Should our Restorations Follow Textbook Anatomy? Tooth Morphology – PS005

Protrusive Dental Podcast

When restoring molars, should we ALWAYS try to recreate textbook anatomy? (spoiler: NO WAY!)

What preventive measures can we use for toothwear?

Tooth Morphology in the Real world!

In this episode, Emma Hutchison and I explored the nuances of practical tooth morphology. Textbooks provide us with idealized versions of dental structures, but how do these perfect images translate into real-life practice? Can and should we aim to replicate these diagrams exactly in our dental work?

https://youtu.be/OcdQRTV7jpY

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Need to Read it? Check out the Full Episode Transcript below!

Highlights of this episode:

• 1:38 Introducing Emma Hutchison
• 01:53 First Denture Experience – What is an Overdenture?
• 03:13 The Importance of Complete Dentures in Aesthetic Dentistry
• 8:26 Understanding Tooth Morphology in Practice
• 11:25 Changing the Morphology of the Tooth
• 15:56 Difference Between Morphology of Premolars
• 20:31 Preserving Natural Tooth Morphology
• 27:26 Real-World Application of Tooth Anatomy

Don’t miss the special notes on tooth morphology available exclusively in the Protrusive Guidance app!

This episode is not eligible for CPD/CE points, but never fear, there are hundreds of hours of CPD for Dentists waiting for you on the Protrusive App!

For the full educational experience, our Ultimate Education Plan gives you access to all our courses, webinars, and exclusive monthly content.

If you love this episode, be sure to recap PS004 – Learning Can Be Stressful!

Click below for full episode transcript:

Jaz's Introduction: One of the most common questions I get, and also I used to think of, is when we're doing a composite, let's say you're doing it under rubber dam, posterior composite, are you supposed to make the anatomy look like what that tooth is supposed to look like in a textbook? I. e. are you supposed to basically recreate the textbook in the patient's mouth?

Jaz’s Introduction:
Well, do you know what happens when you do that? Well, this is what happens. The patient bites together and you have to rub it all away. You have to adjust all that hard work away and now it looks like a flat white version of amalgam. So what’s happening there? How can we be smarter? How can we use the textbook as inspiration but also just not end up making all our restorations flat?

It’s a real fundamental and basic question in a way but I think it is so real world. So we are covering today tooth morphology with our protrusive student Emma Hutchison. This is PS005. Remember there’s a series we’re making with Emma throughout the year to cover themes which are relevant to young dentist students and those who are perhaps re engaging back into dentistry.

And also for all dentists who just want to dip into the basics again. I think there’s a real beauty in seeing how far you’ve come and how much you’ve progressed by going through the basics one more time. We were going to talk about orthodontics and stuff but really as a student I thought I wanted to make it more applicable to the real world.

So we deviate more towards tooth morphology and I hope that you can apply some of these tips in practice. Or on the mannequins if you’re still a student. Remember, if you’re a student, you get access to a few secret areas in Protrusive Guidance. All you have to do is send your proof to [e-mail] and of course, download Protrusive Guidance app. And then we will link you up to the right space so you get access to a few special features. Let’s catch the main episode. I’ll catch you in the outro.

Main Episode:
Welcome back everyone to May’s episode. Emma, how is it going? You told me that you just fit your first denture.

[Emma]
Yeah, so last week I had an elderly gentleman and we needed a new lower over denture. So I’ve spent the last however many appointments going through all the processes.

[Jaz]
Emma, for those students who may be a little bit more junior to you, Even though the term over denture might be like a new one and that’s strange actually how it’s your first denture because we at the dental school, it was complete dentures that we did. So tell us what is an over denture and is that standard for you guys to make an over denture as your first denture?

[Emma]
I don’t think it’s pretty standard. So basically my wee patient all of them. He’s so nice. He had incisor two on the lower, which we had I had a previous student that had decoronated and we kept the roots in there to sort of give you a bit more bone support and a bit more just support for the denture and that’s proved to be really good for him.

So you make the denture fit in over these roots and that alveolar bone that you still got a good amount of and that’s just made it so much more stable for him. So it really, really worked, worked in his favor.

[Jaz]
Good. And so this is an acrylic denture, yeah? Acrylic partial denture, and is it just replacing incisors, or are there any molars being replaced as well?

[Emma]
No, so he had no teeth on the bottom apart from those roots from 2 to 2, yeah.

[Jaz]
Oh, so it was almost a lower complete denture except just maintaining the four roots. Okay, understood. Now those roots, are they left exposed or have they got like a GIC on them or copings on them?

