Well, it does matter, okay? And even as far back as 1956 in the Journal of Prosthodontic dentistry, where in that year, the very first Glossary of Prosthodontic terms was released. Okay, Carl Boucher said “The correct choice of words to express an idea is important to an author, because the communication of his idea is his objective.” The dentist and the student are the readers of the chosen words. The words must have the same meaning to them, as they do to the author, the need for a precise system of the nomenclature with precise definitions for terms use in prosthodontics is obvious. And I totally agree. Only can we start merging these religions and start playing mice, we actually have a level playing field of terms. So hopefully now, after this little ramble, you know that centric occlusion, according to the latest terms, is the first point of contact, it’s not MIP. Why don’t we just use maximum intercuspation position as the term for MIP and move away from CO.

Now let’s look at the most important definition I haven’t covered yet. Right? Like what is the definition of occlusion? Like why even study occlusion? I’m not talking about the very long and boring definition in the glossary of Prosthodontic terms. I’m going to give you a couple of definitions of occlusion I really like. These two definitions of occlusion I’m going to share with you helped me massively to understand what we’re trying to achieve with occlusion, what is occlusion in daily practice? Okay? So first one is from my mentor, good buddy, Michael Melkers. He said, “why don’t we just rename occlusion to stopping your dentistry from breaking?” Okay? It’s basically a solution to help meet a goal. And that goal is to get longevity and good looking teeth where you want them, right? So if you start thinking about occlusion like that, and not when the teeth come together, and as you go into excursions and this kind of stuff, right? It’s just about getting predictability and stopping your things from breaking. And in a similar fashion, Ed McLaren, who also is we have at the Tubules Congress in Brighton. So I look forward to seeing him again, great clinician, UCLA, he says that “Clinician’s are trying to design the way the teeth come together, so that we prevent some sort of breakdown, whether it’s of the teeth, the periodontium, or the joints.” okay? I love the term he uses, which is called force management, right? Occlusion is basically force management. So when you think about occlusion as force management, you start to think of it perhaps a little bit too biomechanically, rather than deserved as a human with emotions at the end of the body. But I do like this concept of force management. Okay? A lot. I think when you’re rebuilding, complex dentistry, force management should be was all about. But I’m going to completely play devil’s advocate here because you need to hear this. Okay. So far, we talked a little about, you know, canine guidance, some different definitions of centric relation and centric occlusion, and what actually occlusion is to me and why it’s important to prevent failure. But is occlusion really to blame? Right? Like, you know, how people say, ‘Oh, this patient had a really bad occlusion Or it’s because of the occlusion, this patient got TMD or check the occlusion there might be something wrong. What you have to think, right? How many minutes a day do our teeth touch together? How many minutes a day? Should they touch together? Right? And if you’re thinking 20 minutes, you’re right, right? So if our teeth should only touch 18-20 minutes a day, then why are we so obsessed about 1.4% of the day? Okay. We don’t focus on the whole 98.6% a day. No, we have a whole religions and courses and everything based around occlusion, which apparently, most of us should only be doing for a tiny fraction of the day. Okay. So why do we place so much emphasis on this small portion of the day, right. Now, granted, some people will be clenching, grinding during the day and at nighttime, and they will probably exceed that 18 minutes. And this patient might be the same patient who develops muscular hypertrophy. Like if you think about it, this patient is going to the dental gym, this patient is working out their masseters, temporalis, middle pterygoid, right? And therefore, they might have larger muscles. Now the problem with larger muscles is they start generating more force. So maybe we start seeing a little pattern here.

