Zirconia Mania: Why the Rage and What to Look For?

You're listening to the Phil Klein Dental Podcast Zirconia, arguably the most popular and talked about material in indirect restorative dentistry. To tell us why the rage and what to look for is our guest, Dr. Larry Grillo. He is the founding partner in a three-partner, three-associate practice in South Florida. He has over 30 years of experience in general practice with an emphasis on aesthetics, implants, crown bridge, and veneers. Dr. Grillo lectures nationally and internationally on dental implant therapy, new technology, and dental sleep medicine. Dr. Grillo, it's a pleasure to have you on the show. Bill, it's a pleasure to be here. Thanks for the invitation. Yeah, we're very happy to have you, and zirconia is certainly a buzzword, big, big buzzword in dentistry today, so it's great that we're doing this podcast. So to begin, give us a one-minute overview of zirconia and share with us the key advantages and disadvantages of the material. Well, certainly. I have been at this long enough that I saw the advent of zirconia replacing some of the other restorative materials that were used historically. Zirconia is wonderful because it gives us the strength. of a metal ceramic reconstruction. So you can use it for single unit. You can use it in multiple unit. You can use it in long span bridges. You can use it for implant supported restorations. It's hard. It's not flexible. It allows us to opaque some of the substrates of tooth or metal underneath and still come up with a really nice, pretty aesthetic restoration on top. It comes in different types of zirconia that are used in dentistry. There's always a balance between the strength of a material and the aesthetics of a material. And zirconia, as of late, has the ability to have both. Depending upon what type of zirconia we use, we can have it more translucent and allow us to give us the strength and stability that we need. So what type of zirconia is most commonly used in dentistry, and what are the new innovations with zirconia? When we talk about dental zirconia, it typically is what's referred to as a yttria-stabilized polycrystalline zirconia oxide. So it's kind of a long word for dental zirconia. Within that subgroup, over the last multiple years, they've started to work with the amount of yttria, the amount of stabilizer that's included in that substrate on the zirconia. So they talk about a 3Y, 4Y, 5Y. That has to do with the concentration, how much molar by molar concentration of that stabilizer that's inside the material. And the lower that number, like a 3Y, gives us a lot of strength, a lot of flexural strength, somewhere between 1,200 and 1,500 megapascals of flexural strength. Just to give you an idea, traditional feldspathic porcelain is somewhere between 100 and 200 megapascals. significantly stronger than what we see with traditional ceramics. As we go higher in that yttria stabilization, you're going to see more and more translucency, more and more lifelike, more and more depth, but you trade off a little bit of the flexural strength of that. And so we use it in certain applications and we use some of the other materials in other applications. So when it comes to the dentist working with the lab, is it the responsibility of the dentist to make sure the right zirconia? is prescribed for that patient, meaning that the dentist really has to understand the materials and the clinical application. So as in a lot of things in dentistry, there's a partnership between the dentist, the restorative dentist, and the laboratory technician. And I'm really hands-on. I'm anal that way. I want to be involved in the process of what we're using each step along the way. I've also been spoiled because I've had the opportunity to work with an amazing technician for the last 20 plus years. He's actually right here in the office. So I've learned so much sitting side by side with him. So we talk about the relationship between the dentist and the restorative, sorry, the technician as being like scissors. Either side of that scissor really doesn't work by itself. So ideally, both parties really need to know what they're talking about. Ideally, it would be good if the dentist kind of talks to the technician and says, I'd really like to use 3Y on this because this patient is a Bruxer. Big time parafunction. When I look at the other ceramics in there, they've blown the porcelain off the metal underneath or they've got a lot of parafunctional wear. So I want to have that. And the technician may not be aware of that and want to go with a 4Y or 5Y to get that more beauty, more translucency. The longer the spans, the less ytria that you want on the inside. No, that covered it well. So if the span is long, even though you're looking for aesthetics, you still have to really move towards the 3Y, correct? That's absolutely correct. So with that, with that 3Y stronger material, you also get a little more opacity. Some of the very first zirconia products that were available in dentistry, like Procera, they were dead white, flat, and you use them basically as copings or cores underneath. And then we would fire feldspathic