Onlays Vs Full Crowns – Decision Making 2024 – PDP189

Protrusive Dental Podcast

Have we fully shifted towards lithium disilicate overlays and onlays?

Are full crowns considered a sin in 2024? (Maybe just on Instagram then!)

Spoiler: Crowns TOTALLY have a place, and so do large direct composite restorations!

Dr Alan Burgin and I share our decision making trees for indirect restorations as part of ‘Crowns and Onlays Month’ on Protrusive Dental Podcast.

Find out which clinical factors sway us more towards a Overlay vs a Vertiprep – and the rationale for each type of restoration.

https://youtu.be/Gntb083yUOQ

Watch PDP189 on Youtube

Protrusive Dental Pearl: Use Vaseline on the gingivae when carrying out a ‘smile trial’ or bis-acryl mock-up – will result in an easier clean up!

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

Highlights of this Episode:
01:54 Protrusive Dental Pearl
02:44 Introduction – Dr Alan Burgin
18:20 Types of Indirect Restorations
31:16 From Onlay to Crown
44:40 Crowns – Traditional vs Verti-Preps
54:00 Reflection
57:48 Alan’s Prep Course

For the full educational experience, our Ultimate Education Plan gives you access to all our courses, webinars, and exclusive monthly content. This includes Vertipreps for Plonkers and clinical videos demonstrating Onlay Preps.

Join us on Protrusive Guidance, our own platform for dental professionals. No need for Facebook anymore! 😉

If you liked this episode, you will also like PDP089 – Vertiprep Revision

Click below for full episode transcript:

Jaz's Introduction: Overlays and onlays have become very popular. So is there still a place for full crowns? I still place full crowns because I use vertical crowns, i.e. vertipreps. Even then, if a tooth has enough enamel, my indirect restoration of choice will very likely be an overlay restoration. Something like lithium disilicate.

[Jaz]
The other modern consideration that we have is composite. We can actually go really far with composites and I know the bigger the composite the less predictable it can be but sometimes with modern techniques and looking after the occlusion you can get a long time out of a large composite and often due to budgetary reasons or otherwise the large composite is what we may be opting for in many scenarios.

So where do we draw the line? What’s the limit of a large posterior composite? These are all the real world questions we’ll be discussing today with my guest Dr. Alan Burgin as part of crowns and onlays month in June 2024. So remember in February we did Adhesive Dentistry, then in March we did Documentation, April we did Mental Health, in May we did may the Force Be With You Orthodontics, and now we’re doing Crowns and Onlays. And I hope you agree that this is big enough to deserve its own month. It’s our daily decision making. It’s our bread and butter daily restorative dentistry.

Hello Protruserati, I’m Jaz Gulati and welcome back to your favorite dental podcast. Every PDP episode, I give you a Protrusive Dental Pearl, except this time I’ve actually just run out. There’s no more pearls out there. There’s no more tips. In all the episodes we’ve done in the last six years, we’ve covered every single tip in Dentistry. And so, there we are. There’s no more tips, guys.

Dental Pearl
I’m just kidding. Listen, the tip for this one, the Protrusive Dental Pearl, by the way, if you want access to every single protrusive dental pearl, we’ve created a new PDF, by the way, which all the previous pearls are there in one PDF. This is freely available in Protrusive Guidance, our community, and the home of the nicest and geekiest dentists in the world. The website for that is protrusive. app or download the iOS, Android app is called Protrusive Guidance.

The pearl for today is when you’re doing a mock up with a bisacryl. What’s bisacryl? It’s like, you know, ProTemp, LuxaTemp, Integrity, all these instant crown bridge temporary materials. When you’re doing a mock up like a smile preview, perhaps before veneers or something. The issue we have is how ugly they can look because of how much coverage they get on the gums. Now you could try and scallop the putty so that it’s less messy and less on the gums. But a really important tip I’m going to share with you is to put some Vaseline on the gums.

I literally just get Vaseline all over the gums and it’ll be so much easier to take off that bisacryl. So you get that really crisp, beautiful look of that mock up. So next time you dive straight in to put that putty on, just remember a little bit of Vaseline goes a long way on the gums. Now, I hope you enjoy the conversation with Alan, which is eligible for CPD via Protrusive Guidance. And I hope you enjoy our little geeky discussion. I’ll catch you in the outro.

Main Episode:
Dr. Alan Burgin, the Bergmeister. This is like, I don’t know, your third or fourth appearance on Protrusive, but let me tell you, man, you’re always such a welcome guest. How are you today?

[Alan]
Yeah, I’m good. Thanks, mate. Thanks for having me back on.

[Jaz]
You’re just such a great guy to speak to. And I know one of the fears I had, Alan, about having you on the podcast again, let me tell you a fear I had, right? The fear I have is that we’re just going to be like two guys just totally in agreement with each other. And it’s going to be very vanilla, right? Now, it’ll be still very educational, and it’ll be totally worth everyone’s time to listen about it and gain something and our philosophies and what we consider when we look at an individual tooth in a mouth and figure out, okay, what type of restoration will I choose?

And I think there’s a lot to be said about that. And everyone’s different, but I’m scared that it’ll be too similar. So I’m going to be really trying to play devil’s advocate and try and find some differences, which I’m sure hopefully we’ll find one.

[Alan]
Yeah, that’s fine. Maybe I’ll try and chuck some curve balla in there for you so I can catch you out.

[Jaz]
Maybe, maybe I’ll start challenging you. But for the listeners, those who haven’t heard any of the previous episodes with Alan and also for those that are premium members, he’s got a really great full mouth rehab sort of walkthrough, which was just truly brilliant. That’s on the app, but the previous episodes are done. Do check it out. We talked a lot about initially we talked about the career journey and then what did we pivot to thereafter?

[Alan]
We did a Gothic arch one, didn’t we? I think we’re on YouTube. That got really, really nerdy.

[Jaz]
Yeah, that was really geeky. Centric relations records and everything that was with Chris as well, wasn’t it?

[Alan]
Yes. Yeah, yeah.

[Jaz]
I’ll put the show link in the show notes. I’ll put the link for that as well. Today we’re talking about when do you crown something like a full crown? And nowadays, when can you consider doing more like an overlay onlay? And we’ll discuss all these terms. But before we get into that, for those who haven’t listened to us previous episodes, Alan, just remind us, you know, where do you practice? What is your niche? What are your passions?

[Alan]
Yeah, sure. So, I’m based down in Cornwall. I work in the city of Truro, which is just about classified as a city, as big as it gets in Cornwall really. I work in a fully private practice and I’ve been placing implants for probably last five, six years. But my main area of focus, similar to yourself, is more tooth wear related.

So I’m very much a general dentist. And do everything pretty much apart from endo and that’s what I like to do. Yeah. Bring it all together. And I like having that background with the implants that fits quite nicely with the tooth wear. And yeah, mostly focusing now on rehabs, indirect, direct as well. And those bigger cases where you can, like they would say, play that quarterback role on.

[Jaz]
Well, I see your Instagram, I follow you, I love the stuff that you do. And the thing that you’re great at, which so much of the Protruserati guests that we have on are so great at, are really reflective posts and step by step stories and considering and rationalizing the daily decisions. We have to make those bread and butter decisions, but you truly are a great generalist.

I love how you are. I don’t even say you’re jack of all trade. I truly think you’re in that category where you’re getting the master of all trades or aspiring to be. And it’s so great to see all the things you put out there. So please continue to do that. Today’s topic is such a real world topic, right?

We deemed a tooth to need an indirect restoration. Which way will we go? Will we prep 360 degrees around the tooth or are we going to be a little bit more contemporary? I’m going to do like an onlay or an overlay. Now, before we even get to that, I think the first place to start, Alan, I’d like to hear your views and reflections on the following question.

