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Bookmark The Inlay, Onlay and Crownlay Preparation

Dr. Wally Renne explains in detail why we are not doing enough inlay, onlay and crownlay preps, and how to use these prep options to create stronger more beautiful restorations.


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Video Transcript

You’re not doing enough onlays. You’re doing too many composites. Promise you.

Let's go to the research. You're not alone only 4% of dentists do inlays and onlays - only 4%. I think they're better restoration than anything else is out there in existence. You preserve enamel when you do an inlay or onlay. We know that if you do, you preserve enamel. The dental bond is going to be protected. That enamel is going to be the gatekeeper to that dental bond so it's going to help that restoration last longer because we know if you don't and you have a margin down on dentin, the bond strength is going to decrease 40% in 6-12 months.

So we want longevity to these restorations, we want gold-quality longevity. When we transition from the era of doing gold to the era of PFMs we lost all ability to be conservative Dentistry. I feel Because with gold we used to do all these fancy inlays and onlays and they lasted forever. I have patients that have 30 to 40-year-old restorations.

We can do the same thing with ceramic, we can even be more conservative than they were with gold because we don’t need mechanical retention, sharp point angles, and line angles. Let’s look at this class II longevity 11 years for amalgam and 6-8 years for composite. It’s definitely true in my hand and I’m not talking about these. I'm not talking these super little - about a patient of mine a teenager - do the little composites on him - those are probably fine but I’m not talking about that. I'm talking about the bread and butter composites the bigger, the deeper things that we're doing on daily basis. Those composites are fine but if you look at research it’s the giant composites that suck. Probably a disservice to your patient. 50% fail rate at 7 years for bigger composites versus amalgams only had 20%.

7-year longevity on this one study was a randomized controlled clinical trial on real people on real patients followed for 7 years composites just were terrible. These were all placed in a rubber dam using excellent material. It wasn’t a materials problem. Gordon Christensen says the average longevity of a composite is six years.

That’s what I tell my patients. With a patient that you have a bunch of composites on, you can do these composites they’ll last about six years, you’ll be back, we’ll replace them and the hole will get bigger every time you re-do it. They usually say “Doc, I don’t want to see you ever again.” Well, we can do something that will last twice as long. We can do an inlay or an onlay. It might cost you twice as much, but you don’t have to come back. I do more of those anything else.

The research just confirms it over and over again that direct resins, maybe are not what we thought they were. I mean we have patients that come from all around the country to this school. Maybe I'm only seen my work that keeps showing up.

Two and a half years old - bombed out. Any endodontist in the world will tell you they’ve been so busy since composites got really popular. I know none of y'all have these problems but I do. My composites aren’t the best in the world. Half of these pictures [from the slideshow] are mine half are from somebody else but what's going on? We all have a machine that could do way better for your patients.

Gordon says that the in-office milled restoration is the gold restoration of today. He says that onlays are an acceptable and desirable crown competitor. They have a 90% success rate at 10 years. Research, after research, after clinical research shows that these are super awesome restorations for patients yet we seem to go from composite to crown.

We got two options a giant composite that will cost you $350 bucks or use a crown that will cost you $100 bucks. But there is a middle road that more people are jumping to and they talk about it more.

The inlay is not profitable to you unless you do it fast. I understand why everybody’s not doing inlays it’s a money loss problem. Patients don't understand “I got this small thing, why can’t you just slap some composite in there?” This is it perfectly fine, I understand but if you mill it out of resin you can do it an hour. Hand-polished and seated in an hour, once you get fast and good and you can charge two or three some cases four times as much as a direct resin. It depends on what you're comfortable with and where you are in the country, but if you look at the research why then would a milled resin do better than a direct resin?

Well, the studies show and this is a recent study, 2015, using the best newest composites out there in the market the best direct resins they still suck.

Here’s what's happening. They still flex at incredible rates and stress out the bond on the tooth dramatically compared to an indirect milled resin.