porcelain on top of that. And there are still some applications where we can fire feldspathic porcelain on top of the zirconia. In our practice, we've gotten more and more and more away from that and working with some of the new gradient style, which allow us to have both 3Y, 4Y, 5Y, or mostly 3Y and 5Y. So it allows us to have the strength where we need it down low at the abutment level and at the connector level. And as we get closer and closer to the inside of the ledges, we get more of that 5 -1. You get the best of both worlds. Yeah, and that's what I want to talk to you about next, which is a great segue here. So Ivoclar has really come up with a game-changer technology, and they call it gradient technology, I believe, and correct me if I'm wrong. And they've really made it simpler for both the dentist and the lab by creating somewhat of a universal puck. But that universal puck... like you said, has the 5Y in the incisal zone, and then it moves down to the 3Y, which is a strong oxide ceramic in the Denton zone. Tell us about that gradient technology in that puck, and there's different versions of that puck. One is primarily a universal one, which covers a lot of cases, but then when you really want the aesthetics, there's actually an aesthetic version of that gradient puck. So talk about that if you would. That's exactly right. And it really is a game changer because historically, just like we talked about before, there's always been this conversation of how strong do we need this to be? What is the application going to be like? And I'd really like to have something aesthetic. You have somebody that has a high smile line, somebody that's relatively youthful, want to have that beautiful translucent look. You had to trade off always strength for aesthetics. And with this technology, you don't have to. Gradient technology by Ivoclar really make a difference. There are multiple manufacturers that will make a block that has different layers in it. So you have 5Y on top and you'll have 4Y or 3Y below. So the difference in the gradient is that you have this beautiful transition from 3Y to 5Y that's seamless. And the analogy I like to use, it's like the difference in a pair of bifocal glasses. where you have both, but you can see clearly where the lines are and they're harder to work with, they're more obvious, and a set of progressive glasses where it's smooth, even transition, and it works as you look up and look down, but you can't really see that there's this differential in there. And I think that the gradient achieved that for us. So I assume that the gradient technology is patented by Ivoclar, although the other companies have the layered blocks, but they're not transitioned in a gradient fashion. Well, the truth is, you'd have to talk to Ivoclar about that. Knowing the company like I know the company, I'm pretty sure that that is patented proprietary material. We've been working with gradient technology, or rather we've been working at layered technology for a long time. We worked with lithium disilicate, the Emax materials. We worked early on, Rafa and I, with some of the materials that have gradient on the inside. So they were pressable ceramics. They'd have a warmer shade for... the gingival portion you have a more translucent lighter shade toward the incisal but the technique of spruing and how that came about was pretty technique sensitive and oftentimes you could see that transition line as the material flowed in with the gradient technology you really can't see it but you really do get the best of both worlds it's really strong makes our connectors rigid so we don't have to worry about fracture at the connector level and you still get those beautiful incisal edges that create some some translucency So the two pucks we're talking about, correct me if I'm wrong, Dr. Grillo, is the IPS-EMAX ZERCAD Prime, and that's the one that has 1200 megapascals of strength. And then we have the IPS-EMAX ZERCAD Prime Aesthetic, and that has 850 megapascals of strength. And I assume that's because there's more 5Y or 4Y added to the puck. So let me know if that's correct, if I got that right. And also tell us the clinical applications for these two pucks. So the answer is you're exactly right. You described exactly what takes place. And when you give up the 3Y with that flexural strength, what you're going to give up is the longer span bridges. So anything that has multiple connectors, anything where you're going from the anterior to posterior, where you're going to get some significant torsion, you really want the 3Y there to give it that backbone and that strength. If you're going to do three-knit bridges, or if the shade of the tooth underneath is a little lighter, so you can do lighter preparations as well, You need more translucency to match the adjacent teeth than the aesthetic. The prime aesthetic allows you to do that in single units and in as much as three-unit bridges. So, Dr. Grillo, do you think you can achieve similar aesthetic results as you did with lithium disilicate in the past when using the Zorkad prime puck? Well, that's an interesting question. And actually, Rafa and I have