Nowadays with composite, we can really push the boundaries a lot more like the opportunity to do a M O D B L like all surfaces composite, kind of like a direct onlay is looking a lot more predictable than it was perhaps in the past. And a lot of times we are, we are doing this as our, definitive restoration. So I want to ask you, how do you feel about composites getting bigger and bigger and bigger? And at what point have you drawn the line in the sand that now in 2024, this is the point where you’d be happy with that composite. This is the point where you think, actually, no, I’m not going to even get the compules out here because this tooth needs an indirect.

I’m just going to put a core in there or tell the patient it’s a core, but really this patient needs an indirect. So essentially what is the boundaries? Where are the boundaries of large composites.

[Alan]
Good question. It’s really relevant, isn’t it? Because that’s the kind of stuff we see in practice day to day. I always try to be not overly negative, but I will often give patients worst case scenario. And you know what it’s like, sometimes you look at a tooth, like this definitely needs. And others very obviously, an occlusal that’s fine. We can just go direct, anything that I’m looking at.

And I’m looking, there’s a bit of a thin cusp. I’m a bit, maybe I’m going to lean them towards saying, I think the indirect would be the best option here. I was not necessarily using those words, but for me, that line in the sand, it’s a bit of a wavy one, really, because I think it comes down to two things.

You’re right. As materials and mechanical ability of those has improved, it’s not really just about how good the material is. The other factors, things like time, anatomy, contact point, those things haven’t really changed. And so it’s a combination of that like real world approach. What is going to be working data in day to day practice, because at the end of the day, like you’ve said many times before we are in a business as well as a healthcare and if you’re going to spend more time creating a less ideal outcome, it’s not in anyone’s interest.

So I would say from those like technical aspects, contact point, proximal contour, I’ve said anatomy, that’s going to lead me towards that indirect if I’m on these larger restorations. I had a case recently where it was on a periodontally compromised patient, upper seven, they had an eight, and they had this really deep, really wide cavity.

Pretty much both the distal cusps missing. I said to them, okay, look, this is large. We could do a filling, and I quite often will say to them regardless, I say, technically we could do a filling, but we’re really stretching the limitations of the material. A better option might be this. And I cleaned it all out and I was looking at it and I was thinking, okay, this is getting pretty deep.

It’s really wide and deep. I think I could do a filling. But should I? And then as I finished cleaning out the caries, I found that it was, because of the perio and the depth of it, we’re down onto the root surface, we’re sort of into that furcation there, and you get this concave margin. Okay.

[Jaz]
The dreaded concave margin.

[Alan]
Yeah, yeah. I mean, it was the holy triad. It’s like, concave margin, wide and deep like, purely for the ability to make the shape that will restore this. This is better done indirect. Forgetting because we say-

[Jaz]
And also like you mentioned on this already, the time aspect you mentioned, and then to restore that, like, cause you’re super skilled, like I haven’t, you won’t say it yourself, but I can tell you guys, Alan can do this, right?

I have no doubt, Alan’s one of the very few dentists. I let my own mouth and do a large restoration like this. So I totally know. I’ve seen that Alan can do this. He’s got all the tricks in the book, the PTFE in that concave area, modifying your matrix, trying to get the good contact, but it will still take you a lot of time, right?

Because you can’t rush these things, right? So all that time you’re putting in, if you were to truly charge your hourly rate and then you’re thinking, I’ve just charged someone a significant amount of money for a direct composite, where perhaps an indirect will last better, produce a potentially a better contact, better longevity for a similar price, maybe not too much more. That’s also going to come into it.

[Alan]
Yeah. And I think it’s nice to have the skills in your toolbox to do it from time to time. If you feel you need to, or you get into one of those positions where you go, oh, this is worse than I thought. I haven’t really warned the patient about this. I need to do a composite. But at the end, I’m going to say to them, look, next time around, this tooth needs something doing. It’s going to need crown on there or whatever.

[Jaz]
And that’s a very real world scenario. It happens, right? It happens.

[Alan]
Yeah, for sure. For sure. But equally, I will, like I said before, I’ll sort of give them worst case scenario. And sometimes those on the fence cases, I will say to the patient. This appointment is going to be to deconstruct the tooth and commonly things like if you’ve got crack and whatever, it’s a really useful option to not sell yourself down this one treatment option and say this is a hundred percent, what you’re having today. It’s like with the crack you open it up you go okay, actually, this is way worse than it looked we need to cover these cusps or worse even worse going to the pulp So it’s sometimes nice to just leave a few options on the table and say, look, this is an investigation appointment, especially when you start getting into the bigger cases for now.

And you’re going, we’ve got a lot going on here. You can’t stay in the chair and be numb for two days. So we’re going to just break this down a bit. I’m going to investigate. Like you said, put some calls in. getting stable, then I’ll give you a definitive decision once we know exactly what we’ve got.

[Jaz]
I think just homing in on, I mean, there’s so much we could talk about, but if you’re homing on the single tooth issue first, and if you pitch it as an investigation appointment, but make sure you charge appropriately.

So, if an hour, for example, right. So if you say a hour, you charge your hours fee and the patient knows it’s an investigation. Now, once you deconstruct anything, actually I can do a direct here. You will do the best direct you can and take some photos and show the patient. Okay, I think we’re good.

I think we’re good for many years. Look after it and I’ll make sure we look, we do our job as well. But if you’re halfway into that appointment and you think, okay, this tooth will definitely need an indirect, then you can at least put a core in. You don’t have to put as much emphasis on the anatomy as long as you get the seal.

You want to get the seal here and you want to make your life easier for the future. That’s a good point to maybe start planning and having that discussion and make sure everything’s in order, but the patient’s already been warned and explained that this will need additional treatment and you could take all your intro or camera photos and explain why we’ve done a core, a foundation restoration and you’ve had that chat ahead of time.

[Alan]
Yeah, absolutely. Yeah. And then when I’m doing the crown anyway, I’m going to charge for the core. So it’s more like just breaking the appointment into two really. So, on that stat, if I knew I was definitely doing a crown. The first bit is take out the old amalgam and the bit of caries anyway, and then put a core in.

And there is some level of charge for that. And so, in these, like, uncertain scenarios, Really, you’re just breaking the appointment into two, and perhaps it might work out a touch more expensive by doing it that way because there’s some overlap with the LA and rubber dam, whatever, but they’re gaining certainty or improved predictability on what your outcome is going to be.

[Jaz]
Yeah, especially if you’re unsure on that one, then there’s a good way to go. And sometimes, you probably experienced as well, Alan, like once you see some things inside the tooth that aren’t very pretty, and then now you’re doubting the pulp or prognosis at that point, you might actually leave it as a foundation restoration, but the best seal and even actually go try your best to get a good contact.

So you’re kind of doing a long term direct restoration, which is pushing the boundaries and limits of the composite, but you’re doing it with intention of a period of monitoring, careful monitoring. And again, the patient is informed with the pathway that, okay, we’re going to give it X amount of time and we will reassess for an indirect restoration. Is that the kind of thing that happens to you as well?

[Alan]
Oh, a hundred percent I’m a big fan of a test run and a month increased monitoring phase on any indirect like that. Sorry, where we’ve got any sort of questionable hopeful situation. So we work in private practice, people come and they pay good money because they want a good quality outcome.

And so if we can build predictability into that, I think that’s really important and valuable for them. So quite regularly, I mean, yeah, I did it this week. We cleaned out, they were having a crown, a vertiprep crown, which I’m sure we’ll come on to, and I prepped the tooth and it was way deeper than it looked and it was right, one of those ones where it’s right on the surface and you sort of taking your hands and instruments and just scraping away over the way big the pulp is trying to be careful.

