Unlocking Adhesive Excellence in Zirconia Bonding

You're listening to the Phil Klein Dental Podcast. Most of us have started using zirconia as a material for our indirect restorations. We either mill it chairside or send it out to the lab. Either way, we need to make sure that our technique is perfect when delivering it to the tooth, especially if we are working with a non-retentive prep, because if we need to rely on adhesion, we have to understand the nuances of bonding zirconia to tooth structure. To fill us in on the things to be concerned about and proper technique and materials is our guest, Dr. Alex Vasserman. Dr. Vasserman is a respected clinician running his own practice on the Upper East Side of Manhattan. Dr. Vasserman, it's great to have you back on the show. Hi, Dr. Klein. How are you? Things are going very well. Thank you, Dr. Vasserman. I appreciate it. So zirconia is all the rage these days. So it's not surprising that there are many discussions on whether you can actually bond the material to the underlying tooth structure. Many experts say that you can, but there are still some that are not convinced. They feel that it's difficult to establish a good bond with zirconia. What are your thoughts on this? Yeah, depends on which study you read and depends on who you listen to. And the question is, does MDP, which is going to be the key to all of this, increases bonding or adhesive retention, as some people call it? And what does do the study show? Yes, zirconia is the new rage. Why is zirconia such a good material? Zirconia is such a good material because of its compressive forces. In our previous podcast, we discussed that second molar that's beat up in relation to the first molar and the premolar. Well, some patients... a lot more force on that second molar because their joint isn't seated all the way or because they're just landing really heavy on that second molar compared to everything else. So are we comfortable with putting a ceramic restoration like Emax on the tooth or do we want something stronger? And when you look at the studies, can you bond zirconia or not? To be honest, it doesn't matter what you call it. whether it's bonding or increased retention, I will still go minimally invasive and put zirconia on it as long as I get ahead of it and tell the patient that perhaps that this restoration may come off. But I rather be minimally invasive and use a stronger material versus over prepping the tooth, doing a cohesive restoration. but that may lead to post-operative issues like pulpal involvement and needing root canal treatment. We talked offline, Dr. Vasserman, about an interesting way that you present to the patients the idea of adhesive dentistry used in your indirect restorations. And it explains to them basically that using an adhesive technique is more conservative and what the pluses and minuses are. And you do this by actually showing them a model or dye. Explain to us what you actually do. So I have the restoration on the dye that's minimally invasive, that looks like an onlay or a three-quarter crown, something like that. And then I have another dye where it's a full prep with a crown over it. And I discuss with a patient that I, you know, whether they have these really big pulp horns that I don't feel comfortable shaving the tooth down 360 degrees, that I want to do minimally invasive dentistry and I want to use a material that's much stronger. I don't go into the science with them and tell them, you know, compressive forces. I just say that it's a much stronger porcelain. And it doesn't glue as well. But in my hands, I, till this day, I've done a lot of these minimally invasive zirconia restorations. I have had very, very, very few of them come off. So what you're saying to the patient is that it's beneficial to them to stay minimally invasive with the downside of the adhesive part of the process failing potentially, where they would come in with the restoration in their hand but meanwhile the underlying tooth structure will be preserved and can be restored again where for the rest of their life hopefully they'll have that tooth versus that right versus the flip side which is what we discussed in an earlier podcast which i found very interesting the patient is then presented with the idea that you know we could put something in that may be more aggressive as far as retention but that could lead to more chances of post-operative sensitivity, and as an endodontist myself, of course, popal involvement. So are you seeing success with zirconia on non-retentive preps? How much of a track record are you looking back at in your office to be able to evaluate the success of these non-retentive preps with zirconia? Yeah, at this point, I've done probably a few hundred non-retentive zirconia restorations. There