Zirconia Crowns vs Lithium Disilicate Crowns: Clinical Applications and Delivery Methods

You're listening to the Phil Klein Dental Podcast. So if you're a dentist and you're putting in indirect restorations, you are faced with the question, what material should I use? And usually the contest is between lithium disilicate and zirconia. And once you pick a material, then you got to decide, do I bond it in or do I use a traditional looting cement? To give us his perspective on this is our guest, Dr. Todd Snyder. Dr. Snyder is a popular speaker on VivaLearning.com, a cosmetic dentist, international author, lecturer, and consultant to dental companies. He hosts a weekly podcast, Delusional, winning the weekly war of dentistry. You can reach Dr. Snyder at legion.dentist. Dr. Snyder, it's a pleasure to have you back on the show. Thanks, Phil. So I don't know if I'm talking to my audience now. I don't know how much you've been listening to our podcast program. I hope you have been. But Dr. Snyder is a regular contributor, and he has done a series of podcasts on all sorts of topics, including marketing, a practice, hiring, and systems. He talks a lot about systems. So to begin this particular podcast, let's talk about clinical applications for ceramic versus zirconia. What are we looking at as far as the materials themselves as being different? And why would we use one over the other? Well, you know, both have unique characteristics. So for indirect restorations, the way I view it is I'm looking at color and strength. And at the same time, I'm looking at thickness as far as how much tooth structure I need to reduce. So when I think of like lithium bisilicate, something like an Emax, I go, okay, strength properties, let's call it a ballpark 500 megapascal strength. Based on that, probably not what I want to have for a full coverage crown in the back of the mouth if I got someone who's a heavy grinder, someone who's really heavy functionally. And so I go, okay, well, maybe for better strength properties, instead of reducing a bunch of tooth to make my Emacs really thick, well, then I'm going to use Zirconia, which has like 1,200 megapascals of strength property to it. And so I'm thinking in that sense for like pressure, but then you go, okay, well, what about like if I'm just doing like a simple inlay? Well, I don't need 1,200 MPs of strength for an inlay. I can do something like the Emax that has, I would say for most people, a simplification of adhesion because they're comfortable and used to it. But also at the same time, it doesn't need the same strength and it has great optical properties. And then you go, okay, well, in the front of the mouth, if I'm doing a bridge, well, depending on how many units that is, I need strength. So I'm going to zirconia. And then you go, well, if it's only like a three-unit bridge, then it's something smaller. You could do something like Emax. And then you go, okay, well, what about like veneers? Well, the majority of people are using like Emacs, but you'd be surprised how many zirconia products out there nowadays can be extremely thin and very translucent and yet still derive better strength properties than an Emacs. And so you look at that and go, okay, if I got to lengthen someone a lot or open their bite, then zirconia sometimes becomes really relevant at that point. So speaking clinically, tell us the difference between, if there is a difference, between the prep design for ceramic, lithium disilicate, and for zirconia and then how does the actual cementation process differ well with zirconia it's said to have about eight tenths of a millimeter necessary for thickness versus you know emacs lithium disilicates typically want more like a millimeter and a half and that's for strength to be a standalone product so you go okay if i'm just going to loot something in with the traditional cement like a resin modified glass onomer or you know a therisem from bisco which is a resin-based self-etching type of system. You go, okay, if I'm going to use one of these and I only have, let's say, eight-tenths of tooth reduction, then I'm going with zirconia because the zirconia has that strength property, which requires me to take a less tooth structure off. Now, for some reason, I'm doing a bunch of, let's say, Emax restorations, and I have like a premolar where I've got, you know, millimeter half, two millimeters of reduction. So I've got the strength required for that particular material and they're not a heavy grinder or heavy occlusal problem type person. Then I go, okay, I could cement that technically too. So both are cementable when they have the right amount of reduction, giving them the strength to be a standalone product. You can use traditional cements. So you talked about the reduction of tooth structure and which material is best suited for each clinical situation. Do you sometimes manage the VDO in all of this? Yeah. You know, we reposition the jaw and change, you know, position such that you've, what would appear to be more space between teeth. Some people would say, you know, changing the VDO. Yeah. So when you have more space, potentially you're taking less tooth structure away by creating space for restorative materials. And so in doing so, you might be still on enamel in certain places. So then it becomes fun. You go, okay, if I can loot with a... resin, you know, adhesive-based system, whether it be light cure or dual cure, and I have a bunch of enamel to grab onto. Well, now I can take either a thin zirconia or a thin lithium disilicate Emax because it derives its strength now from being adhered to the tooth as opposed to just using a traditional cement where you need to have bulk of ceramic thickness for strength. Now I don't because I'm laminating something onto the occlusal table, and when I laminate that and adhere it, it becomes kind of like one. Right. Kind of a monoblock type of thing. And it drives significant strength because of the underlying tooth structure. So in that sense, yeah, opening vertical, I can get away with taking less tooth structure off and