And so at the end, all was fine. I put the temporary on and I said, look, we’re going to leave this a few more weeks. In that case, I’ve got the scan. I’ve got everything sorted. I’m not going to send that scan off to get processed. I’m going to book in a phone call in two weeks time, see how everything is.

And nine times out of 10, it’s absolutely fine. But, if you didn’t do that, you’d be getting that phone call two days after you fit the permanent crown saying, I was up last night and it’s a bit sore as you’re getting up. Why did I go to Zirconia and have to drill through it?

[Jaz]
We’ve all been through it. But you’re trying to be a bit safer in doing it in a phased way. Just a reflection on longevity of composites. If you look at Nick Opdam’s studies, which I’m sure you’re very familiar with, longevity of composite being 82 percent at 10 years. And in that study, they found that the two most important factors for the success of the restoration was A, the patient’s oral hygiene and B, the extent of the restoration.

The more surfaces involved, the less likely it was going to make that 10 year point. And so we know that the bigger it gets, the less predictable it gets in the long run. But when you look at the complications and the failures, so of those 18 percent that failed at 10 years, if you look at what the mode of failure was, initially in the first year, the biggest failure was endodontic, pulpo flare ups.

If you look at the second year, it was again, endodontic. Then third year, the fractures, fourth year fractures, fifth year fractures, and then the caries comes a bit later, basically. So the most common two reasons was caries and fracture, but the initial failures were endodontic. So if it’s going to flare up, it’s probably going to flare up in the first two years, and so I use that as a guide, basically, if I’m unsure and I’ve got that large composite and it’s got a nasty crack inside and I’m debating, I was unsure about my sensibility testing.

I would sometimes say, okay, and I’m happy with the contact achieved. I must be happy with the seal and contact achieved. I’m happy with those two. I say to my patients. Let’s keep an eye on it for a couple of years. But they know that the next step here is a crown, just like yours. The other reflection I have, Alan, before we start talking about the time, when we are actually committing to indirect, right?

And I’ve never seen this anywhere. I feel as though this is original from me, but maybe you’ve heard it somewhere, is the guy or gal who decided to put how many of a grams of composite in as a compule, right? They kind of said, okay, we’ve got to put the right amount of composite in a compule to actually fill most teeth.

And so if you’re finding that very regularly, you’re having to reach for that second compule, then maybe you need to commit more to decide that actually it’s time to go indirect. So the more times you’re using two or more third compule, like very rare, and it really shouldn’t be happening, right? But if you’re stretching the limits of one compule, it’s another, one other factor to consider that maybe this composite is getting too big and maybe I should be considering indirect. Have you ever come across that or thought about that?

[Alan]
I’ve never thought about that. I think that’s an interesting point there. It’s good to like, have as a yardstick, I suppose, in the back of your mind. Yeah. I think if you’re definitely on those, onto three compules, yeah. You’re stretching it for sure. And I think with the introduction of bulk fills as well that can potentially start to stretch maybe the size of the composites you become more comfortable with. But yeah, I don’t regularly go over one compule. That’s a good yardstick. I like that.

[Jaz]
See, that’s a good sign. See, if you don’t go regular one, you’re respecting the material. And I think if that’s one thing extrapolated from Nick Optam’s studies that he’s done both retrospective and a systematic review. So that was great.

I love that. So we’re definitely in agreement with that, which is a real shame. We haven’t disagreed on anything yet. Okay. So this is a bit where it might get a little more fun. Okay. So. We’ve decided that actually this tooth, whether it’s after the investigation or you just look at tooth and think, okay, this definitely needs cuspal protection and I’m really stretching it my composite.

We’re going to go indirect. Now, maybe the best place to start here is instead of thinking, what are you thinking in terms of what type of indirect restoration? Let’s talk about tooth. As an overview, what type of indirect restorations that you have under your skill set that you use and what percentage of the time are you going, for example, onlay overlay, what percentage of the time are you going full crown?

And then maybe we can branch out later. But in terms of the types of indirect you’re doing, what are the percentage breakdowns roughly?

[Alan]
Sure. So I think that this is probably best answered on more of a toothbasis and in general on the whole mouth, cause I would say on a molar, I’m probably more like 80 percent onlay or overlay, like bonded and yeah, maybe 20 percent crown, but on a pre molar, it’s probably closer to 50 50.

[Jaz]
And so what are the determinants of, just let’s talk about the difference between molar and premolar. Why is it that your percentage is so significantly different?

[Alan]
I think it’s because the remaining tooth structure on a premolar often ends up being less, an MOD amalgam is percentage wise, it’s a lot more destructive on a premolar than a molar when you take it all apart.

So I often find I’ve got less tooth tissue to work with. Combine with that. You’ve got the whole aesthetics element. So, upper four, for example, you are going to get caught out if you start leaving onlay margins mid buccal. So that sways it a little bit. So I would say about on balance aesthetics combined with two tissue remaining once you’ve removed the old restoration.

[Jaz]
I also find that premolars with their shape and their cusp incline is very prone to cracking. And when they crack, then you’re dealing with that. And then that often may go subgingival. And so that’s a great point. Unfortunately, again, I agree with you. That’s the same in my experience. I’m being more.

Full crowns, unfortunately, a higher percentage, totally agree. But you know what? When I’m doing an onlay or overlay in case of premodelers, I’m doing like a von lays, veneer on lays, right? Because I want to get that sort of a facial, obviously the patient to patient aesthetic demands and whatnot. Some people will just not accept that mid buccal, however good you are, however amazing you are and hiding that, that margin.

For some patients, for safety, you just want to right over the buccal and it’s kind of like you’re veneering, you’re staying within enamel and that tooth needs an indirect restoration. Anyway, I don’t think you’re really weaking the tooth that much.

[Alan]
Yeah, absolutely. And I think I used to quite, not struggle, but I used to be maybe a bit slow with the veneer lay because I would do an onlay, look at it as in an onlay preparation, look at it when I’m near the end and go, I’m not sure about that margin, whereas now I feel like I’m probably a bit more pragmatic about it.

And I look at it and I go, this needs a veneer-lay. So I’m prepping a veneer-lay from the start. And I think anytime you have that indecision in your mind about two procedures, it really slows you down massively. And so it’s like anything, isn’t it, that we do, if you not only have a diagnosis, but also a plan of what you’re going to do and how you’re going to do it, it’s going to just be a smoother ride all the way through.

But yeah, definitely. I’m quite keen on the veneer-lay, the main like deciding factor for me on the premolar there which cusp is it obviously. Right. But if it’s the-

[Jaz]
So you just expand on that. Yeah.

[Alan]
So say you’ve got a big MOD amalgam and you take it out and there’s like a bit of a crack going underneath the buccal cusp. Okay. I’ve got to cover this cusp and it might be that the palatal cusp is, say it’s a bit thin, but you’re going to cover it. Okay. Perfect for a veneer-lay. You’re going to cover the whole occlusal surface and overlap onto the buccal. If it’s the palatal cusp. That’s a problem. And I’ve decided that I’m going to cover the buccal cusp as well because it’s thin.

Then I’m leaning more towards a vertical crown because it falls into that same category as well as talking about with the decision between composite and ceramic. It’s like I could do it, like I could take the time to do this, but should I? And what is actually best for the patient mechanically? And how many prisms am I saving for this potentially more complex and in more complex, you get potentially less predictable situation.