[Emma]
They’ve got a bit of GIC on them, yeah.

[Jaz]
Okay, fine. I remember doing this in dental school, we did like a metal coping to give the seal basically and that’s something that can be done as well. Okay, very interesting. You know with complete dentures, a message for students and for you as well, Emma, is If anyone wants to go into the smile kind of stuff, aesthetic dentistry, cosmetic dentistry, call it what you want.

The place to learn it is complete dentures. Because with the teeth and the wax, you can literally set the teeth wherever you want in time and space, right? You can make someone into Bugs Bunny. You can give them a severe overjet. You can give them a deep bite. You just design it how you want. And what you learn from experimenting, okay, what happens when I make my upper and my central sides go higher, further forward, further back? You learn so much about tooth display when they’re smiling. So, great place to start learning cosmetic dentistry is actually with complete dentures. Did you know that?

[Emma]
No, I’d never really thought about it like that, to be fair. No, I haven’t really thought about that, but it makes sense. Yeah, definitely.

[Jaz]
It’s an interesting one. I remember going to a lecture, like one or two years qualified, and someone said the percentage of the population that will be needing, like one of those health surveys, like percentage of population that will be needing complete dentures because they’ll be fully a edentulous will be something like less than 5%.

So the kind of joke he made was, I wouldn’t want to specialize in complete dentures. Yet I see like an increase, thanks to social media and people like Rupert and stuff and young dentists get a lot of satisfaction from doing dentures and complete dentures. I think if you gain those removable prosthetic skills.

Then I think it’s going to make you very employable in the future by any principal, because it’s a huge demand and something that not all dentists are keen on. So it’s great that you got that first one under your belt. What’s the top thing that you learned or a challenge or any reflection that you have in on your experience of delivering this denture?

[Emma]
In terms of going through the process as a student, I would say, you’re making your first denture, you’re not going to be able to do it all yourself. I know for the Bite Ridge, I did next to nothing, really, because the clinician had to be there, basically, walked me through it. But what I would say is, don’t be prepared to go in and do all of it yourself, because you won’t be able to.

But know the reasons behind what they’re doing, if that makes sense. So make sure you’ve watched the lectures and make sure you know what they’re doing, but you don’t necessarily know how to do it just yet, if that makes sense.

[Jaz]
That’s right. You have to observe it a lot of times first before you actually internalize it. And sometimes when you read it on a lecture in a book, when you see it in the real life, it’s a whole different type of learning. And it’s like a disconnect there. And then that part of the brain lights up where it all joins together. That’s a great tip. Don’t beat yourself up that you’ll need someone else to do it for you for the first few times.

As long as you’re making visual notes and actually thinking, okay, I’m going to do this and I’m paying attention and always keep asking why. So I love that you said that. And then something to extend to when you get qualified, and you’re not sure, hmm, what record do I need to send to my lab?

If ever you find yourself in a scenario where you’re like, hmm, what do I need to send to my lab? Always think what information, if the lab get this case, what information would they need to recreate the person, recreate the patient, basically. So, of course, the bite registration is that the lab know where to put the teeth so that when they bite together, there’s not too proud, not too shy. So in your case, what was on this gentleman’s upper teeth? Was he a natural dentition or a denture?

[Emma]
No, he had a full upper acrylic already, which was fine. So we just replaced the lure.

[Jaz]
So essentially you had the lower wax block, the wax rim, and you melted enough of it to the desired vertical dimension, how we figured out. And as long as lots of teeth were touching at once, when you bit together, basically that’s essentially what you went for, I imagine.

[Emma]
Yeah.

[Jaz]
How did you transfer the upper denture to the lab?

[Emma]
So we had taken an alginate impression of that denture. So we sent that to the lab as well. And then once we had the records block on the lower all ready to go, cut some notches in it and used some impression paste got them to fight together so that it could be fit back over to that, the cast of the upper, if that makes sense.

[Jaz]
So yeah, absolutely. So as long as the lab have the upper denture or the upper teeth, basically, and then they can work with that to create the lower teeth. But anyway, we’re digressing. We can always say that for a removable prostho talk in the future, because today’s episode and the notes that you’ll be releasing for May.

Now May for my dentist group on the actual Protrusive Guidance App is orthodontics month. It’s May the force with you. But I feel as though to make orthodontics relevant for students and connecting the real world is, was very, very tricky. And I thought since the first year of the student scholarship, something connected is tooth morphology and like when else will we cover that?