been doing some cases over the last year or so where we've had cases with the anterior teeth. For example, tooth number eight. has been endodontically treated, the root is dark, it's stained, and it needs a full coverage crown. The tooth adjacent to that is worn, or we don't like the proportion, so we want to do a veneer on the adjacent tooth. And I want to conserve as much tooth structure as possible. I want to use the Emax because of the ability to etch the intaglio surface. My bond strength with the Emax, I'm really comfortable with as a veneer. At the same time, I want the strength and I want the masking ability. of that zirconia to be able to mask out that substrate and that darker and when you put them side by side if i give him enough space and what's enough space if i give him a millimeter on the zirconia and if i give him seven tenths of a millimeter on the the veneer you can't tell from one to the other they're beautiful transitions and again it depends on the technician you're working with the experience they have with these materials but with rafa you really can't pick which one's zirconia and which one is z -mac We all wish we had a lab technician like you have, Dr. Grillo. Amen. Yeah, right. Hold on to him. So let me ask you this, and that's also great that you talked about preparation because do zirconia crowns require special preparation? I assume they need a little less reduction than lithium disilicate. That's exactly right. And Emax, because it's got about four, depending upon which study you look at, 450 to 500 megapascals of flexural strength. On posterior teeth, you actually want a little more occlusal reduction. You want a little more reduction to add the strength by using the bulk. Whereas with zirconia, if I've got a posterior tooth that's a really short walled tooth and I'm tight on occlusion, I really want to use zirconia because I'm comfortable at a half a millimeter, five tenths, with an occlusal surface on a second molar, and it's not going to fracture. So typically, zirconia preps, because of the strength of the material, the inherent strength of the material, less tooth reduction. True. It's exactly right, especially occlusally. The other thing that's nice about zirconia in terms of preparation design, if you like to prep butt margins, you can do a butt margin. If you like to do chamfers, light chamfers, deep chamfers, even as fine as feather edge margins because this material mills and holds up so beautifully, the marginal fidelity is so good, you have a lot of flexibility on how you prepare the marginal portion of the tooth. If you're going to mask the color of the tooth underneath and you're going to use something like the the aesthetic, prime aesthetic, then you want a little deeper chamfer, you want a butt margin. But if you have a lighter tooth color underneath, you can really refine these super thin and not have to worry about fracture or breakage, and the accuracy is beautiful. So do you see with these advancements lithium disilicate kind of going by the wayside, which was obviously the most popular indirect material for many years, I believe? I'm going to say absolutely not. With regard to full coverage crowns, I think you have a lot more flexibility with strength, anyway, and lots of different applications using the Zirconia product. So a full coverage, especially in a posterior tooth, I think that's kind of the go-to. But I still love, I like to do really, really conservative preparations. I like to maintain as much enamel as I can on the tooth. We do a lot of veneering, a lot of partial coverage, and in cases like that. To be able to etch that glass surface and get that superior bond strength that actually adds to the overall strength of the restoration as well, I still love to use Emacs, and I don't think that's going away anywhere. There is some bonding to the zirconia, but it's not as predictable and it's not as strong as the bond we get from these etched glass ceramic restorations. So let's talk about cement now. What type of cement? should be used for the zirconia restoration? And would you use the same cement for anteriors and posteriors? So I can tell you, I've tried pretty much everything. We haven't used traditional flex cement on those. But early on, as these restorations were coming out, we tried a lot of different cements. And without belaboring that and going through it, we've come down to some of the work by Marcus Blatt. It's probably the best material you're going to see out there right now in terms of looking at the studies and figuring out how to do that. Routinely, we like to use resin-modified glass ionomer cements. That's what we want to use. But we want to definitely prepare the surface of the intaglio surface of the zirconia restoration before we use that cement. We want to use aluminum oxide in a 50 micron size at about two bars of pressure. And what that does is surface roughen the interior surface, so you increase surface area and surface roughness. So you get a better bond to that. We tried a lot of things also after that. Steam cleaning, lots of cleaning. And what actually Marcus' work also showed, that some of that alumina