[Jaz]
So what we’re saying is a tooth that’s more structurally damaged, particularly the functional cusp by the palatal cusp for premolar. If you’re finding that it’s getting less tooth tissue, then you are more likely to go for a full crown. Now you mentioned vertical crown. We’ve got to have that discussion about horizontal versus vertical.

We’ll come onto that, but let’s just go with a basic thing that at dental school, in my training, and it’s probably very similar to yours, Alan, because we qualified at a similar time, is I was not really, I never did an onlay at dental school. We were prepping PFMs and full ceramic crowns all the way around, 1.2-millimeter shoulders all the way around, and then only through external courses and seeing the light of adhesive dentistry, and I’m the same. I mean, most of the default restoration would be, it’s got to be an onlay if I’ve got enough enamel, and we’ll talk about the decision making basically.

But the times that I’m doing brand new crowns, it’s more likely when I’m replacing an existing crown, or there’s going to be a really good reason with the reason we come onto that I’m going to cut a crown. Because basically, just like you said, we are trying to do an onlay or an overlay in ceramic because it’s a very good restoration to preserve the cervical third of tooth and preserve enamel and it’s a decent dentistry and it’s fun to do and it’s all that kind of stuff.

And we know that adhesive dentistry can be so a preservative tooth structure. So my question to you is, did you find the same thing in terms of, you did crowns in dental school, but then when you came out through courses, you were doing less full crowns, and then you pivoted more towards on lays, overlays, only because of the external education that you received?

[Alan]
Yes, so continuing on our veneer-lay tone of agreement, that’s basically exactly what happened to me. But I will replace your external courses with the school of Facebook. And I often tell this story of people can often relate to this, that exactly the same as you. I was a few years out, I was doing crowns.

I was quite happy with crowns. And then I started seeing all these onlays posted online. Okay. This looks like modern day dentistry. It’s all over Facebook. I should definitely be doing this. So yeah, you look into it, you find out about what it is. I remember having this patient in and they booked in for a crown and I thought, not today.

You are getting submittably invasive adhesive dentistry. Prepped for an onlay and it went fine. And then a couple of weeks later they came back, may or may not have had the temporary on at that stage. And I popped the rubber down. I was like, okay, we’re going to bond this in place. And I got about two minutes from the end of the appointment, and I looked down and I was like, I’ve got about 50 percent of this appointment left to go.

And I was so late. So it was pretty stressful. Get this thing on the tooth, get it bonded. I ran about 15 minutes late. And then, it’s like you try something new. It doesn’t go particularly well to plan. You sort of have your tail between your legs for a few weeks and you think I’m going to do this again.

Did the same thing again, but I added 15 minutes to my fit and it was fine. I probably did a completely different style of onlay prep and it was, but it was still a bonded onlay and I had bit more time.

[Jaz]
So just to clarify, this is lithium disilicate, Emax, that kind of stuff. Just so those people understand what materials we’re using.

[Alan]
Yeah, sure. So this is lithium disilicate, Emax onlay. And then I found myself in this like kind of ethical dilemma where I’m looking at teeth thinking this is going to take me more time to treat this tube of an onlay. And I feel like it’s the right thing to do.

And I can’t really, it’s an awkward conversation to say to the patient, well, I’ll charge you a bit more for this because it’s better for your tooth. But it just takes me longer. So I was charging the same price. And then, you’re trying to justify whether a crown or an onlay with these like additional ethical financial thoughts.

And so then I basically just came around to the fact that these are quite different procedures. And the prep is going to be where I save a bit of time because I’m going to need that bit of extra time on the fit. So that was kind of my pathway through it. And then, yeah, once I found that could have that completely take away that decision factor of I’m just can now decide on what is what I believe to be the best treatment for this tooth. There’s no time, there’s no financial second thoughts. It got a lot easier and you could really start to do things.

[Jaz]
Well, I love that you said that you save more. I mean, once you get a bit of experience, yeah, you definitely, it’s a quicker prep, right? You dismantle the MOD amalgam, you clean out the caries, you reduce the cusps, and you just make it flow all the way around.

I know I’m simplifying, oversimplifying it. You’ve got to reduce, fill in the undercuts and immediate dentine sealings, blah, blah, blah. We’ve got loads of episodes on that. But that can be quite slick, especially in a rubber dam. It’s a beautiful thing to do. It gets a bit more complex with deep marginal elevation.

We’ll talk about that at the end, I think, because that’s where it gets a little bit heated, right? So we’ll talk about that later. But the fit appointment, yeah, it takes a bit more time because again, you’ve got to isolate, you’ve got to do your prechecks and isolate and do it under well isolated conditions, but it’s very rewarding to do it. And the amount of tooth structure you’re saving is great.

[Alan]
Quickly, just to come back to what you were saying before about that, the mindset after university, and you’ve been doing these pretty heavy preps, 1.2 millimeter margin. I think obviously that you see a lot of debate online. This like the whole title of this topic on those versus crowns, right?

And I feel like people are having different arguments because you’ve got someone going, well, a PFM with a 1. 2 millimeter margin versus an onlay, it’s a no brainer, and in terms of which is more destructive and whatever, compared with, say, someone who is doing a different style of prep, a more minimal crown prep, and they’re going, well, I think there’s a bit more balance to this.

And my colleague, Colin, Colin McGuirk, who I work with on the prep course, it’s not out yet. You’ll like this. This is some stats for you that are hot off the press. Right? So, there was a study a few years ago where it looked at PFM and the biological cost, right? So the tooth removal was between 65 and 73%, right? So what would expect for a PFM? Mega destructive.

[Jaz]
Is this the Edelhoff study? Is that his name?

[Alan]
I think so. Yeah. I can’t remember the title. I’ll look it up for you. And so, and then they compare that to an onlay, and the tooth reduction loss for an onlay was 32%. And so that’s where that crown onlay argument.

Yeah, makes a lot of sense. So then what Colins looked at is he prepared for first of all, a BOPT style VertiPrep. So that is a deep preparation where you’re going very sub gingival, you’re effectively turning the tooth into a cone, no undercuts. So of the types of two types of VertiPrep there are or so, the more aggressive of the two. Okay. Biological cost was 45%. So way down on the PFM. It’s still not quite as good as the onlay, and then he looked at the shoulderless. So the butt bur start, and that came in at 31%.

[Jaz]
Oh, wow. Doesn’t surprise me, but it’s nice to have these numbers.

[Alan]
Actually, it doesn’t surprise you, but it kind of makes that up. You go, hang on. These are completely different arguments. You know? PFM compared to a shoulderless butt bur prep on upper six. It’s like and the nice thing about those stats is. Again, takes away that feeling of the old, am I naughty if scenario? You’re not naughty if you’re going to be doing this shoulderless prep. So, and I’m sure that’s what you found, when you do those preps, you look at the tooth, nice, that’s great.

[Jaz]
Unbreakable. There is no chance of this crown coming away with a core in there. Like there’s zero chance, right? And so that’s why it doesn’t happen. I mean, just photographically, if you’re a newer clinician or maybe your clinician is still doing full crowns, like one millimeter shoulderless all the way around, and you haven’t really embraced the adhesive world, you might go on social media and see these images of like tabletop style onlays.

And you might think, whoa, actually, when you look at it from the buccal view, you think, whoa, there’s a huge volume of tooth structure lost here. And you think, how is this more preservative? Or if you think about it, Once you strip out that huge MOD amalgam, all you have to do is remove the cusp by two millimeters and polish it around.

And that’s really what’s left. So really, an additional tooth structure has not been removed. And the part of the tooth that’s been preserved is a cervical third. The entire foundation of a tooth comes from cervical third. So that’s something that we should always bear in mind, that’s how it is advantages.