So I think tooth morphology is a great one to cover. You’ve got some great notes for it. So this month we’ll be accessing Emma’s notes on tooth morphology, and so they’ll be able to download them on the usual place on the app, Protrusive Guidance. So go ahead and check it out, and all the other notes that you’ve added, and keep adding them in every month, and you’ll have a nice little library of Emma’s notes, which are absolutely brilliant, by the way, Emma. So, what questions did you have in terms of for me and for Protruserati, in terms of connecting this theme of tooth morphology to the real world.

[Emma]
Yeah. So my first sort of question, it might be a bit vague. So it’s great knowing your tooth morphology and building up for us that are anatomically correct, left, right and center, but how does understanding tooth morphology contribute to you in practice? And diagnosing and the treatment of certain dental conditions as it was putting it all together.

[Jaz]
Do you mean like certain like rarer conditions whereby you know if there’s certain conditions where they get like tulip shaped teeth and that kind of stuff and like certain rare genetic disorders do you mean like that or do you mean like more bread and butter stuff?

[Emma]
Yeah more bread and butter really than anything yeah.

[Jaz]
The first thing that comes to my mind Emma is some people generally have got very bulbous teeth, bulbous molars. And because they have very bulbous molars, underneath those molars, there’s these huge, like, undercut spaces. Right?

[Emma]
Okay.

[Jaz]
That is a real challenge, restoratively. Because when you’re trying to, when they think it caries and you lose a marginal ridge, the matrix bands that we have to recreate that extreme curve can be quite challenging. So sometimes anticipating that, okay, this patient’s got very bulbous teeth and therefore I might need to just slow down a bit and try and recreate my contact here.

And that’s the most common one I’ve seen whereby patients, the kind of matrices that we have, we can’t accept them for what they are. We have to kind of mold them and reshape them to try and fit that exact patient. So that’s the first thing I had. The other one I can think of is a certain population, certain countries, they have anterior teeth whereby they’re really curled up.

What I mean is upper incisors, do you recall that they’ve got three planes? They’ve got that gingival plane, the middle plane, and that incisal plane. Imagine that incisal plane being not really flat but quite curled up. And you might notice this on certain teeth, they kind of curl in. And this can be an issue because If you do a class four composite, so a front to tooth filling, and you’re trying to recreate this on this patient, but then that filling keeps chipping, but actually you realize it’s because it curls in, it’s now in the chewing space.

And that lower front tooth, for example, the opposing tooth is kind of sticky outy. Then there’s a whole mismatch basically, because prostodontically driven teeth. What we’re trying to do with prostodontically driven teeth is try and reduce that failure. And so sometimes you might choose to deviate away from the patient’s more extreme anatomy to make sure that you don’t get that interference in chewing.

So if you imagine if someone’s got this sticky innie tooth and it keeps bumping in while you’re chewing, it’s not going to be ideal. Maybe that’s why some people will chip and wear their teeth away. So those are the first two things I had. I’ll ask that question again so I can think of another example. It’s an interesting one.

[Emma]
Yeah, I was also going to ask you, like, if there was any certain situations where you would change the morphology of the tooth restoratively. Again, maybe quite a vague one, but-

[Jaz]
No, no, I can think of a few scenarios here as well. Okay, so you know that upper incisors have got cingulums, right? Now, this might be a bit more complex to get your head around as a student, but sometimes you’ve got severe wear, you’ve worn a lot of tooth structure away through parafunction, through grinding, through acid erosion, and usually a mix of that, right? So now you’ve got less tooth material. Now, to restore this individual, you need space, you need space to actually put your ceramic, your composite. And so sometimes a technique that we use in restorative dentistry is opening the vertical dimension. Like, like what you do with a denture patient, you open them up, right?

[Emma]
Yeah.

[Jaz]
If you did that on a dentate patient and you open up the bite and then you’re recreating the new shape of the upper incisors for example, if you go with natural anatomy then it’s sometimes very difficult to get coupling of the anteriors.

So what I mean by coupling of the anterior is how do we ensure that lower front tooth, lower incisor, actually touches and contacts the upper tooth, so then you can do the whole anterior guidance and that kind of stuff. So prosthetically, when we’re treating tooth wear, sometimes we may choose to give the patient a bit more pronounced cingulums that are going to be a little bit flat or machined in a way to basically get that lower tooth to hit it basically. Because without this more pronounced cingulum, you’re going to struggle to get the coupling of the front teeth. Does that make sense? Right.

[Emma]
Yeah, yeah, that makes sense. So, that’s one situation where you would deviate from the norm and make that cingulum just that wee bit bigger.