So if you look at the stress that’s put on the restoration here we have and this is the stress on the tooth. Here we have a milled resin seated into this tooth and look at that red spot is the only stress that’s put on the tooth on loading. Here’s a direct resin you're stressing out this whole tooth the bond on the tooth is flexing a dramatic rate you're going to rip that restoration out it's going to leak and they are going to have issues.

And the studies to confirm this. Look at the higher bars for stress put on the restoration and the tooth interface. So the stress values are 8 to 14 times higher in a direct restoration than an inlay. So the fact of the matter is even though you're milling resins and delivering a resin indirectly, it’s way better than a direct resin. So don't get in your mind “Oh, I’m just milling composite on a stick”. It's not the same thing. It’s way better, way better for your patients.

So here we go we have a patient with an amalgam. They have a crack on that mesial margin ridge. You’re [going to do] an amalgam prep in reverse. So you’re just got to take everything out and then make a trawl.

I would hate to do a composite there put a ring, like $50 in rings and sectional matrices and wedges and isolation and all that kind of stuff.

Just mill it, hand polish it really quick. We’re going to show you tomorrow how to use the die shine. It's the fastest way to polish. It puts a high luster on Lava Ultimate, which is a good restoration for inlays and onlays, not full coverage crown. You're going to deliver that restoration hopefully within an hour period. So you can still be semi-profitable.

Here’s another one you have this giant composite. This is inlay territory. Take that out.

I show rubber dams because I lecture and if I don't then everybody in the audience raises their hand says I didn't do good dentistry but you can do without rubber dam. I guess I don't know. People do it all the time and it works well. Isolite is probably even better.

Okay so marking your margins, bonding... Here you have a bonded [restoration]. They don't win any awards for aesthetics. You're not going to customize them and you're not going to stain them. Just polish them and get them in the mouth. They are a functional restoration. You need to be profitable. You can’t be tinkering with stains and groves. That’s lecture stuff. No one is going to do that for an inlay in the real world unless they schedule like 5 hours or something.

So here we go look at this tooth, giant composite, decay here and a fracture going across the pulpal floor... and so this patient symptomatic, with cracked tooth syndrome. Hurts upon pressure upon biting releasing the pressure. You would never think inlay in your life for this you would think endo, full covered crown or full coverage crown or something like that right? You would not be gearing towards the inlay because you would be worried about crack, having cracked tooth issues right?

So how many people here would do [a] crown? Anybody would take it out and put in an amalgam composite? Another bigger composite?

The onlay - this restoration makes a lot more sense than the inlay - because now you're in crown territory or a very difficult composite territory nobody wants to be tinkering around with composites on this and you know that it's not going to be a good restoration for your patient long-term.

So now you're torn between do I slap some putty in here and call it a restoration with some plastic or do I mill something more conservative than a crown and preserve what's remaining? This is the best restoration you can do for your patients. It is also the fastest and most profitable. When you're not having to spend time to spin down the rest of the tooth and you can just remove what's defective real quickly and mill something that fits in that space, time savings on prep alone is significant. Your margins are kept higher less packing of cord, less issues with isolation.

Let's talk about this real quick so how do you design these because 90% of these are going to come in with a giant MOD amalgam and a cusp broke off. MOD amalgam floating in air and a cusp popped off or MOD amalgam and a cusp undermined weak and it has a crack, something like that. Marginal ridge is cracked, maybe an MOD amalgam and a cracked marginal ridge stuff like that and you’re just suspicious.

Well if you look at the research how much do you cover? When do you need to cover? The more conservative you can be the better. So if you got a cusp that you want to overlay, the palatal onlay, for example, MOD amalgam was sitting here the palatal cuspid was weak so just shoe that one cusp. You don't need to go on to the non-functional cusp unless you think it's super thin. What’s thin? Less than 3mm. If it’s less than 3 millimeters, you should cover it. That would be called the occlusal onlay and what I mean by cover it is you're just going to cover it you're not going to prep it down at the cervical. You're just taking off 1 1/2 to 1 mm off the cusp and laying that inlay or onlay onto that tooth. If you want to make more of a vertical stop, it's up to you. If you want to put a little tiny finish line on the facial it’s up to you.