And I love that you had those stats, actually. I love that. Now, before we talk about the whole vertical preparation, just give us a guideline that when you’re looking at a tooth, let’s looking at a molar, what are the factors that are, you know, if 80 percent of the time you’re doing, you know, ceramic, lithium disilicate, onlays or an overlay.

So onlays being replacing one cusp, at least an overlay replacing all cusps, just to make sure we’re on the same terms here, what is going to deviate you away from the onlay and more towards a crown? And then the last part we can discuss about, okay, the crowns, horizontal versus vertical, but why onlay? And at what point does that onlay now become a full crown?

[Alan]
So you can break that down to three things really, okay? Aesthetics, isolation, and enamel. If you can get all three of those. And when I say aesthetics, it’s like, does it matter? So lower six is different to an upper four. Because no matter, we do lots of things.

We bevel our margins, use heated composite and blend over the line. We do lots of things to try and minimize that. But ultimately, that’s the sacrifice that you are going to be making for saving.

[Jaz]
Just to clarify, the onlay overlay, it has the danger of being less aesthetic than the full crown, just to make it clear, because the crown is covering that entire buccally, a lovely gloss. Whereas even the most seasoned clinician, there’ll be a line often, you try your best and everything, but there is a gradient, a change from the restoration to the tooth when we’re dealing with overlay and onlay restorations.

[Alan]
Yes, exactly. Yeah. So aesthetically, is there a concern? Isolation. So we’re talking about bonding here, and all the success comes from how well is this thing going to stick. And there was another really interesting study where they looked at this over four years, and they compared inexperienced with experienced clinicians on their success rates have bonded onlays and what they found over this four year period was that the experienced clinicians had about a two and a half percent failure rate, which is pretty good.

[Jaz]
And how many years?

[Alan]
Within four years.

[Jaz]
Four years, four years. Okay.

[Alan]
I still think that’s kind of high, but anyway.

[Jaz]
I know, right?

[Alan]
But the inexperienced clinicians had about 26 percent failure rate. Well, I sort of drew from that. And this is like kind of the way we teach is that you want to have, there are some things you can’t cut corners on. And that is the bonding. Like that has to be a meticulous process, but the actual preparation, we don’t want to make it so complicated that you have to become an experienced clinician before you actually get any success rate.

But whilst you’re inexperienced, you’ve got to make most of that 75 percent success rate. So the focus there is you’ve got to be able to get the isolation. So that you can get that meticulous technique and bond it properly. Otherwise it’s just not going to work.

[Jaz]
My immediate thought on that study was that perhaps the experience clinician had better case selection, which is exactly what we’re talking about now, right? When you have, when you can isolate it for sure, and I said it well, and you’re just about to come onto when you got enough surface area of enamel, which is what you’re relying on, like an onlay and overlay, it does not strictly speaking have retention form. If you can pull it off vertically and therefore it doesn’t have a retention form.

You try and want to build in some resistance. So I try and sort of tip it over with my finger just off the prep. Can I go sideways? Will it tip off? And ideally, I don’t want to see it tip off because then you’re more towards a flat tabletop. And we’ll try and not do that. If we can try and get some follow the sort of sinus anatomy of the tooth kind of stuff.

So I think the huge bearing is case selection because that experienced clinician has burnt their fingers and thought, you know what, there’s not enough enamel here, and I’m probably going to go for the crown. And then we could talk about the vertiprep and the benefits of that, as we already mentioned too. But do you think that is one factor that we can draw from that study?

[Alan]
Yeah, I think it’s definitely going to be a combination of the two, isn’t it’s going to be decision making combined with your actual skill set to perform the restoration. So I definitely, I think it’s like you said before with GDPs, pick out low hanging fruit with cases and being cherry picking what you want to want to do.

It’s the same as like, you’re looking on on a pick out a sure winner, then that’s going to make the rest of it. And then yeah, the third point was yeah, enamel, like we just touched on. So you want to get that enamel bond and that is what is going to ultimately give you the long term success. The more enamel you’ve got, the better it’s going to be.

[Jaz]
What’s your cutoff point? What’s that line in the sand for how much enamel Alan needs? If he’s going to do an onlay on his mum, how much enamel do you want?

[Alan]
Onlay on my mum? Maybe, I don’t know, I might get a referral. No, do you know what? I’ve fallen into more and more family dentistry over the years. I’m awful at saying no.

[Jaz]
But you know what? We should record a whole episode. And one of my colleagues and friends, Susie, she’s got some great stories about treating families. One of my colleagues, Maria, she’s got some the shit always hits the fan when you treat family, I find, right?

Just because you got your guard down and I think there’s to be so many great stories from the Protruserati about treating family that on the app, we should probably start a thread about tell me something funny that happened when you treated family. It’s just, it’s a no go for me. I really try hard not to treat family.

[Alan]
Oh mate, get me on that episode when you do it. It’s a story for another day, but oh god, yeah, I’ll be on there. I’ve got some stuff on that.

[Jaz]
But what’s the goal? How much enamel do you want?

[Alan]
I’m going to, so this is not evidence based. This is from what we routinely see as a good sort of experienced clinician opinion, basically, and it’s around 75%. Effectively, if you’re doing deep margin elevation on the mesial and the distal, and you’ve got a bit of dentine on the deep buccal because it’s down the cervical area, like stretching it.

[Jaz]
And just for the students who might be listening in, what is deep margin elevation? Just to make sure we cover that. Not too extensively, because that could be a whole episode, but just the principles.

[Alan]
You saw me, you saw me, my brain was going there into a deep session starting. Basically, when you drill out old filling and decay, the margin will stop at some point. You have two options. If that margin is very deep, You could either drop the tissues down, so they are below the margin, so that would be with something like crown lengthening or a papillectomy.

Or you can lift that margin up with composite, and you are then finishing on that margin of composite. A little, like, nod towards that. So this is not brand new, okay? It’s one of those things that I think is the same as with Vertis, right? Which you might come on to. It’s a procedure that’s been sort of rebranded.

So it used to be, I actually called it cervical margin relocation 1998, I think. And then it was called proximal box elevation and then deep margin elevations. Well, yeah, man. Yeah. It’s like most classically known for, or known as so. You got to remember though, it’s still a bond. It’s still a new, it’s not like you put composite in and all of a sudden. It’s enamel. You’ve still got a deep resin bond.

[Jaz]
The composite is still bonded to dentine. And that dentine may be more of questionable quality. In a more hostile environment, that’s more sub gingival.

[Alan]
Yeah, and so the question is why are we doing that? Okay. And the studies that are on it are very promising and it’s great and it works really, really well, but something we should remember from those studies is that these are done by very skilled clinicians to a very high standard.

So it’s like bonding the onlay, you can’t be sloppy with it. It’s got to be dry. It’s got to be isolated. It’s not like I said, squirt some composite in there and it just saves the day. And the reason we’re doing it is to make the isolation at the fit appointment easier, as well as maybe the scan and the impression.

And so sometimes I find myself looking at a scenario and most of the time. That’s going to tip the balance. Okay. I’m scanning this and isolating it for the fit are my preferences, but sometimes you look at it and you’re like, actually getting my matrix band or whatever down there, it’s going to be so difficult.

I actually think with some chord, I can get a good scan on this and I’m going to back myself to isolate that rather than, let’s say it’s like a mesial on a seven that you’ve got your clamp on and you just can’t get the band on there, that sort of thing. I might preferentially take the deep margin rather than elevating it. But most of the time, yeah, we’re going to elevate it with a bit of composite, reprep that margin to be our new finish point.