[Jaz]
Absolutely. Because to keep the teeth in occlusion at the front, the downside of that is, and why tooth anatomy matters, is imagine you have a wax up and some tooth wear that you’re treating, and then you do some treatment for a patient, but then the patient comes back and their S sound, they’re struggling, they keep lisping.

For example, lisping is a sign that perhaps you’ve encroached that space because when you make the sss sound, the lower front teeth get into very, very close contact to the upper teeth. Now, some people make S sounds whereby the edges of their teeth come together, so they go edge to edge of their teeth.

Other people, it’s like lower front tooth, lower incisal edge to cingulum. And now, if you’ve done that technique I’ve described, some people will start lisping the S sounds. And so, in that patient, you put the articulating paper in, you get them to count, 60, 61, 62, 63. And you see that mark, and you kind of just adjust it away, and you give them some time to re adapt.

[Emma]
Okay.

[Jaz]
And so that’s why, one time in that, actually, the tooth morphology which you may do for a certain reason can impact speech. The other one I can think of is, have you heard of something called canine rises?

[Emma]
No.

[Jaz]
Have you heard of canine guidance?

[Emma]
Yeah.

[Jaz]
So canine guidance is, when you get the patient to grind left and right, the only teeth touching will be the lower canine and the upper canine. It’s a very convenient thing. Now, if you tell a technician, can you please design all these crowns, so that upper left canine, upper left premolar, upper left second premolar and the molar, everything is touching at once. Okay, so it’s very technically difficult for a technician to do that and for you to fit all these crowns and to be exactly like that.

It’s much more convenient to say, can you just make sure there’s one tooth touching the whole way along? Right? So we have all these things about canine guidance. I don’t want to get too much into the philosophy of occlusion stuff, but sometimes it’s very convenient to have canine guidance.

There’s lots of whole other factors as well. Now, if you lost canine guidance and when you grind to the left, right, you’re now in group function and you’ve decided that for one individual patient where you’re going to maybe increase the vertical dimension, do lots of complex sensory, that you want to give them canine guidance.

Again, if you just give them a normal shaped canine, it may not be enough. And so sometimes you need to augment that canine palatally and that’s called like a canine riser. You’ve kind of given it more material so that. It is steep enough, the angle is steep enough so that when the patient grinds, it starts hitting on the canine and that takes over the guidance. So this is when we basically design and deviate away from nature to try and give us a specific outcome that we design. In this case, an example I just gave you is a canine riser.

[Emma]
Okay. Well, so yeah, there is a few different examples there of where you would sort of deviate from the norm or what they may be with its pads when that tooth first came through. So that’s interesting, that’s interesting. My next sort of question, just more one that I’ve always thought myself, I don’t know if anyone else has, maybe my own notes from first year has helped me with this, but how do you tell the difference between a first and second premolar when someone’s had ortho, they’ve had a tooth taken out and the space is closed. I find that really difficult and I’ve had that in a patient. You just feel a wee bit silly when a clinician comes over and changes your chart and all the rest of that stuff.

[Jaz]
Okay, good question. For the lowers, by the way, it’s super easy, right? Do you know why it’s easy for the lowers?

[Emma]
No.

[Jaz]
Okay, from what I’ve seen in patients mouths over the years, tooth morphology is like a distant memory for me, like studying this. But one thing that always I remember is because when we’re crowning lower first premolars, it’s a challenge because the buccal cusp height is a normal position, but the lingual cusp of the lower first premolar is really lower down.

[Emma]
Yeah, yeah.

[Jaz]
The reason why that can be an issue is if imagine you’re going to do 1.5 millimetres occlusal clearance and then you’re removing 1.5 millimetres lingual cusp, you really have lost a lot of tooth structure in terms of percentage of height of that tooth basically. So if you’re looking at a lower premolar and thinking, hmm, is it a first premolar or a second premolar?

You just got to look at, is there a huge difference between the buccal cusp height and the lingual cusp height? If there’s a huge difference, easy, it’s a lower first premolar. If it’s less of a difference, they’re relatively even, it’s a lower second degree premolar. So that’s the one I got. Even I struggle, Emma, with upper first and second degree molars.

You know, if you look at a lot of the way the text has been written, it’s like, when you compare the two side by side, you’ll notice this. When you compare the two features, you’ll notice this, but when you just have one premolar, it can be difficult. So I would ask someone what difference will it make and why is it important that we identify this as a first or second premolar in that individual?

[Emma]
So, no. Is that a trick question? Does it matter?