actually gets embedded microscopically in that intaglio surface. And it actually helps with the chemical bond strength. So we go straight from sandblasting. We blast it with air. We use an MDP primer. It's a 10 MDP, which is a word that's long enough that I'm not going to be able to pronounce tonight. And then we can use our resin-modified glass ionomer cements to loop these in place. So no matter how great a dentist we are, we all see some failures. It'd be interesting to hear from your experience, Dr. Grillo, what you typically see when a lithium disilicate crown or... does fail. And hopefully that doesn't happen too often. And the same with zirconia. Tell us about the cases you see that do fail and what you actually see clinically when the patient returns to the office. Oh, like every dentist, we have no failures. That's right. Yeah. The truth is, if we have a failure with EMAC, it's either... problem at cementation that I'm not paying attention. My assistant has put Vaseline on the patient's lips. I look away, the patient closes, and they contaminate that service. Doesn't happen very often, but I know it can happen. Routinely, Emax stays beautifully laminated tooth structure. Really strong, really durable bond, and I don't get the chipping we used to get with traditional feldspathic veneers, parafunctional brinders, people that have airway issues, and that kind of stuff. What I will tell you is my experience was that on posterior teeth, specifically on second molars, where I'm a little tight and occlusal clearance because I'm trying to maintain wall height, I have had some of those Emax grounds over a period of two to three to five years fracture. And when they fracture, they fracture catastrophically. They shear through and you'll lose half of the restoration. Conversely, with zirconia, that's why we went to zirconia on second molars almost routinely. Because when these do fail, they typically don't break. And I'll typically see them at two to three years out on a parafunctional grinder that wasn't using their night guard and don't have an airway appliance. And they're grinding cyclically over and over and over again. They come loose. And they'll tell you the same story we've all heard. I was biting on a piece of cheese. I was biting on a piece of bread. And it typically is something a little sticky that lifts the crown off. And they'll bite down on it sometime, but they don't break the crowns. The crowns always come back intact. But they also tell you the tooth is comfortable. It doesn't hurt. It gets comfortable. Well, it's because when we do have those failures, it's always between the surface of the resin cement and the intaglio surface. It's always got this beautiful little bond of cement sealing up the dentinal tubules and sealing everything up so they're comfortable. So at that point, we'll typically go back in. re-sandblast the internal surface, make sure we're using MDP primer because this may have been just before the MDP primers were used. That's why we failed. We'll also go back to the tooth and try and remove that old resin because we know that we don't get great bond strings to old cured resin. And I've tried it with Diamond Burr, but what I've gone to as of late is we have a laser. It's actually a modified CO2 laser. And we can preferentially go through and remove all of that cement off the tooth, re-expose the dentinal tubules, and then rebond. And my hope is that in another five years, those are going to be intact and in good shape. So as we wrap up this podcast, Dr. Grillo, I think it's obvious to all of us, based on this conversation, how important it is as dentists to really understand the materials that we use in our prostheses. And in addition to that, it's super important to have a very good relationship with the lab that really understands the materials we're choosing and prescribing for our patients. I think that's absolutely accurate. I think having that great relationship between the laboratory technician and the restorative dentist, and quite honestly, the manufacturer of the product. IvoClar, we've been working with for 20 years. And I will tell you, all of this information is readily available to the clinician as you go online. And they're super helpful with helping you understand some choices that you might want to make and suggestions you might want to make. So their support and their backup and their information technology is really, really great. to be able to help make those decisions. But you really want to understand the pros and cons of the different kinds of materials, where the applications are going to be. But these newer materials are going to make a lot more places where we can utilize these materials. It's an exciting time in dentistry and really appreciate your input, Dr. Grillo. And we'll look forward to having you on future programs down the road. Thank you very much. It's a pleasure. Thank you. Talk to you soon. If you're enjoying this podcast, please leave a review or follow us on your favorite podcast platform. It's a great way to support our program and spread the word to others. Thanks so much for listening. See you in the next episode.