[Jaz]
It can be a lot of extra work, right? And so what I found, and I don’t know if you found this as well, is as over the years I’ve become more confident in my vertical preparation technique, which is the next chapter to discuss, I guess, in terms of when we decided we’re going to do a full crown, how often are you doing that shoulder and how often are you doing vertical technique?

That’d be an interesting one, actually. Let’s see if we align there as well. But I used to say a bit like 75, 80 percent enamel all the way around. Okay. I will consider an onlay as first choice. However, now I’m a bit stricter. Now I want 90 percent enamel all the way around and I want the width of the enamel to be not like a tiny line rim of enamel.

I want a nice band of enamel where possible, basically. And that’s going to sway me as well. But I am doing less and less deep margin elevation. So relying on that bond to dentine in a hostile, hostile environment, because when you can be so minimally invasive with vertical preparation technique, which is my full crown of choice more often than not, unless I’m replacing an existing horizontal crown.

Again, we’ll talk about this. If you’re thinking, what the hell is a horizontal crown kind of thing, we’ll come on to that. But I think that that’s been a big factor for me. So to summarize what Alan’s saying, if the aesthetics are going to be satisfied, if you can do gold standard isolation rubber dam, then and you’ve got enough enamel?

Totally. Overlay, onlay. But if any of those are struggling, then we may be going towards a full crown. Now, when you are doing a full crown, again, I was taught shoulders, right? Shoulders, chamfers, that kind of stuff. The amount of shoulders and chamfers I’m doing now when I’m doing a full crown is very few because by the time I’ve accepted that there’s not enough enamel, we’re too subgingival, there’s too much caries, there’s not enough structure.

The last thing I want to do to is actually put a shoulder on it. De novo, right? And so I’m pretty much like not a hundred percent. I’m nothing a hundred percent, but 95 percent of the time when I’ve decided that I can’t satisfy the criteria for an onlay and overlay here, because it’s not good enough.

The aesthetic situation is not good enough. The bonding situation, not good enough. The isolation is not good enough. I’m now going to consider a crown and that crown for me will be a vertical preparation. Can you now just comment on, is that also your thinking? And then before you explain onto a difference between horizontal and vertical.

[Alan]
Yeah. So the first thing you said there as well, just to come back to it was about the width of the enamel, as well as how much of it.

[Jaz]
The circumferential. So not about how much circumferential, how many degrees. So ideally 360 degrees enamel is great, but you might accept 320 degrees. But then if it’s 320 degrees of like a thin line of enamel, that sucks.

[Alan]
Yeah, for sure. But another way of looking at that same outcome is that the more tooth structure we’ve lost in height, the thinner that enamel is going to be, right? So the more we get down into the neck of the tooth, the thinner the enamel will be. And was it George Cardoso? You did a-

[Jaz]
Amazing. I was literally thinking of that paper he published. So guys, I’ll put this on the show notes. George Andre Cardoso, he did a brilliant little paper, really nice diagrams out there about decision making and how we go below the undercut, below the equator, above the equator. It’s a really fantastic guide that every general dentist, every prosthodontist should have. We’ll definitely include that. Great channel.

[Alan]
Yeah. So yeah, it’s fantastic paper. And yeah, so it came out end of last year and the sort of summary of what those guys were saying was that If less than a third of the tooth, basically they’re talking about the equator of the tooth. There’s like the tipping points.

It’s like three millimeters above the CEJ. If less than a third of the tooth is not more than the three millimeters height, so above the equator, basically like if you imagine, if you like de coronated a tooth right down at the CEJ. He’s saying, don’t do an onlay on that because you’re going to have that, not just the thin enamel, but you’re going to have such a height on the onlay that-

[Jaz]
It’s a really great term here. A vertical cantilever. So one of my American, Dr. Harpardeep, one of the Protruserati, she introduced me to that term, a vertical cantilever. It’s a really good way to think about it. It’s kind of like a crown to root ratio when it comes to like that kind of stuff, but on the crown itself, if it’s a really, thin height of tooth and a really long height of restoration, there’s a vertical cantilever, a lot of stress going down that cement.

[Alan]
Yeah, exactly that. So I think the two go hand in hand, vertical cantilever with less enamel width. So yeah, that’s a really good paper. Yeah. And there’s two parts to it. The second part is really good as well. So.

[Jaz]
So now we’re talking about, so we’ve just kind of discussed it in detail about, okay. Composite has got a limit. We’re going to be favoring onlays a lot of time because of how conservative you can be, and Alan and I have shared our guidelines as to when we think, okay, you know what, we’d like to do it onlay, but we can’t because it doesn’t satisfy some of those three criteria we talked about, enamel, isolation, aesthetics, and therefore we’re going to consider doing a crown. Now when it comes to a crown, a full crown, what percentage of the time are you, Alan, doing a traditional chamfer or a shoulder, and what percentage time are you doing a vertical preparation?

[Alan]
If you took out of the equation, replacing an old crown.

[Jaz]
Yes. So we’re talking about you’ve removed the MOD amalgam and you’re with that, you’re assessing the tooth for restorability and you want to go indirect, but you decided you can’t go onlay overlay. You’re going to be doing traditional cemented restoration. This is the point I want you to, this is the sort of split I want you to give.

[Alan]
I would say, if I’m honest, I’m trying to think the last time I did a horizontal.

[Jaz]
Me too!

[Alan]
Yeah, I recognize, I don’t know.

[Jaz]
Damn you!

[Alan]
Oh, I’ve got one, I’ve got one, I’ve got one.

[Jaz]
Okay, oh, thank goodness.

[Alan]
I did, but do you know what? It’s going to be less than a percent because I did the buccal vertical and I did the palatal horizontal because I needed space for a denture attachment, which I think is actually one of those ones. Cause most of the time people say, oh, when would you do a horizontal now, if you’re doing vertical, most of the time, and it’s usually for discoloration, right.

You need to prep in to get some things or even maybe you need to the teeth are misaligned, whatever, but yeah, one time I found myself doing it, I actually did a vertical on this canine and I looked at it, I was like, actually, they’re not going to fit the denture, like a little seating area onto that palatal. So I just did a little palatal margin. If I’m honest, I had to phone the lab afterwards and they were like, yeah, I don’t know what’s going on here. What have you done?

[Jaz]
I’ve done that once before by accident, inadvertently, like half a shoulder and half the tooth, a vertical preparation. It’s actually one of the failures I share in one of the webinars we did for VertiPreps.

But yeah, so to summarize guys, what me and Alan are doing, unfortunately, still very vanilla, still very much in agreement is when we’ve decided. That for that tooth, this is not replacing old crowns, by the way, right? Replacing old crowns might be different because you already have a shoulder chamfer there.

And if it’s a good chamfer shoulder, why make your life more difficult? Just go with the flow, just polish it up, right? But when we have that beat up tooth and we’re doing the restorative assessment and we’ve decided it’s not going to be an onlay overlay and we’re going to be doing a crown, a 360 degree crown, we’re more often than not going vertical.

And so Alan, what is a, because we all know chamfer shoulder. What is a vertical crown, even though we’ve covered in the podcast, but someone might be coming to this for the first time. And why are you favoring it so much compared to a shoulder chamfer? Why are you swaying away from the good old teachings of dental school?

[Alan]
Probably comes down to, I would say two main factors. One being like we talked about already tooth tissue loss. So like the biological cost to that tooth. And also it’s easier, like the actual prep is easier. And so it’s pretty rare, isn’t it? That you get something that is easier and better. That would be my two main preference.

[Jaz]
It’s better for the tooth, it’s easier for you. You don’t have to worry about rubber dam. Obviously when you get the foundation restoration, you got to isolate, but there’s no rubber dam and we’ll talk about the protocol stuff maybe another time, but yeah, it is definitely easier, quicker. I’ll tell you where I disagree in that.