[Jaz]
You hit the nail on the head, Emma. I don’t think it matters. Right? Because, you’re here now. One premolar was removed and so even I’m like first premolar or second. So, I would suggest that it’s not very clinically relevant in terms of which one’s missing.

The only time, the only one I could think of is, why it would be relevant is forensic dentistry, right? Unfortunately, someone has some sort of a funky way of leaving this earth and they need to now look at the tooth identification marks and whatnot and they’re not sure if it’s three different people and then they all had a premolar removed and then they’re saying, okay, well, this person had a first premolar it’s the only time I can think of it really.

Whereas actually in the real world, even having that knowledge of it’s a first premolar or second premolar, it’s not going to change anything that you do. But I know that the first premodels of the upper have got sharper anatomy. Like what I mean is that they’re more distinct, the difference in the buccal and the palatal once again, whereas the second premolar are a bit more similar.

But I couldn’t tell you more on that. I’d have to hit the same books that you got basically to help me identify it. So for your exams, guys, check out Emma’s notes so that you can nail it on the exam. But in the real world, trust me, you’re not going to blink an eye whether it’s an upper first premolar or a second premolar, whichever’s gone, good riddance.

[Emma]
Yeah. Yeah. And I think especially in your first year, if you have OSCEs in your first year, a lot of the time they’ll just give you a tooth that’s out of a head. I think it would be pretty cruel for them to maybe go for premolars, but you never know. You never know what they’re going to do.

[Jaz]
A common one, a common one I remember from an OSCE years ago, right, is an orthodontic OSCE is. They will tell you to chant the dentition of someone who’s like nine or ten years old or maybe someone with a retained deciduous second molar. Let me say again retained deciduous second molar because that baby second molar especially lower, it looks a lot like the first molar, and so sometimes you might confuse it as the first molar and then you might incorrectly identify the second molar in the wrong way. So that’s a common one, identifying the deciduous second molar and the first molar of adult dentition and making sure you get that right.

[Emma]
Yeah, definitely. That’s a good tip there. I think they love a good morphology in first year especially, so no, that’s a good one. I wouldn’t be surprised if I had something like that this year in third year though. Because we’ve done a lot of piece this year.

[Jaz]
That would be I think a very classic one actually. I think the top tip as soon as you know that’s a quite a common one I’ve seen in exams in general is and then that’s a skill they want to have not to confuse a baby tooth for an adult tooth and so which baby tooth looks very similar to an adult tooth is exactly that scenario.

[Emma]
Yeah or sometimes they’ll throw a hypodontia in there or something as well which is definitely a good skill that that you need to have been able to spot that. Yeah, lots of wee good tips and tricks there, but another question that I had, which the answer again might not be, oh, it’s not that important, but are there preventive measures or interventions, I suppose, that can address issues that relate to TQM and preserving natural tooth morphology? Like, is that something that’s important, I suppose?

[Jaz]
It’s a really, really interesting question, actually. So I mean, the angle that you’re coming from is how can we prevent where? Specifically, in relation to tooth morphology. So that’s interesting. So firstly, the first thing I thought of when you asked that question is generally prevention of tooth surface loss over time.

What can we do? And if you look at different materials and how they behave with each other, for example, the differential wear rates, so for example, if you take cobalt chrome and we take enamel, what if enamel is opposing cobalt chrome? How well do they interact with each other? Does the chrome absolutely destroy the enamel?

Or does the enamel destroy the chrome? Actually, polished cobalt chrome and enamel have very similar wear rates. They will really be good over time. However, if you have a chrome opposing composite, the composite will lose in a big way. So as they chew and grind and whatnot, the composite takes an absolute beating and will wear down, whereas the chrome will not.

So how is that relevant to your question? Well, enamel to enamel, it’s very similar. It’s the same material, right? So, actually, pure attrition, let’s say pure tooth grinding, clenching, tooth to tooth rubbing, if it’s pure attrition, it’s not going to be so damaging, right? Over time, yes, the teeth shape, the shapes will be very sharp and defined, and you see those wear facets, but it may not even go into dentine over someone’s lifetime if it’s just purely attrition.

The issue is we very rarely see pure attrition because of the abundance of extrinsic acid, so our diet, and intrinsic acid, so the single things like reflux and stuff. And so when you put a drop of lemon in the equation, that attrition really accelerates. Then you’re going to get into dentine and all sorts.

So the way to think about it is what’s your biggest cause of wear throughout life? It’s a combination of erosion and attrition. Of course, there’s toothbrush erosion as well, but that typically happens on the sort of gingival areas, not so much on the occlusal, right? So having said that now, what can we do to prevent it?

