The Latest on Materials and Bonding Protocols for Indirect Dentistry

You're listening to the Phil Klein Dental Podcast So there are quite a few materials to choose from these days when it comes to our indirect restorations. Today we'll be talking about the popular ones and we'll also be discussing how we get them to stay on the tooth. Meaning, do we go adhesive or cohesive? And what are some of the materials we should be considering? To tell us all about it is our guest, Dr. Alex Vasserman, a practicing dentist in New York City who always pursues cutting-edge care for his patients with a focus on minimally invasive dentistry. Dr. Vasserman, it's a pleasure to have you on the show. How are you, Dr. Klein? I am doing very well, thank you. It seems like we've been doing one or two of these a year, so that's good. We'll keep it in touch through our podcast program. So to begin this one, in a time where dentists have so many different... indirect materials to choose from. What are the most commonly used materials in the profession today? So when talking about indirect restorations, of course, the go-to, and I still think it's the godfather of restorations and people are still using, is your metal ceramics, right? That's your PFM restoration. I still see a lot of it. I speak to my ceramist. And a lot of the dentists are still very much comfortable. prepping underneath the gum, creating that feather chamfer, seeding the restoration. The metal ceramics, I still think are a go-to. In my office, I primarily use either lithium disilicate. My go-to is the pressed. I don't mill in the office. I usually ask my ceramist to fabricate if I'm going to go with lithium disilicate and I'm bonding the restoration. And again, whether you're bonding or not, you could still do lithium disilicate. The properties of lithium disilicate are very good, even on first, second molars, pending that there's no high occlusal forces, bruxism, you know, anytime when you're looking at that second molar. If everything, if the first molar and the premolars are really nice, but the second molars are beat up, that gives me a red flag. Perhaps I'm not going to use lithium disilicate on there because even though I could get my 1.5 millimeter reduction, which is what you need for lithium disilicate, perhaps their joints aren't seated. Maybe they're really landing heavy on those second molars. So maybe in that situation, I won't use lithium desilicate. Maybe I'll use something like zirconia or even gold. I still do gold once in a while. When a patient is okay with using gold, if it's on the upper second molar, I'll have the discussion with them. Gold restorations, you could still bond. You could still get really predictable. cementation technique on there. So I will use gold once in a while. Pressed Emax is my go-to. Tell us briefly, Dr. Vasserman, the difference between pressed Emax and milled Emax. Milled restorations come in a block and you pick the color. The crystals on the milled restorations are a little bit bigger. Technically, in some studies, they do show that they do have about 100 megapascals more compressive forces versus pressed Emax. But my go-to is the pressed. What they do is they print. I scan 90% of my restorations. I have an iTero element scanner. I scan for single or two units. I'll scan the prep. And in my prescription, I'll say pressed Emax. My ceramist will then wax the pattern, which technically is a little bit better marginal seal. Because when you're milling, that burr has to be really precise. But when he's layering wax on it, he can cover up little discrepancies or, you know, open margin, that sort of. that sort of a thing. And I'll ask my ceramist to make me a pressed Emax restoration. So in terms of cementation, talk about adhesion versus cohesion. Whether you go adhesive, it's a flat top restoration, or a cohesive where you have that perfect prep, six degrees of taper, at least three millimeters of ferial, preferably five millimeters of height. You can go cohesive or adhesive, right? You could sit the restoration on top. You could bond it if you want to. You don't have to bond it. Of course, a bonding technique is going to be a little bit more challenging than just a cohesive restoration. So you mentioned to me earlier that you still use felt spathic porcelain. With all these advanced materials, you'd think that would be going to the wayside, but you still use it. Felt spathic porcelain is... the weakest restoration. It's the most brittle. But once you cement it and adhere it to the tooth, if there's plenty of enamel, it becomes very strong. That's Pascal Manier's work where he showed that once feltopathic porcelain is bonded to the tooth, it becomes a lot stronger. The analogy is when you're fixing like a bathroom tile. The tile itself is very weak, but once you cement it onto the wall, it becomes a lot stronger. So we hear the term minimally invasive dentistry all the time. And I know Dr. Vasserman, by talking with you, how much of an advocate you are for conservative dentistry, which is so important. So how does minimally invasive dentistry carry over to the way you perform indirect restorations? Yeah. So being minimally invasive is This, I believe, is the gold standard. If you have deep occlusal decay, but the buckle, the lingual, the marginal ridges are okay, you can prep into the tooth. And as long as there's an enamel ring, you don't have to prep those buckle lingual walls, the marginal ridges. And it's important to be minimally invasive because nothing lasts forever, right? That restoration, if the patient is going to live long enough, will probably fail eventually. What's the mode of failure? Either it's going to debond with time, it may break, perhaps the tooth around. But if we're minimally invasive, then