Now to make it, to drive it really home and make it tangible. I discussed this with my one of my mentors, Barry Glassman who really got me to think about not occlusion, but occluding right? let that sink in. Not occlusion. But occluding Let me explain this concept to you, right? One way that Barry explained it is when you open up an anatomy textbook, and you’re looking at the anatomy of the entire body and you see a skeleton laying down, okay? what kind of posture or what kind of position is that skeleton in? Well, it’s completely like you know, like completely flatted right the skeleton is laying down there’s no bones in any different funny positions that just the arms are by the side everything is like normal. What you don’t see in anatomy textbook is a skeleton I can opposing trying to sort of bold pretend biceps, right? You don’t see the skeleton in a contracted way. Why? Because you need muscles for a skeleton to be able to move its bones right? Now, when you’re looking at bones. You’re just seeing bones, there’s no muscle. So why is it that in dental textbooks and in all the photos that we see, we see patients in their maximum intercuspal position, all the textbooks anatomy, dental anatomy, occlusion courses. Oh, let’s finish. Let’s look at the post op image right? The patient’s teeth together. Why are we doing this, right? It’s the same as seen that skeleton in that textbook with the biceps bulging right? The point I was trying to make is that a we need to think that actually is not the bite that’s to blame when things go wrong. It’s the biting IE is the muscles, right? It’s the muscles that contract that bring our teeth together. So sometimes we put too much emphasis on the bite, and not enough emphasis on the biting. And if you think about it, those patients who are biting for longer with higher forces with stronger muscles, they might be the ones that could cause more issues, more damage, more breakdown to the PDL, more breakdown of the periodontium, more breakdown of the joints, and more breakdown of the teeth. So remember that, yes, occlusion is importan but occluding might be the missing link between why some people get problems and why some people don’t. So how do I bring this all together from going to so many different occlusion courses and learning how to wax up these teeth and spending so much time to make sure that our fine tuned a patient’s occlusion versus, actually it might not be so important because it’s the OCCLUDING that’s important, the muscles, ie the role of splint therapy, or the role of counseling your patient for awake bruxism might be more important, like we know, for example, some patients when we finished our restorations, and we get them to bite together, right? Some of them if they bite together, and you’ll notice that Whoa, you’ve jack them up open so much, right? And there’s like, no, there’s so much space on the other side that things aren’t touching together, the MIP is a way off, okay? You’ve left them really high or really proud. But when you ask the patient how things feeling, they say it feels great. Whereas you go the other patient, everything looks like you’ve got, you nailed it, right, you’ve nailed the MIP, you have got everything looking perfectly. There doesn’t seem to be any high spots, but the patient will tell you, yeah, I can feel that this is a tiny bit high. I bet that second patient is probably someone who’s used to feeling how their teeth meet together, they’re so used to it, that they’re spending a lot of time in that position, hence why they’re able to give you that really high level feedback. So the answer might be treating your patients in terms of risk. That patient who does feel every little micron, that Princess and the Pea patient, that Goldilocks patient, okay? When you engineer that patient, you know that you need to over engineer that you need to really fine tune the occlusion. And if you’re giving that patient a rehab, and they’ve destroyed their teeth before, you’re going to follow the principles of a minimally stressed occlusion, you’re going to try and get everything contacting the same time, you’re going to try and get anterior guidance, canine guidance with the transition to anterior guidance, which I’m going to probably cover in the next episode, because there’s only so long I can cover in this one. But what I’m trying to say is you’re going to really work hard to make sure that you design that occlusion, you design that blueprint, you take full control of what you’re trying to do. Whereas that patient who has very soft and gentle muscles, who is probably an 18 minute chewer, or maybe even less, and who really, if you leave them proud and jacked up, they won’t even realize that patient when you’re restoring them, you can get away with a lot. You don’t have to give them that textbook occlusion, right? You probably still will, because you want to reduce your risk, okay, you have a pain patient. You want to follow the textbook rules to get maximum success. But sometimes you can get away with a lot more with this patient. That’s how I like to think about it. I’m going to echo again Ed McLaren’s sentiments about force management when you start getting patients to bite together instead of looking at them as dots and lines you think of force management you start taking a step back, you start feeling their muscles, you start feeling their joints, you start knowing that okay this patient’s grinding and when they’re grinding they’re generating a lot of force because there’s a lot of resistance to movement right? They’re struggling to move their jaw and they’re struggling to move their jaw, guess what’s absorbing all that force? It’s the teeth, it’s the PDL whereas someone else as they’re grinding they’re gliding beautifully left and right that patient may not be generating as much force. So it’s all about force management, it’s about being a good conformer. Why mess up someone’s occlusion? Why change their occlusion if everything is working for them?