This is the worst option. When you want to protect the cusp when you think you're doing good you prep it down and go all the way to the tissue with the prep. You’re not really protecting that cusp like you might think. We’re going to talk about that. These are the different styles. This is the worst. These two are pretty much the same.

What you want to cover both cusps and just get it over with. If you cover all the cusps on the tooth the ADA code is a crown. In my opinion, I don't know how you guys feel but if you're covering all the cusps on the tooth - it’s a crown... This is ethical, I understand cause insurances don’t like to pay for onlays that are less expensive but if you want to do a crown but you want to help save some tooth structure, cover both cusps conservatively, use your same code that you know everybody gets reimbursed for but you could maybe sleep better or just feel better that this prep takes one minute to do, you're not shaving down unnecessarily all this healthy remaining cusp and the clinical studies show that you don't need to go down and put a margin down there at the tissue.

So if you look at the research you know even these ultra-thin ones are holding up better than if you did a 1.5 mm reduction with eMax. All this research is predicated on eMax usage. The inlay with the resin, we're not doing. I'm not doing the resins with onlays. I’m using eMax. I built my practice on eMax.

Look at this, this is one where they went down to the tissue - we're getting weaker fracture loads all across the board here especially when your being conservative and you're trying to be thin down there. That's the one I like to do. I’m torn between .5 and 1 mm

Okay that's good but what if I want to save some cusp, how do I know what cusps to save? Well, it depends on how the patients functioning. Always save a cusp that’s under compression. Cover the cusps that are under tension with occlusal forces maximum intercuspation and excursive either or. Let me show you what I mean by that. Taken from Dr Milicitchm who is a leader in the biomemetic world of Dentistry. These cusps, where these marks, are these cusps being pushed towards the center of the tooth or they be pushed off? What would you say? They are being pushed towards the center - save it. What about right here? Is that cusp being pushed off the tooth? How about this one? Cover it.

Another alternative is you could do something called a bear hug. A bear hug is what I call it. If you have a cusp at under a little bit of tension but it’s super thick and you want to save it, wrap your margin around a little bit, to kind of protect it so you can imagine the bonded restoration on there, wrapping around this corner here. If that cusp is under tension it's going to actually hug that cusp and protect it from falling off the tooth. Does that make sense?

It’s easy to do it’s like a quick little margin. Here’s him showing it here, you see how he does that, it wraps around a little bit with a little bit of a margin and this is how I do it. We have a cusp here that's under tension I want to save it. Actually, I’m going to get rid of that cusp probably so I’m covering that cusp but this cusp was under tension also but I want to save it because it was a lot thicker. I put that little margin around it to kind of protect it. So that's the design. That's the design restoration there. See the anatomy that you could add. Tere is the Emax onlay. I recommend HT most of the time for onlays for eMax but go one shade brighter than you pick. So if the patient is an A2 use an A1 HT.

Here's another case, look at this giant composite. Where are those forces on this case? Compression here, tension here. Wanting to pop that cusp off and in fact it has a crack on this marginal ridge here. I’m going to take that cusp off. I’m going to cover that cusp. These cusps I’m going to save, even with that amalgam there. Watch, took the amalgam out and put a composite. This is easy to do.

There's the HT eMax blending in. I'm not spending a lot of time putting stains. I’m trying to get the patient out the door.

Another one, in this preparation - what about that crack? Everybody always raises their hand, It’s going to propagate to the brain, the patient’s going to die. No, it’s not. Look at all this enamel around here. We know that when you restore that tooth - the crack, everybody has cracks in their teeth whether or not they are symptomatic is your number one concern. Are they symptomatic? Then maybe you address it. If they are not symptomatic, I don’t worry about them. It's kind of a gray area so maybe you don't want to do that your practice but I haven't had issues. If I cover them and I bond them with a rigid glass material.