using either material at that point. I've talked to several dentists that like to use direct restorative on the molar area directly onto the cusps to open up the VDO. Is that something you typically do or have considered? Well, you know, a lot of different beliefs on how to do things, right? I can't say there's any way that's wrong with that. But for me personally, I like to change someone's bite on something that I can reversibly change instantly. If I have adhered composite to the occlusal table, I can't just instantly take that off and put them back where they started. You can try, but you're always going to make things different. So for me, I typically use some type of orthotic. a kuzal guard of sorts that I can modify and change with acrylic resins. And if something's not working, I can just take it right out and I'm done. So I see people building teeth up with composite. I see people building things up with temporaries. But for me, it's like, well, if you can't back out of that and things go sideways, you're going to have a difficult problem. So me personally, I build it up with orthotics. So there's no doubt the dentist needs to understand the materials. from the standpoint of aesthetics and strength and so forth, and be able to take that understanding and parlay it into the clinical case. But part of this whole equation is the laboratory for most of us, unless you're chairside milling. How important is it to have good communication with the laboratory so both the dentist and the lab could come up with the ideal material for a particular clinical case? Well, you know, I think it's different for every office. I think a lot of times, depending on the lab, the lab just does whatever the dentist says. um whether they approve it or not you know and some of them may be bold enough to step out and say hey doc i think we should use something different me personally i see them as like being my like my left hand like my right and left hand have to work together so before i start a case i have a conversation with the lab as far as like here's what i'm planning on doing as far as my preparations here's what the teeth look like i'm thinking i want to do such and such type of ceramic Does this sound like it works for you or is there something better we might be doing or things that I'm not considering that would make life better for you that you can give me the product I'm looking for or the desired appearance that the patient's wanting? Or, hey, if I want to use Therasem and Zirclean on a Zirconia crown, that's my thought process versus them saying, no, no, no, you're going to have small preps. You're going to have to be using Emacs and using full-on adhesive bonding capabilities. I want to know and understand all that from every angle before I ever get started. So my lab and I have a lot of communication. I would say that's probably not the norm. I would say most. time the dentist sends something and says, just build it for me and don't give me any feedback. I just want this, get it done, get it back fast, right? So when working with both ceramic and also zirconia, we have a choice of using the adhesive method or typical traditional looting cementation. What goes through your mind to make that decision to go either way? Well, obviously if I'm working on a front tooth, I can pretty much isolate and keep things dry. So in the front of the mouth, Really, I'm deciding on my preparation design, the material I'm using, that it should be very easy to adhere something using resin technologies and to keep restorations thin, whether it be zirconia or Emax lithium disilicates. I'd say where it becomes a little more challenging is the thought process, the mental gymnastics that go into the posterior dentition, where if you're doing one crown, it's not typically much of an issue. by itself because you can isolate one tooth or you can use a traditional looting cement. But where the gymnastics comes, if you're doing multiple restorations and you're going, okay, I've got numerous teeth I've got to put in back here. Do I have enough tooth structure? How hard is it going to be to keep saliva at bay and fluids, blood and sulfur fluid, et cetera? And you go, okay, so can I isolate? If I can't isolate, then I'm thinking I've got to do something different in my preparation design or I've got to use different material that I can truly cement in and know that it's going to work well. If I know that I can't loot something in with traditional cements, then I'm going, okay, now it's going to be more challenging. So how am I going to make this work? Do I need to make something thicker so that I could use a cement? Or am I going to have to go to zirconia instead of like a thick lithium bisilicate and then use cement? Or will I have the ability to, let's say, isolate the first molars and I can use resin adhesion and take less tooth off. But let's say the second molars, there's no way I can isolate it well. And so I've got to go back to traditional cement. So I'm kind of thinking about all of those the day that I'm working on. I'm like, how challenging is this person going to be when they come back in two to three weeks to deliver that final product? So I assume on the bigger cases, you do some pre-planning with your prep design, perhaps working with models and waxing up ahead of time. You know, anytime I'm doing, you know, full mouth rehabilitations or big cosmetic cases, I tell everyone to always prep the teeth on a model before you ever send it in to do the wax up. So the laboratory sees what you're intending on doing as far as your preparation design. And you're saying, here, here's my preps. Now critique them, but also wax things up for me. And so from there, they can say, well, we see what you've prepped, but it's not going to work well for us. We want you to prep more in this place or that place so that we have enough fitness for our material to do the right type of appearance that you're looking for. And so right there becomes a huge communication change that most of us don't seem to have. And therefore, I think you run into more