When you’re learning the technique for the first few times, it’s such a flip. It’s such like a completely unconventional to what we’ve been taught, right? That you meet, you doubt yourself, you end up creating undercuts initially, you’re learning the learning curve initially, but once you’ve done a few and then you get some feedback from the lab and that kind of stuff, it can become very quick and to manage those dreaded sub gingival margins, it becomes an absolute dream.

[Alan]
Yeah. So the other thing you asked was, what is a vertical and, we say horizontal and vertical, what’s the difference here? So horizontal is that at exactly the type of prep we all know from university, where we are prepping horizontally into the tooth. And then the reason that it’s traditionally called a vertical prep is because you can, in the initial, so BOPT style preparation, the like traditional, where it started from was that the technician could finish the margin vertically, technically anywhere between the gingival margin and the base of the sulcus.

And it was a decision process of going subgingival enough that you don’t see the margin. But also not going all the way down to the base of the sulcus where you’re going to inch up the biological width. And so, but, yeah.

[Jaz]
If I was to summarize it to someone who’s never seen this before, I would say it’s not a knife edge, it’s not a feather edge, it’s kind of some nuances. But if you looked at a prep the first time, you’d think, oh, there’s a knife edge here.

[Alan]
Yeah, and then, but then that’s where the confusion came in of the shoulderless, so the butt bur technique. Cause it does have a margin, but it’s not really a margin. It’s just a change in contour. It’s a change in the direction of the tooth. But if you looked at it, you could say there’s a knife edge there. Even though you haven’t got your bur and created a margin.

[Jaz]
You know what that reminded me of? Attiq Rahman, who we all know and love. He teaches on his veneer course. I only know cause I speak to friends and they tell me I’ve had great things about Attiq.

Never been on his course, but we liaise on Facebook. Really top guy, really great educator. And when you’re talking about, the prep for a veneer. And when you’re doing the cervical, the gingival area of the upper center incisor, for example, right? The enamel there is so thin, classically 0. 3 millimeters that you really want to be minimally invasive.

And so what he doesn’t like the term is margin. He doesn’t like the term chamfer shoulder or anything like that. For the label of that, he describes it as a change in texture. So when the lab see on a model, they see that, okay, this is the root. Oh, and then suddenly there’s a few little bur scratches here.

It’s a very subtle change in texture. And I think that’s a great way to translate it into vertical preparations that a technician gets it. They see the, imagine they could see the whole root, see the whole root. And suddenly there’s a change in angulation, change in a deflection, there’s a change in texture.

And that then becomes our margin or doesn’t even have to be there. It can be somewhere near there can be where the technician finishes the crown.

[Alan]
Yeah, I like that. Yeah. And that’s that definition, isn’t it? And that’s the differing protocol between edgeless and shoulderless vertical preparations. And I think for me going into vertical preparation then that was where I kind of, it took me a bit more time to align those two processes.

It’s a little bit like I was saying before, the vast differences between PFM and onlay, like, Oh, which one do I do? They’re so different. Whereas then BOPT and butt bur, which are edgeless and shoulderless, they’re so different as well. And if you only have one of those in your arsenal. Then you might find, say you only ever did BOPT, you’d be like, Oh, there’s a lot of bleeding with this vertical stuff, isn’t there? And it’s pretty disruptive.

[Jaz]
BOPT is definitely more challenging. It doesn’t lend itself to immediate impression, immediate scanning, that kind of stuff. So now I mean, this is for the really geeky ones. If you’re doing vertical preparations and which you are on the molars and premolars and stuff. So let’s say you’re doing full crown. You decide it’s going to be a vertical preparation. What percentage of the time is Alan doing? Shoulders are not on anteriors, cause the game changes anteriors.

On posterior teeth, what percentage of the time are you doing shouldness? What percentage of the time are you doing BOPT, which is going a little bit more sub gingival, a little bit more invasive if you like, but for good reason, try and grab more ferrule or change the aesthetics a bit more.

You prep further into tooth for whatever reason, which probably is beyond the scope of this episode. How has your split look like?

[Alan]
I would say 90% shoulderless.

[Jaz]
Okay. Yeah, yeah, same. I’m probably 95, 98 percent shoulderless.

[Alan]
Yeah, yeah. Oh yeah, I would say 95, really. I was trying to think of one.

[Jaz]
I was hoping you’d go the other way. Just a little bit, just a little bit, leave way. We’re like, it sounds like bloody twins here, man.

[Alan]
But, okay, here’s, this is a little bit different. So one of the other things that we teach is like this little blend of the two. So for example, a bit like what I was saying with that canine I prepped where I needed to prep a horizontal on the palatal.

What we’ll quite often do is do, prep the whole thing with a bapper, place our cord and then take the flame bur. This was something Colin McGuirk showed me as well. Take the flame bur and just take that little change in contour off on the buccal. So you’ve effectively got an edgeless on the buccal.

So you can hide that margin a little bit, but you’ve been super conservative on the other three sides of the tooth. It’s just a nice way, especially on fours and whatever. And it stops that, like I said a minute ago, that like mindset of, Oh my gosh, am I going full deep to the bone, BOPT, or am I doing this shoulderless, how do I make sure I’ve got no undercuts?

And am I going to end up equigingival or even slight supragingival if I’m not careful? So yeah, we teach this like nice little blend of the tooth and it gives you best of both and it stops it being too aggressive, basically.

[Jaz]
I like that. It gives you a bit more space in that area where there might be some discoloration. It allows you potentially to grab a bit more ferrule there as well, right? But you’re still being very minimally invasive. And you can, not that you would on a premolar so much, but if you wanted to then maybe play about a little bit with the gingival level there. You could, but that’s more in the anterior world.

Alan, I think we’ve covered quite extensively, but I think, unfortunately, we’ve agreed to everything, damn it. Is there anything else that you wanted to add in terms of what we’ve discussed before? I want you to tell us about where we can learn more from you, but before we get that, any reflection points based on our hour long chat so far?

[Alan]
I’ve got one question for you that might get us off being completely vanilla.

[Jaz]
Please, please, please, please, please.

[Alan]
Do you place a seating groove in the middle of your occlusal on a prep?

[Jaz]
I do. If I’ve got composite, so if I’ve got composite there, but like a large composite core or an endodontic access restoration, I will get the big Burtha bur and sink it in halfway to make a nice little notch, which helps the indexing seating for the technician on the model. I don’t know if it really gives you a lot more resistance form, but I wouldn’t do that if I had to sacrifice dentine for it.

[Alan]
Yeah, I don’t do that.

[Jaz]
Thank goodness.

[Alan]
Yeah, I don’t do that. I pretty much, I rely on my bevel to give me my seating position. And my worry with it is that like the more, it’s not a retention groove, but sometimes you see these preps where it’s like, Oh, I was a bit worried about how well this was going to bond. So I added in like a little retentive box or something and you go, okay, we need to pick what we’re doing here. Are we relying on adhesive dentistry or are we going to use some more retentive elements? Because if you start blending the two, any overlap is going to counteract some of the principles of the other.

So for example, anything that’s not smooth and flowing on an bonded restoration, you’re going to be creating internal tensile stress, anything that is not a sharp change in angulation. And so my worry is, and the other thing that my colleague Ollie Bailey always says is that ceramic fractures from the inside out, that it fractures from those internal changes in direction on the prep.

[Jaz]
Stress points.