there's still a lot of the tooth structure that you could use to restore again. the more minimally invasive we are, the less trauma we're causing to the tooth, less sensitivity. If there's a pulp horn in the way, maybe you can avoid devitalizing the tooth, causing long-term irreversible pulpitis. Let's talk about cohesive and adhesive procedures. And I know you've mentioned it, you touched upon it already in this podcast. Give us more detail about... factors into determining whether you're going to use a looting cement, which is cohesive versus actually going in and doing an adhesive procedure and talk about how it relates to the actual prep design, taper, height of the walls, et cetera. Let's talk about posterior teeth, right? Let's pretend that we have this big MODBL amalgam. We're removing the silver mercury. And when I look at from the bird's eye view from the top, if there is a predictable enamel ring 360 degrees around the tooth, I will go adhesive, meaning I'm not going to create any. tapered walls where i need to grab the restoration mechanically i'm strictly using adhesive protocols where i am gluing to that enamel so what determines whether i go adhesive or cohesive is how much enamel i have around the tooth think of that anterior prep when you're prepping for veneer If you have dentin, yes, you could bond to dentin, but that bond is very unpredictable. And the reason why it's unpredictable is because dentin is very organic. It's wet. It's a sponge. And also it has these metalloproteases in it that over time degrade the bond. Enamel is inorganic. Not only does the resin cement interlock, into the enamel um into the enamel itself but there's also a chemical bond between the oh groups and the phosphate with a with the help of the silane the silane is the coupler that brings the resin cement to enamel yes you could bond to dentin if you particle abrade it but it's not a very reliable bond so do i want to go strictly adhesive when I'm fully indented? No, because the chance of that restoration failing within the first five years are unpredictable. It goes up. So in that situation, I need to grab the tooth mechanically. I will add some kind of retention preps, six degrees of taper, three millimeters of... tooth structure to grab the restoration. When it comes to the material choice, if you realize that your prep is not a retentive prep and you will need to use adhesive dentistry, would you go with Emacs instead of zirconia? I could, you know, I've recently with the help of MDP and, you know, talking to guys like Rolando Nunez. And if you look at some of the work, by Nate Lawson, you could see that they have showed that you can predictably bond zirconia. I have done, remember we talked about that second molar restoration where everything is fine, but the second molar is beat up. But I may not have a millimeter and a half of reduction. I may have only a millimeter because there's a pulp horn in the way, or I just don't have enough occlusal reduction. I will go zirconia, but I will preface to the patient that I have to use a little different ceramic material, zirconia. It's stronger. And if you look at the research, it's about 1200 megapascal of compressive force. So it's a lot harder to break zirconia versus Emacs. So I will bond zirconia, but I will get ahead of it and discuss that with a patient. that there is a chance that it could come off. And if it does, we'll figure it out down the road. But I will explain that ahead of time. If I'm bonding Emacs, of course, Emacs is a much more predictable bond because of the silane, because of the chemical bonding. The research has showed that you can definitely bond Emacs. You can bond zirconia. But the data is a little bit murky on it. I will still bond zirconia and I will still use the same protocol. If I have a non-retentive gold prep, like a gold onlay, I will still use the MDP. I use those protocols, which you and I will discuss later. And yes, I will still bond it, but I will have a discussion with a patient. that because I'm using adhesive protocols and something that doesn't glue so well to the tooth, that perhaps it could come off. But the way that I explain it is because of your forces, I rather have the restoration fail versus the tooth. But if I go cohesive and I over-prep the tooth, now the chances of devitalizing the tooth or creating post-operative trauma go up. So you're basically discussing with a patient that by going with minimally invasive dental approaches, you will have less tooth structure that you're going to remove, which requires adhesive dentistry. But if that fails, the restoration is going to fall off and the tooth will still be able to be restored further. Whereas if you go with cohesive, which requires more tooth reduction, And you run into problems down the road, you're more likely to look at pulpal involvement and possibly a root canal and further treatment that the patient does not want to get into. That's exactly what I'm saying is if I feel like I don't have enough room to over prep the tooth or prep the tooth and go cohesive, and I want to go adhesive, but it's murky and I'm using gold or zirconia. I will still do that and go through my bonding protocols, but I will get ahead of that so that way the patient isn't upset when the restoration is in their hand. So for the most part, do you think most of your patients understand this explanation where you tell them that, okay, we're going to be conservative, we're going to be using adhesive dentistry, but because of that, there is a drawback. You may be coming back to me one day with the restoration in your hand, but at least the tooth structure will be there so we can fix it. Or are they just completely confused about all this? Yeah, and what I do is I have two dyes from