That’s the key there is the rigid glass material. You can’t use composite materials, You can't use the Lava Ultimate or Enamic, even on those. You really want to have a rigid ceramic so it's splints the tooth together. So, eMax is really the ideal material for that.


The last thing I’m going to talk about is the crownlay. This is definitely ADA acceptable as a crown code. It’s much faster to prep. Your saving 70% of the tooth structure compared to a conventional crown. So it’s a no-brainer.

So normally you're going to put your margin at the tissue, right here. We know from anatomy and just from common sense that the nerve ... doesn't live up here. It's pretty close down here at [the] margin. Let’s say the patient has a little recession. So now you’re down a root. You’re having to reduce so much tooth to get a path to draw above. You're taking away a ton of enamel up here to get your little margin down here and there at the tissue level. You’re going to heat up that nerve that's why about 15% of regular full coverage crown preps require endo so if you like doing endo, I don't recommend changing to this prep technique but that's what you're looking at - not all the time but sometimes.

I don't know why you need to do that. Was there something wrong with the buccal cusp? Did it make you mad? Did you need to cover it like that? I don't know. There are better ways to do it.

Let’s look at this 3D animation. This is a regular 1 mm chamfer or shoulder preparation here, ghosting over with 6 to 10 degrees of taper over this root surface. We're going to just ghost over the nerve right now and you can see barely but you can kind of see how the preparation is near the vicinity of the nerve. You’re not going to hit the nerve ... but all that friction and trauma could send that tooth to endo, that maybe didn't need to go to endo.

I havent had to cut a hole through a CAD/CAM crown to do Endo in five years since I've been doing crownlays. We used to do them all the time with gold. Then something happened we stop using gold we said “We just need to cover everything at the level that issue no matter what.” Right down there.

Go back to these more conservative days with your ceramic look at the difference - regular - crownlay. Usually, these are coming in with a giant MOD amalgam and weakened cusps. You’re going to cover all the cusps of the tooth.

This is what you’re going to do different. This preparation is faster to do because you’re not reducing as much. You’re not going near the tissue that you're keeping your buccal and lingual margins at the height of contour, at the most fat part of the tooth. .51 mm shoulder depending on what you want to do. You’re still reducing all your cusps down you have a gentle slope to the proximal contact area. You’ve taken out that amalgam. It's not a box. It's a gentle slope. You don't want box forms. You're just ramping from super high to super low. You have a V-shaped central groove area, rounded cusp tips. You don’t want anything sharp with all ceramic.

I do more of these then I do anything else in my practice. Bonded on eMax, can kept 1 mm thick or more, depending on your comfort level. I hover right around 1 to 1.5 and that's what it looks like on the lingual. See how is high all that thick band of enamel and then you're ramping down always break proximal contact. I don't care what you're doing but it's just a ramp down there it's not the sharp drop off because it doesn't mill well to boxes. This is why inlays are so hard to do.

But this is direct from Ivoclar. They call it an occlusal veneer in Europe. Southeast call it a crownlay. Other areas of the country called different things but the fundamental principles are the same.

This is from Ivoclar recommended material thickness for eMax for these types of restorations. So it's not from me saying that you need one. It's from them which means you can pretty much take home that it's going to work. It’s strong. They do a lot of research to ensure they're not giving you misinformation on how to reduce for their materials but that’s is exactly the way I've been reducing.

Look at the nerves way down here. We’re not putting margins below the tissue or we’re not doing anything like that. This is so conservative. It’s what I would want.

So for depth cuts, I like to use either Meisinger depth cut burs or the Brasseler depth cut burs that they came out for eMax. But the 1mm for the crownlay. They just bottom out. They’re idiot-proof just kind of stick them in and make some stripes. You can't overdo, because they just bottom out at this hub.

So let's look at what these look like clinically if you're looking at them top down it looks just like a crown. Like if I took a picture of that that's that's a crown but if you look at it from the side that's not a crown. That’s something ... we would never put margins there is we are doing a PFM or something right but look at what happens to the margins when you use a high translucency glass. Can you see it? It’s there somewhere and you're not going to get that every time.