[Alan]
100%. Yeah. And then it cracks on the inside and comes out. And so you want to do everything to avoid that. And the other thing that he says that he always brings this up on the course now, and you kind of alluded towards it earlier. And I think it really is a nice thing. Nice way of thinking about it is that when we’re talking about onlays. You said you had that worry of like cusp reduction and people underdo and that is a less critical area of the tooth in maintenance.

[Jaz]
And the longevity and the success of that tooth is not dictated by how much occlusal clearance you do is dictated by that gingival third.

[Alan]
Yeah. It’s all about the percervical dentine. And the way he says it is that if you’re going to chop down a tree, you don’t start snapping branches off from the top. You go straight in at the base with, with your axe and it’s the same with the tooth. Those little bits of cusp.

[Jaz]
I love that. I love that. If anyone was multitasking, that was just brilliant, right? You need to go back and listen to that again. If you missed that was golden. I love that.

[Alan]
That is an Ollie Bailey classic.

[Jaz]
Well done, Ollie. I’ve got to get Ollie on the show, man. I’ve got to get Ollie on the show. I’m going to do it. This is the spark to talk about trees and, okay, brilliant. I’ll get Ollie on the show as well.

[Alan]
Oh, mate.

[Jaz]
I bet he’s like an encyclopedia.

[Alan]
Do you know what? It’s a blessing and a curse because someone asks a question and when you’re on the course, you’re at the front. You say something, you think, I think that’s the answer. And he’ll go, yeah, there was a systematic review on that. Well, most of the time so far. He’s backed up what I’ve said with some literature.

[Jaz]
But with evidence.

[Alan]
Exactly. And I’m like, yeah, I think I heard that too.

[Jaz]
Everyone needs an Ollie in their life.

[Alan]
Yeah. Last Chris saw that.

[Jaz]
Tell us about your teaching, my friend, because I’m a big fan of promoting Protruserati like you. There’s so many courses out there. So many questions to learn from, but everyone will learn better from a different type of educator. And what I see, all the good stuff you put on the social media, I can see that you’re such a reflective practitioner. People rave about your courses. Please tell us how we can learn about your prep courses.

I would love for the Protruserati to come and join you and learn from you. For those who find that they’ve really enjoyed your episodes.

[Alan]
Yeah. Thank you, mate. I mean, so, I mean, it all started with a composite course that myself, Ollie Bailey and Chris O’Connor started about, probably coming to three years ago now. Yeah, got it started and it was a case of see how it goes. And it kind of snowboard when a bit crazy, very crazy, really kind of was selling out quite far in advance. And so what a lot of the feedback we were getting was, we’d be really interested if you guys did some sort of prep course as well, because you know, those things go hand in hand, don’t they?

You find the same people want to learn those things. And so composite course was very much like a touring course. So we set it up with the intention that we could take it anywhere. And we designed all the practicals so that when you go on a course and like everyone drills a class 2 but everyone’s drilled a different one and then you’ve got to try and solve different problems, everything is like structured so that we can problem solve it all together and get the same outcomes, but we can tour that course.

So we do that in Newcastle, London, Bath, and we have done it in Manchester. And so then when we got asked to do this prep course. We’re really keen to do it and we wanted to sort of give it everything, but we thought it was really critical to have phantom heads and, and water flow and we want to get as realistic as possible.

And so, like any good idea, we came up with this sort of building a phantom head and a training center. And Chris and the guys at Incidental took that at the helm and went for it. It’s like any good idea ended up being a way bigger project than we perhaps anticipated.

[Jaz]
I know how hard he worked basically to set it all up. So yeah, behind the scenes what happens is absolutely crazy. I’ve seen that.

[Alan]
Yeah. He put his heart and soul into it, but yes, paid off. We’ve got this fantastic training center up in Newcastle and it’s been great. I think we’ve run the prep course six times now, by the time this goes out, it’d be significantly more than that.

And it’s been really nice to see a lot of the same faces from the composite course. But also what we didn’t expect is we’ve had quite a few people come onto the prep course and then go, Oh, this is kind of a nice way of teaching, maybe I should do the composite course, and so on. So yeah, it’s been great.

And I thought initially, Newcastle is quite far North, but then Cornwall is quite far South. But actually I found, unless you’re coming from Cornwall, it’s pretty easy to get to, that I think was the most stumbling block. The math, you know, it takes way longer to get from Cornwall to London than it does London to Newcastle.

It’s like, wow, it’s way further to get to Newcastle. But I think the train from London is like just over three hours. It’s mad, it’s easy. It’s really convenient. So yeah, it’s been nice going, going up there. And-

[Jaz]
Well, if you want to learn from three educators, right? You, Ollie.

[Alan]
Sorry. Yeah. So, so sorry. It’s me, Ollie and Chris did the composite course and then we brought Colin McGuirk on board for the prep course and him and I have been teaching together for quite a few years. They know each other from uni.

[Jaz]
He’s a really in incredible, he’s guys really humble. I love humility. It’s a great character. And so, if you are in that neck of the woods or even not come international, come and check the good British course out, right? We’re changing the scene when it comes to British education. So support local, and I would love for you guys to support, his prep course, if that’s part of your PDP this year. What’s the website for that buddy?

[Alan]
So you can get all of that on through the Incidental website, Incidental Limited, and just click on the training courses link.

[Jaz]
I’ll put that in the show notes and your Instagram handle.

[Alan]
It’s the Cornish Dentist.

[Jaz]
Amazing.

[Alan]
Yeah. Most of my stuff, put up there and like you said, try and chat about cases and whatever, and, break it all down. Like it’s not a before and after page. It’s not really for patients. It’s just for dentists and see how things go. Now, like we said, about coming from anywhere for courses, I think the biggest compliment we ever had, we’ve had two people who didn’t know each other on separate courses, that flew over from Canada for the course.

We’re just blown away. We’re like, hang on. So you got family over here or you’re staying for a week or two? They’re like, no, just here for the course.

[Jaz]
I can just imagine someone, right. Having the photo of big Ben and then looking up and seeing Newcastle.

[Alan]
Oh yeah. No, but it’s like, yeah. Ultimate compliment really.

[Jaz]
That is amazing. And well deserved. Lots of Canadian Protruserati, so do consider it if you’re from that side of the pond as well. Alan, thank you so much for sharing so much goodness. As always, I’ve had such a great time talking to you. It’s such a great darn shame that we agree with everything, but it’s nice that you don’t do those big Burtha notches and I do. So let’s take that as a small win in that regard. And I’m sure we’ll catch you again on a different topic that we’ll love to just break down.

[Alan]
Awesome. Thanks so much for having me, mate.

[Jaz]
Well, there we have it, guys. Thank you so much for staying all the way to the end like you always do. Do you remember what percentage of tooth structure is removed with a vertical preparation according to the study that Alan mentioned?

Do you remember what it was? Because that’s one of the questions you need to answer to get CPD. If you get 80 percent of the quiz, you get your CPD certificate, verifiable email to you by our CPD Queen Mari. You also get, like, quarterly certificates and annual certificates. Making protrusive guidance the best value educational subscription there is.

For weekly certificates, like if you’re always listening or watching the episodes all the way to the end, then you’ll definitely get your money’s worth. You’ve also got access to all the different masterclasses we have on from Sectioning School to VertiPreps for Plonkers. That’s on there as well. Lots of dentists have already seen the entire course and started to implement it so they can now offer vertical preparations to their patients.

Remember, the goal of VertiPrep for Plonkers is to get you to place your first ever vertical crown on a premolar tooth. Check out protrusive. app if you’re interested in that. If you found this episode helpful, please, could you share it with a colleague? That really helps us to grow. And of course, wherever you’re listening, Apple, podcast, YouTube, please hit that subscribe button.

Thanks so much. And I’ll catch you same time, same place next week. Bye for now.