Diet advice. And for those, now we’re getting into some more occlusal philosophy is, if you set up someone’s bite right and in a minimally stressed dentition, when they grind left and right and stuff, everything’s in harmony, and therefore they’re not going to wear through so much. But, a simple thing is, people who wear retainers due to orthodontics, and they wear those plastic retainers, we know that their teeth will not change very much, right?

Because any grinding that’s going to happen, it’s going to be absorbed by that plastic and not by their teeth. And there’s these great dentists, like for example, a really famous dentist called Didier Dietschi, who shows 30 year follow ups of some of his composites at the front, which is crazy, right?

And then they look brilliant, but he actually says, okay, the reason why they look good, the reason they haven’t worn, It’s because my patient wore her night guard every single night for 30 years. Right? And so there’s a lot to be said about that. Finally, to answer that last point of question, which is the most important distinction, which is, okay, how does tooth morphology come into it?

If you have very delicate anatomy or very, let’s say, boisterous, voluptuous anatomy, I guess the best way to say it is Mamelons, right? If you’ve got mamelons, right, on your incisors, how often do you see people, right, beyond the age of, let’s say eight or nine with mamelons? You don’t, right?

[Emma]
No, no, not really.

[Jaz]
You don’t have mamelons, I don’t have mamelons, because it’s a very delicate, sticky, it’s a bit like, when you go to school, you get a brand new eraser, a brand new rubber, and then you start using it to rub some pencil marks away. You look at it and, oh my god, I’ve lost a huge chunk of my rubber already, right?

But then that rubber will last you until the entire primary school. You won’t get through it because the surface area of rubbing is so much now, right? So mamelons are kind of like that tip of the eraser. They’ll wear away like within a month, right? They’ll go from acid erosion, a bit of wear, basically they’ll go away.

But then the meat of the tooth will take some time. So how do we translate that into your question? Well, when we are rebuilding someone’s dentition, So you’ve got, let’s say you’ve got tooth wear. And then you’re going to open up their vertical dimension. Technically, we are now fully in control of the future anatomy.

We can wax it up any way we want. We can make the teeth look any way we want. Are we going to copy nature exactly? Probably not. Because having those delicate cuspal slopes, having those mamelons, having those very sharp canine tips, they’re just going to get worn away. So sometimes we go for like a age appropriate, right?

We get age appropriate. And we veer away from things that was going to just rub away or fracture basically. And so that’s a long way about saying is, yes, sometimes when you’re waxing cases up and it’s restorative, we’re going to not give someone a 10 year old’s incisor. We’re going to actually focus more on, okay, once that’s been worn away, what’s the main primary anatomy?

So I’m getting to, so maybe you won’t give the whole tertiary and the delicacies, You focus really on the primary anatomy. So if you guys can really focus, for the exams, yeah, learn everything. But for the real world, if you nail your primary anatomy, and then secondary anatomy, the most important one being line angles. Do you know what I mean by line angles?

[Emma]
Yes, I think.

[Jaz]
Emma, what you’ll learn is that if you ever say yes, then you have to tell me what it is.

[Emma]
So is this when, like, once you’ve cut a cavity?

[Jaz]
Okay. I see where you’re coming from. No, not in this context I’m coming from.

[Emma]
Okay, then no.

[Jaz]
That’s okay, and I want you to keep trying because line angles, I don’t think, is something that was in the textbooks, you know. Line angle is something I learned in a composite course and but it is actually tooth anatomy. Okay, so lateral incisors, right? If you look at them carefully, there’s a point where the labial sharply turns into the distal and the labial sharply turns into mesial. And if you follow that along from gingival to incisal, it makes like these two lines.

So these two line angles, these transition lines, basically. If you are doing anterior dentistry, so the next time you do a composite in the front tooth and you are the first one that you do, for example, I’ll say you, we should really brush up. And again, that line angle. In the right position, because if you don’t have that line angle.

Teeth look like tic tacs. Teeth look like flat blobs. It’s having those line angles which gives your incisors character and anatomy. So being really good at line angles when you start doing anterior dentistry is really important. And that’s something that is part of primary and secondary anatomy.

The whole tertiary anatomy stuff, no one ever shows it, it’s for Instagram. And definitely I wouldn’t go around making mamelons and stuff. And things that are, from an engineering perspective, if you’re treating a tooth wear case, you want to build it up for success and longevity. And although, yes, nature is beautiful, sometimes nature has elements where you don’t actually want to copy because it can be too fragile.