have been very few cases where the restoration comes off. Of course, failure is inevitable whether you're using lithium desilicate or whether you're using even composite. We all deal with failure. But I find that the amount of failure that I'm having where the restoration comes off typically has to do when the cement is actually in the restoration so that tells me that i probably don't didn't have enough enamel to bond to it's very rare that when the restoration i haven't seen it yet where it comes off and the cement is on the tooth and not in the restoration so to me um the the failure isn't that the cement is debonding from the zirconia. It's debonding from the tooth, which is telling me that I probably didn't have enough enamel. Would I still do it? Yes, because I can always then go cohesive. I could rebond and buy this. onlay or three-quarter or non-retentive restoration a few more years just by rebonding. And our cements are also getting a lot better. So perhaps in two, three years or five years, my cement may be a little bit better. Maybe the MDP is going to get better. So the amount of failure doesn't change my mind whether I'm going to go non-retentive zirconia. And I've done a bunch of them. I've done hundreds of them at this point. Maybe one year, all hundred will come off. I don't know, but I'm still doing them. So tell us real quickly, and you did cover this in previous podcasts and webinars, Dr. Vasserman. Tell us your process chair side, how you bond zirconia to the tooth. Right. So let's say I get the zirconia from the lab. I will remove the temporary. I will try in the zirconia. Let's call it an onlay on that beat up second molar where I didn't have enough. reduction room the amount of reduction that you need for zirconia is a millimeter whereas for emacs is a millimeter and a half with a large pulp horn, sometimes that could be, you know, a difference between needing a root canal and post-operative sensitivity and not. So when I get that restoration and I'll try it, I'll make sure the occlusion is correct, that I can get my floss through, that there's a snap. Sometimes I don't even break contact. So that's not an issue. The first thing I do after the try-in is we're going to prepare. The zirconia restoration. What do I do? I'll take my particle abrasion. I use a prep start unit. It's chair side. It's tuned to one PSI. It has 50 micron aluminum oxide in it. I keep my tip about a centimeter or 10 millimeters away. And I'll particle abrade the entire. inside of the surface. Will I clean using Zirclean? It's a cleaning agent to remove glycoproteins sometimes, but from some of the data that I've read. the particle abrasion itself gets rid of those glycoproteins. It also increases micromechanical retention. If you look at some of Nate Lawson's work where he uses ECM, he shows what the zirconia looks like when you're particle abraded versus you don't particle abraded. When you're particle abraded, it creates these little tiny grooves or notches or like holes in the zirconia where the MDP in the cement The second step is I'll take Z-prime. It's a primer, MDP-containing primer, and MDP is the key to bonding these non-retentive zirconia restorations. MDP uses one side where it bonds to the phosphate groups of the zirconia, and on the other side, it bonds to the OH groups of the resin cement. no pun, it's the glue that holds it all together. Without MDP, I don't think it's going to be possible to bond these non-retentive preps. So then I'll scrub the inside with MDP or Z-prime, and I set the restoration aside. On the tooth, it's the same process whether I do Emax or filtopathic porcelain. This is my steps. I always make sure that there's enough enamel all the way around because bonding to dentin is not very predictable. So what I do is I particle abrade the entire restoration. Particle abrading dentin decreases sensitivity and also increases micromechanical retention. Same on the enamel. Again, look at Dr. Lawson's work where he shows ECM pictures of particle abraded dentin and enamel versus not. And then I'll only selective etch the enamel for 20 seconds. I'll selective etch enamel only. I'll clean it. And then I'll air dry it. I will use two coats of All Bond Universal by Bisco. I'll scrub it for 30 seconds. I'll air thin it. I'll scrub it again for 30 seconds. Air thin that. Cure it. And then I'll load the restoration with, I will use two things. Either I will use heated composite or my go-to these days is Dualink by Bisco. It's a really predictable cement, easy to clean up. I load the restoration. I'll seed it over the tooth. We'll tag cure it, clean up the cement, floss the contacts. And I will cure it again. Dial in the occlusion, polish, and that's it. And so far, that has worked very well in my practice. I've been doing