The patients never complain about a margin on a crownlay restoration, even on a first premolar, that I've kept height of contour. They never said “Oh what’s that transition?” You know if the patient has like a black tooth you're trying to hide it obviously you're going to go down like a regular crown and cover the whole tooth. But I’m talking about the instances where you can do something more conservative or where you have no choice. Like here, I had no choice but to do a crownlay.

Giant MOD amalgams, decay underneath - if I prepped this down for regular crown I would lose this whole cusp, these cusps. I would have a flat table top nothing but if you're more conservative you be surprised how the tooth transforms into a tooth that actually has some tooth structure left. If I were to spin this down at the level of the tissue I would have lost the buccal and lingual cusps.

These are those restorations delivered. The margins blend in fair enough.

We do time and time again we got too many of these to say it doesn't work. We definitely passed the 5-year mark on these. We're at the seven to eight year mark with a lot of these. Some of them blend in better than others. That's a little bright but you get the idea.

This the last little video, I don't want to insult you by showing you a typing on video but I’m not cool like Alex I don't have a film studio in my office, he’s got all that fancy equipment.

These preps are the fastest preps to do. Get your depth cut bur. In this case it’s a 1.5. You’re just going to kind of mindlessly sink it into the tooth. You can make potholes, you can make stripes. I can't have water on for the purpose of the video or else it gets all over the camera.

I like to go into my buccal and lingual grooves with it. I think it’s either a 1 or 1.5. You’re just going to smooth out your depth cuts to add more on your cusps up your transverse ridges if you want. That looks like a final prep check for Freshman dental student.

This is a Mac bur. Because it’s fast and cuts you have to be careful with this thing. The bigger the bur the faster it cuts. That thing will cut the occlusal, it'll cut so fast you don't want to give this to a student, but yet we do.

It’s a 35 round bur.

If you want speed and efficiency, it makes a football diamond looks like a princess toy.

We got that occlusal, we smooth out our depth cuts. You can go back with the football diamond if you want to and accentuate anatomy but you really don't need to. You don't need to do this step that's just me playing games for the students.

[Inaudible question]

If you wanted deep, deep grooves on your design without getting those thin spots that’s when you [do that] depends on how crazy you want to get with your anatomy.

So that's the basic occlusal reduction. Super easy, super fast.

We're going to do interproximal reduction. I don't like to take steps and use a thinner diamond but you certainly can if you're not comfortable. I go ahead to the 847KR18 that I showed you and usually there’s already an amalgam there. Why would you be doing this if there wasn't? So it's already done for you. You're going to take out that amalgam … So that box it pretty much already there. So you’re just removing that old amalgam and you stop at the level of where the amalgam stopped, unless there’s decay, you clean that up ... so that's the thing you’re just kind of going through there but like I said ... it's important to visualize this tooth that had a giant amalgam.

What you're left with is these sharp, deep boxes so now how are you going to transition from these deep tissue level boxes to a margin that's at the height of contour of the tooth?

So what I like to do is first do my height of contour margin before I make that transition. Now I'm going to just ramp it down into that box. The way I think about it is if you're a small little dude in a wheelchair or if you're train going around train track and you're going and you come in this corner, if it's steep, the restoration is not going to fit well. In my experience. A slow gentle slope down to that box. You get such a nice fit. Nothing I hate more than looking down everything fits good and have a little corner down in the box that’s open. It’s unacceptable.

By prepping things smooth and round you could avoid that for sure. So now we're just adding the facial. The facial is kept roughly at the height of contour of the tooth. Even if they have an abfraction lesion down here, like Alex showed, leave it alone. Do you know how abfraction lesions if you’re trying to incorporate that into you prep, that you then have to reduce so much more to get the abfraction margin and all that stuff?

These are separate and distinct parts of the tooth it’s like you going to get heart surgery and they work on your toe. In the tooth realm that's a separate and distinct.