[Emma]
Yeah. And that did actually sort of tie in with my final question that I was written down, which was about if you have a patient coming to you, and they’ve seen your work on Instagram, but you’ve decided, this is a heavily worn tooth, you’re not going to rebuild it, like at natural morphology, is that a conversation you’d have with the patient?

Like, is that something that would be built into a consent form? Like, how do you communicate that? If they’ve got this expectation of walking away with a tooth that looks brand new, is as soon as it erupted, and they’re not going to walk away with that because it’s just not, it just wouldn’t be right.

[Jaz]
Emma, I’m really proud of you for picking that question. I think it’s a very intelligent question, okay? I’ll tell you why. It took me years to realize that when I’m removing an amalgam, right, which is invariably was a flat amalgam, right? I removed that flat amalgam, got my rubber dam on, I spent ages trying to think of the textbook and trying to work my beautiful anatomy.

And then I take my rubber dam off and I’m there for 10 minutes drilling it out of the biting end because it was too proud, right? And then it ends up looking like the initial flattened amalgam, right? And it took me years to kind of figure out what was going on. And so the mistake I was making there is I was trying to give this individual a tooth that was not compatible with the opposing tooth.

Because if you start with something flat. Then you’ve got to look at the opposing, and actually, unless you change the opposing as well, and then eventually, okay, you’ve got to look at the hole around the mouth, basically, if you’re trying to conform and keep the person’s bite roughly the same as it was before, then we can actually end up running late and embarrassing ourselves and losing control of the occlusion if we start to build all those natural cusps.

So, what I believe is, and it ties in well with the question, is we need to use the books and posterior tooth morphology as inspiration. Use that as inspiration. But what we give the patient will depend more on A, what the tooth looked like at the beginning before we started. B, what the opposing tooth looks like.

That’s going to actually slot into it and then how they mate together, how they fit together. And then that’s going to take precedence. You can still use like the outlines and the way you shape the angle. So it roughly looks like the kind of tooth, for example, when I’m doing a lower molar, I would kind of give it three buccal cusps and two lingual cusps.

I would do it basically. But they’re not going to be as voluptuous and as proud. It’ll be kind of, like, sometimes they can be quite curvy because sometimes they kind of be like chicken scratches that you put in with the probe, right? Because there’s no way that you can give that tooth anatomy and it still fit in that patient’s bite.

If you give a 60 year old, who’s got 250 years worth of tooth wear, and we’ll talk about that in a moment right here. So if you have a six year old who’s got significant tooth wear, a 12 year old’s tooth, it’s just not going to work on the bite. So, I think we should use the textbook as inspiration. So your question in terms of what do we actually tell the patient, if you have a patient who tells you that they want their lower molar to look like anything, run away. Run a million miles away from that patient. This is a red flag patient, okay?

[Emma]
Yeah.

[Jaz]
Usually, if it’s tooth color restoration, okay, and then they move their cheek out of the way and they have a look, they’re going to be over the moon, right? Okay. So, thankfully, we won’t have to worry about that story. Now, I have had a patient before, Emma, who came to me and she drew on a piece of paper what she wanted her contact points to look like between one premolar and the other premolar.

Like, I was doing her class two composite, and she drew for me what she wanted her contact points to look like, okay? This woman was nuts. All right? So, I’m not saying, you will get the odd funky patient, okay, and then maybe at that point you got to take photos, intraoral camera photos, like, look, I’m going to give you the best I can that’s going to fit into your mouth.

But I can’t make you look like Julia Roberts if you’re whatever, yeah, it’s my position basically. So your point is valid. But thankfully, that’s the posterior teeth, you know what, the patients are going to be okay, as long as it’s tooth colored, and they’re usually blown away by it, basically, in my experience.

But remember that the textbook for inspiration, but actually, what takes precedence over that is how it’s going to fit in that individual’s actual occlusion, which invariably means flatter teeth, less sexier teeth, and uploading it to Instagram when the rubber dam is still on. If you take the rubber dam off and do an adjustment, it’s not going to make it to Instagram, unfortunately.

[Emma]
Yeah, yeah, that’s the real world, that’s as far as you know.

[Jaz]
It’s the real world.

[Emma]
It’s not that good to know because you strive so hard to, in the second year I was carved an amalgams and polishing amalgams on the phantom heads and things and it’s just you go in the clinic with real patients and it’s just not how it is and that can be frustrating because you’ve learned all this perfect anatomy and you want to be able to replicate that but sometimes it’s just not applicable.