that for about three to four years now. And the amount of failure where it debons is very, very low. And you don't do chair-side milling because you have an office in the Upper East Side of Manhattan with limited space. Is that right? That's exactly it. I just don't have the space for a milling unit. And also, I don't have the personnel to mill and then polish, glaze, and prep. I send this out. I make my temporaries. I can bond the temporaries. I'll spot bond, spot edge, and use a little bit of either flowable cement or there's a wonderful temporary cement from Ivoclar that I will use. And my temporaries typically don't come off. If they do, it's rare. And then, yeah, I don't mill in the office. My ceramist will mill out the zirconia restorations. I get them back in about a week, 10 days, and then the patients come back. I'll numb them up and cement the restoration. What about printing your provisionals? Do you have a 3D printer? Yeah, I do print for bigger cases where I'm phasing treatment. It's wonderful. I use SprintRays crown material. I still won't definitively put them in. I'll put them in if I'm phasing. So if someone needs like a full mouth rehabilitation, I'll print out X amounts of crowns, cement them all, and then convert. two or three at a time, if they want to maximize their FSA or insurance, or they can only do two, three crowns a year, then I'll just move them and replace them either with Emax or zirconia. If I'm afraid that their occlusion is, you know, if they have parafunctional habits, if they're grinding, if they're clenching their teeth, I will more likely for the second molars and first molars go zirconia. And then for premolars, pressed Emax. That's my go-to. And then the anterior is feldspathic porcelain. Do you see down the road that as the zirconia materials become more advanced, adding more aesthetic characteristics to it, and there's gradient zirconias out there right now. I think Ivoclar has one where they're adjusting the 3Y, 4Y, and 5Y, giving it the strength where it needs to be and more of a translucent characteristic in the occlusal level or the incisal area. Is that something you see will move the needle to where we're primarily using zirconia and these other materials are going to kind of go by the wayside? Yeah, I think that zirconia is getting, once more and more data, long-term data comes out for the longevity of zirconia, that patients aren't breaking zirconia, I think a lot more dentists are going to turn to it. And MDP is the key here, the Z-prime material. That's the key here. You want to have a lot of tools in your tool belt, Emax. Like I said, I sometimes will still use gold in the posterior. I think it's a wonderful material. You want to be kind of diverse in the materials. But yeah, I think the more and more data will come out, I think the more and more dentists won't be so afraid of bonding zirconia. And the last question about zirconia, what about... how hard it is, how does it behave in contrast to the opposing tooth? Is there any wear situations that you're concerned about on the enamel? As long as you don't glaze the zirconia, on all of my prescriptions, it says do not put glaze. on it. And you've heard of Brock's ear. He said the reason why it's so good in the opposing tooth is because if you look at microscopical substructure of zirconia, it's very dense. So it's very smooth. So as long as the data that we've had before where it wears the opposing tooth structure, it's when we apply glaze to it. Glaze is very harsh in the opposing tooth. Even when I restore implants, I will always say do not apply glaze to the zirconia. Polish only. And as long as it's highly polished and my protocol after I dial in the occlusion, because sometimes it could come back a bit high, I will use a fine diamond. I'll dial in the occlusion with a fine diamond. And then I have these polishers from Clinician's Choice. There's a blue and like a gray one. It's a coarse and a fine. And I will polish it until it's very, very shiny. And as long as it's polished and then there's no friction, what I'll do is I'll put horseshoe paper and I'll have the patients chew. And as long as there's no big blue streaks on it. we're fine. I don't see any wear on the posing tooth structure. I don't see post-operative pain. And it's a very strong restoration. In terms of compressive forces, it's double. If you're looking at like a 3Y zirconia, it's like triple, maybe double the compressive strength of something like Emax. So they tend to not chip. Dr. Vasserman, thank you very much. Really enjoyed your talk. And we really appreciate all your contributions on the Viva platform. Looking forward to having you on again. Always a pleasure. Thank you so much, Dr. Klein, for having me. 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.