So that's basically all there is to it and then we're just going to round off some of the sharp peaks on those cusps and that's it. So it's a really simple straightforward preparation. One I think it is completely underutilized in the dental world. Europe - they do a lot of these more conservative, biomemetic type preparations like these are pretty popular with bonded eMax and lithium disilicate glasses and stuff like that. You’ll have a chunk of enamel in the facial and lingual.

You don't have to worry about cusp popping off. You know “Did I cover it or not well?” “Should I have covered that cusp?” You don’t have to worry. It's ADA coded as a crown. It’s fast and easy to scan. At hygiene recalls you can check those margins. A patient could brush those margins. Super easy.

So I’m just going to show you one quick case with it and then we're I think we're done. This is a patient, an emergency patient. A lot of these are emergencies. Big composite, in this instance a broken cusp … This is the crownlay prep - from the top it looks like a crown prep. You can’t tell the difference.

This is real-time scanning with a portrait tip. This is about how fast you guys should be. A portrait tip is a faster tip in my opinion.

We’re at the height of contour on the lingual. That’s cord down there that will ripple down there. That's not the margin. It’s just some cord. Get into this corner. I’m holding this tip and I’m holding the yaw of the tip to shine into that. It's going to scan lock and not let me over scan that corner but this is a 5-6 version software.

So I got a bunch of crap. I got a cotton roll here. I just took a took a quick glimpse at my model before rendering it. I decide I need to get a little more. I didn't render and check, I just looked at it without rendering and said I need to get that molar and a in a little bit more in this corner right here.

So that's at the final impression. That wasn't glamorized. It wasn't cut short it just kind of what I did while filming it. You should be at that time. I'm erasing whatever that was I scanned. It was either cheek or something. Here’s the model rendered. I lost my margin right here because I suck. I didn't get enough retraction but I'm going to try to pick it up in ICE view.

Opposing should be lightning fast. You should not spend more than 15 to 20 seconds on your opposing. That's your opposing and that's everything that you need.

Your bite should be just as fast. Your prep final impression should be the longest scan you're doing. So here's my bite scan. There we go. I'm working my margin. I'm tinkering around with this corner, right here, in ICE view. Turn off auto-genesis. Checking my margin, auto-genesis turned off. Position my crown. it designed it and now I’m just stretching it out. I’m going to show you how I like to do this I think in a little bit. I like the slick anatomy I'm all about Anatomy. These are thin, remember? 1 mm. So it’s about 1 mm thick 1 to 1.5.

There it is delivered. There’s the xRay of it. That’s the fit you should be getting. That’s with Nexus 3 cement.

Walter Renne

Submitted on
October 13, 2015
Last updated
March 14, 2019
Total views

About The Presenter

Dr. Walter Renne graduated from the College of Charleston in 2003 and went on to graduate from the Medical University of South Carolina (MUSC) College of Dental Medicine in 2008. He is an Associate Professor and the Assistant Dean of Innovation and Digital Dentistry at the MUSC College of Dental Medicine and is active in undergraduate dental education – holding a full-time faculty position in the Department of Oral Rehabilitation at MUSC.

Dr. Renne is the director for CAD/CAM technologies and runs the CAD/CAM and Aesthetic clinic at MUSC. He has been instrumental in integrating E4D Compare computerized assessment software into the curriculum, where it’s a critical component in Dental Morphology and Fixed Prosthodontic I, II, and II.

A leader in the field of digital dentistry, Dr. Renne maintains an active general dentistry practice that utilizes both the CEREC Omnicam and E4D Planscan systems. His special interests in patient treatment include advances in CAD/CAM dentistry, adhesive dentistry, and conservative dentistry.

He is active in dental research and currently has a patent for a new dental adhesive that is permanently antimicrobial, in addition to having revolutionary bond durability components that prevent enzyme degradation of the hybrid layer – which may prevent recurrent caries and bond breakdown in the long term.


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