[Jaz]
What I don’t want to say is, I don’t want to sort of suggest for this episode that actually tooth quality anatomy is irrelevant because you’ve got to go with the patient’s own anatomy. I think it’s great for inspiration, and to get your restorations will look so much better.

If you get those three primary cusps buccally, tooth lingually, rather than just splodging something completely flat there, okay? To give some sort of anatomy is good. To have cusp tips and fossi does improve masticatory efficiency, so please do strive for it and it’s good, but you got to take a pragmatic approach and when we’re doing more like worn teeth and we’re rebuilding everything up, like you’re doing more of a full mouth kind of job, right?

At that point, you get to design it how you want. And so you want to design it with more natural anatomy, taking inspiration from the textbook, but you still want to design it in a way that if you don’t want to have too steep a cuspal angle, steep a cuspal angle.

Because a too steep a cuspal angle means that cusps will crash into each other. It puts more torsional stress down those cusps and whatnot. So it kind of needs to be minimally stressed at the same time. But the more you learn, if you want to improve your composites, if you want to improve how they look on posteriorly, if you spend some time to really study what tooth anatomy looks like, your composites will look absolutely beautiful just by positioning exactly where a cusp begins and where it finishes. Even though it’s a flatter one to match it, your composites will still look beautiful.

[Emma]
Yeah, no, that’s good. So take your books as your inspiration and go from there and see what sets in your patience. So no, that’s good.

[Jaz]
Absolutely. Brilliant. And what I would say is when you’re in the clinic, top, top tip is always check the occlusion before you start. I think we talked about it last time. Get a thin articulating paper. Don’t get the big fat blue wad because what’s going to happen is a patient might get the entire tooth goes blue. And you think, well, hang on a minute, where are the bite marks? If you’ve got a thin occlusal paper, you see a couple of few three or four dots, basically. And you’re roughly trying to copy that into your restoration. That will save you a lot of time and some adjusting away at the end, basically.

[Emma]
Yeah, yeah, no, that is a good tip. And it’s something, I did a tiny, tiny wee composite on lower central last week. But I did that before I checked the occlusion beforehand. It was an old one that had popped off or something, but no, that helps me because after, the patient’s occlusion was actually quite, like, almost edge to edge, and then the clinician came over and was asking about articulating paper and stuff, and you’ve got to grind that down, and I was like, oh, I checked it beforehand. And they were really happy with that, so I got a wee gold star there.

[Jaz]
Really good Emma, I’m glad our chats are paying off there which is great, and I think hopefully we can pass that on to everyone as well, which is great. Basic thing, but even dentists getting a bit in the real world, you’ve only got like half an hour or something to do a restoration, you’re like, okay, LA, quick notes, okay, let’s go in, let’s remove the caries, let’s do the filling, basically, but it makes so much, it will save you so much heartache, and basically it helps you take pride in your work, try and work with a degree of precision.

For to get it happy in the bite and to appreciate sometimes a tooth is not even in the bite. And then if you didn’t know that and you try and build it into the bite, but it was never in the bite in the first place, and there’s no real need to do in certain cases, that kind of stuff. That’s going to save you time as well.

So glad you emphasize that. In terms of next month, I’m just having a look with, oh, it’s crowns and onlays month. Okay. So Emma, I want you to think about some questions for crowns and onlays. I think we can actually make something really juicy here. I mean, there’s so many different ways we can go. And I will let you, as a protrusive, mains protrusive student, to suggest which notes would be good for the students and what clinical questions you want to ask me so that we can actually connect the students in the real world together, basically.

[Emma]
Yeah, good. I’ve not done, I’m not giving anyone a credit or anything yet, so.

[Jaz]
Have you covered the theory of it? Have you done it on phantom heads?

[Emma]
Yeah, yeah, we’ve done it on fansubhead and things, so I’ll cook up some good questions for that one, next one.

[Jaz]
Good, and we look forward to checking out your notes as well. So thanks so much guys, and I’ll just catch you in the outro. Thank you Emma.

[Emma]
Thank you.

Jaz’s Outro:
There we have it guys. Thank you so much for listening all the way to the end. Remember, we have the student forum section on Protrusive Guidance, which is something you can access on the laptop. protrusive.app or download the Protrusive Guidance app.

It’s on iOS and Android. And like I said, if you email [e-mail] with your proof of being a student, we will give you access to a little secret area, which is usually a paid for area, but just for students as a way of giving back, we’re going to make this happen for you. I look forward to growing this segment of the podcast with you guys, and thanks so much for all your comments and engagement on YouTube, as well as Spotify and of course, our Protrusive Guidance app.

Catch you same time, same place next week. Bye for now.