So most of our daily bread and butter Dentistry, right? Become a good conformer, check the occlusion thoroughly with your fingers. When you put your fingers, your fingertips on the teeth and you get the patient to bite together you can sort of figure out what kind of occlusal contacts they’re gaining. Some will feel heavy, some will not feel not so much and then at the end you’re hoping that once you’re done with the restorations, when you’re done with your crown or when you’re done with your composites that things will feel the same with your fingers again or you and even when you put your articulating paper in the marks will look the same as they did before. Now I found it very useful to take an intra-oral camera photo pre-operative contacts and compare that to post-operative contacts so I know that I have conformed to the patient’s occlusion i.e I haven’t changed anything, okay? It’s a bit like why would you want to change anything, right? It’s a bit like when you’re five years old and you go into the kitchen and you know where the secret chocolate stash is and you you’re kind of you know sneaking around like a ninja and you find that chocolate, right? Once you’ve eaten that chocolate, what do you do? You hide all the evidence, you try and put everything together back how it was so no one realizes you are there.

You want to be that dentist, okay? You want to go inside okay and you want to come inside you want to stop your restorative procedure coming away and you’ve hardly changed the thing, the tmj, the periodontium the dentition hasn’t had to do any or very little adaptation, right? Be that dentist, who is that five-year-old who puts everything back together how he found it and lastly one big lesson i want to just give you now to give you some sort of a food for thought for future lectures is test driving your changes, right? Sometimes when we’re doing bigger cases and we’re going for lots of crowns and we’re doing extensive restorations it is so so so important to test drive everything because that’s when you can test whether your force management is correct, that’s you can test where the patient is comfortable, that’s when you can check that the patient is as you planned them in centric relation if you plan them in centric relation it’s not always that we want to go into central relation and i can cover that in the next episode a bit more but in a nutshell, there are times where you don’t want to put someone in centric relation because imagine when you put someone in centric relation their lower jaw goes all the way back okay? What is that doing to their facial profile right? That’s probably not making them look very well also what is that doing to their airway, okay? That could be collapsing their airway, right? So there are times where you would actually make a conscious decision not to rehabilitate someone or restore someone to centric relation because that position may be less favorable for other reasons, aesthetic or airway to give you two examples.

So I hope I haven’t confused you and I hope that gives you some sort of food for thought about hey why are we so bogged down in occlusion where actually a lot of our patients are only chewing for 18 minutes a day, well actually some patients might be doing more than that be more destructive, generate more destructive forces and in that patient you might be over engineering them. You’re probably safer off really looking into force management whereas someone else you can just do the best job you can to conform and that’s all you need to do. Now maybe next time, next episode we can look at being a good conformer. What i mean by that is what kind of context are you looking to finish with right like there’s a whole theory of tripodized contacts to make sure that everything is nice and stable is that really necessary? We can look at what we check for in an occlusal examination. The relevance of the centric relation contact point. Now we talked about centric relation when the teeth meet together finally in centric relation, what is significant about that, okay? Both in terms of your planning and also in terms of your daily patients that you see, are their teeth at any risk by being in that position and i also want to just introduce you to these terms which are freedom from centric or some people call it freedom in centric and i’ll tell you the nuances between them but i think that’s really good because when i’m finishing an orthotic case, I want them to have this wiggle room and i’ll tell you what i mean by freedom from centric and why it might be advantageous to have your patients in this, have this feature in their occlusal scheme and I’ll touch more into what if you do restore someone not in centric relation, what are the bad things that can happen so for example if someone is going to have a messed up aesthetic result or you’re going to mess up their airway and you’re going to choose not to put them in centric relation or you’re just going to do a rehabilitation and you’re just going to be lazy, you’re just going to open everything up and stick some restorations on and hope for the best what potential considerations should you keep in mind if you’re doing that because i know some dentists do that and that’s fine but there are some things that we should know, some compromises that you might be making, some risks that you might be taking.

Jaz’s Outro: So thank you so much for listening or watching all the way to the end. I really appreciate it. Now if you are wanting to learn a bit more then the next video i have for you to watch if you’re watching on youtube is or if you’re going to protrusive website I’ll link this video on. I’ve got a video on the nine point checklist to make sure you never have a high restoration again so that when you’re doing your composites on the rubber dam when we take the rubber dam off you get the patient to bite together you’re not having to hack away so much or hardly anything. So my best nine tips so you can click here now if you’re watching on youtube or if you go to protrusive.co.uk i’ll link that short little video i think it’s about eight minutes on just my top tips on making sure that when you do conform it’s less stressful for you. Thanks so much for listening all the way to the end. Don’t hold your breath for part two because these episodes take me a long time to come together. Do check out the newsletter for these kind of updates if you haven’t already is on protrusive.co.uk/newsletter and i’ll catch you in the next episode.