problems. But for the same token, nothing is 100%. Even though you pre-prepped and you practiced and you had communication, you get into the patient's mouth and you find that maybe on a back molar, you thought you were going to go one way. The next thing you know is underneath the tooth is totally gone. It's mush. And you got to take out a bunch of decay. And you're going, OK, audible. I don't have the tooth. Just do a minimal prep here and just put something in with traditional cements. And now I'm thinking like, oh, I'm going to have to use adhesion. Or now it's going to be harder because. isolation in their mouth is challenging. And so how am I going to build this up or change this so maybe I could use a cement? Do I have to put a buildup in? You know, like, so I think no matter how much you prep, you may find things that just don't work in your favor. But I'd say at the same token, the more you prepare, the less surprises you get when you're doing bigger cases. So let's say you look back, Dr. Snyder, over the last five years, are you doing more traditional looting of your crowns, whether it's ceramic or zirconia? Or do you find yourself depending on the adhesive technique that we discussed earlier in order to cement these crowns in? Yeah, that's a great question. I would say for ease of use in the back of the mouth, obviously cementation becomes fast and easy. And so I want fast and easy if it truly gives me a benefit and it helps the patient, because ultimately it's about the patient. And so I look at things like Bisco's Therasim. and or like doxoceramir, some of these newer bioactive type looting cements that provide, you know, really great adhesion and truly provide a benefit as far as healing to the tooth. And so I try to use those in the back of the mouth, you know, premolars and molars. So when I'm prepping the teeth, I'm thinking about that, having that in mind as far as my preparation design, axial wall height, taper and all those fun things. But, you know, sometimes you take off, let's say, an existing. you know, adhered lithium disilicate crown or partial coverage restoration, you realize that there's not enough tooth to create ideal situation for a crown prep. And you're going, okay, it's not ideal. So in this case, I know I'm going to have to adhere things in. And so knowing that, okay, I can create still retention for my inlay, onlay, poor kind of fitting restoration, you could say, and switch, you know, call an audible and move to a resin looting cement, whether it be a light curable or dual curable product. But I'd say the back of mouth, majority of the time I'm trying to cement because I think there's a benefit for the release of ions that these modern bioactive cement types of things have. What's the downside of using adhesive cementation with all the crowns that you do in your practice? I mean, I know it's a little bit more time consuming, but I would assume there's an advantage to that. Or do you think it's just overkill and we're not helping anything with recurrent decay? We're not really sealing up the margins any better by using adhesive materials? in that cementation process and going with traditional looting cement is just as effective as long as you have the right prep? You know, that's a great question. And I don't think anyone has the answer because materials continue to change. And we need to go back and look at things in, you know, 20 years from now and see, you know, what worked. I will say that obviously the challenge is technique sensitivity, you know, dealing with what part of the tooth you're working on, the substrate of it, and then what bonding agent using, what type of resin. You know, all those intricacies have to play really well together. And you think of like immediate sheer bond strength. Like a lot of times you can see dentists take phenomenal materials and they get poor bond strengths. Other times they'll use it and get lucky and get great bond strengths. You don't know what bond strength you're getting unless you're testing. So in that sense, I go, well, gee, there's a lot of variable there. So hence I go, okay, when resins fatigue and fail, they leak and eventually create a problem. Well, we can't diagnose those well because radiographs don't look through ceramics really well. So with all that in mind, and then you think of like bonding agents degrading from MMP activity inside the tooth, and you go, well, then maybe in the back of the mouth, if it were me or for my family, I'm going to put one of these newer, more bioactive materials that still derives, you know, 20-something megapascals, let's say, of strength to zirconia, and it has a good bond to the tooth. But it's an insurance plan under there, hoping that it's fighting off. you know, bacteria and potential cavities and things that maybe it buys more time. And that's why I use those for the most part in the back of the mouth wherever I can, because I feel it's giving the patient an opportunity for a longer lasting restoration. Versus in the front of the mouth, it's almost always adhesion because of minimal preparation design. Any favorite go-to bioactive cement that you really like to work with? Well, as far as like releasing calcium, you know, and fluoride into the tooth, I like the Theracem from Bisco. It's got some great properties to it and great adhesion to zirconia and other ceramics. So in that sense, I think it's really well thought out adhesion that they've come up with. So I like the science and research behind it. And so that's one of the products that I like to use. All right, Dr. Snyder, appreciate your input and your recommendations. Thank you very much. And we look forward to having you on future podcasts as well as webinars. I know you have quite a few coming up on Viva Learning. So to our audience, check out Dr. Snyder, S-N-Y-D-E-R. Simply visit us at VivaLearning.com, do a search for Dr. Snyder, S-N-Y-D-E-R, and you can sign up for his upcoming live webinars. Thank you very much again, Dr. Snyder. Appreciate it. Thanks, Bill. 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