previous work, and I'll show the patient the difference between an adhesive prep, where it's just flat, you know, like an onlay with cuspal coverage, or a full 360 degree prep. And I'll explain to them that because of... your tooth and I don't want to over prep it. I'm going to go with this design. This is what it's going to look like. We're going to glue it because of your bite. It's unpredictable. Perhaps they may need a bite recalibration where I seat their joint and recalibrate the whole bite. But the patient understands. that if that restoration for if I go with Emax and it breaks, my explanation to them is I rather have the restoration fail or come off versus devitalizing the tooth or having the tooth break because I underprepped the tooth. What material do you like to use when it comes to adhesive? What is your go-to materials? Usually now, nowadays, I'm almost 50-50. With pressed Emax, if we're talking about posterior restorations, anteriorly, unless it's a bridge, I barely use zirconia. So let's get down to the nitty gritty of all this, Dr. Vasserman. Tell us the steps that you use to successfully... cement in, adhesively first, a crown and then go to cohesive methodology? Sure. So when I don't have any retention, I particle abrade 50 micron aluminum oxide at one PSI, about 10 millimeters away from the tooth. I particle abrade everything. I selective etch the enamel only, and I put two layers of All Bond Universal. It's a bonding agent by Disco. It's my go-to. It's a one-bottle system. And I'll scrub for 30 seconds. I air thin the first layer. I'll scrub for another 30 seconds. I'll air thin the second layer, and then we cure it. The restoration depends on what I'm using. If it's lithium disilicate, After the try-in, I will clean it to get rid of the glycoproteins. How do I clean it? We typically use Zerclean, also by Bisco. It gets rid of the glycoproteins. We also sometimes will take that lithium desilicate restoration and put it in an alcohol bath and vibrate that. Once that's clean and air-dried, I will apply my silane. I use two-bottle system, also by Bisco, A and B. We silinate it, and then I will use All Bond Universal, also by Bisco. I like to just stay with the same company. It's a dual-cure resin cement, and I will seat the restoration, tack-cure it, clean up the cement. However, if it's zirconia, I will particle-abrate the zirconia. You could use Zirclean to get rid of the glycoproteins. Same protocol. 50 micron aluminum oxide, one PSI, 10 millimeters away. We particle abrade because not only does that clean the glycoproteins, but it increases the micromechanical retention. And then I will scrub it with MDP. MDP is the link between the zirconia and the resin cement. MDP or product called Zirclean, Z Prime by Bisco gets scrubbed onto the zirconia or the gold. Same process for metal or zirconia, all bond universal. And then that gets placed onto the restoration. We still tag cure it because the access cement needs to be tag cured. i'll clean that and then we recure just in case i have the patient bite down on gauze for about two minutes and then we clean up the excess cement even more so that's the protocol for adhesive now if we're going cohesive on these materials tell us about that briefly yeah so cohesive to me if you have perfect preps and you have six degrees of taper at least three millimeters of natural two structure five millimeters of prep height look anything works right uh zinc phosphate has worked for years the the example i use when when you get that cement retain implant with a crown that perfectly fit you could use water and it's really hard to remove it right? Anything works at that point. In my hands, what I typically use, if I'm not bonding the restoration, if I'm just using cohesive only, I will particle abrade the tooth. And then I will take the restoration and make sure it's clean, get rid of the glycoproteins, same approach. And then I will use either an MDP containing cement like Therisam. Or you could use Unisam by 3M. I'll fill the restoration and I'll just sit it over the top, tack here, clean up the access cement, floss, and then either have the patient bite down for two minutes. Make sure that that cement is set. Or if it's like an Emax restoration where you could pass the light through, I will cure that. So to me, anything works as long as the prep is perfect. So to wrap up this podcast, and it's been very interesting, Dr. Vasserman, I appreciate your insight and your clinical experience. How would you define success regarding a dental restoration? In the past, we used to say, hey, if we can get five years out of a crown, that's considered a success. Is that the same situation we're in now with all these advanced materials and adhesive dentistry? What is the definition of success in your mind of a dental restoration? For me, it's not just whether the restoration comes off or fails. To me, it's also how healthy can you keep the tooth, right? Like, will the patient need endodontic therapy after the procedure? What kind of a shape is the tooth in when that restoration fails? Five years to me is the bare minimum, right? Ideally, I'd like to get 15, 20 years. Of course, the patients... plays a role, their home care, whether they have root caries, because sometimes that restoration could stay on, but they get root caries underneath it. So there's a lot of factors to play in it, but minimally invasive dentistry really depends on how healthy is the tooth after you're done with it, right? Really appreciate your insight, Dr. Vasserman. Thank you so much for joining us. We look forward to having you on Viva Learning webinars. I know you've done a lot on our webinar programs, and we really appreciate your contributions to continuing education on the Viva platform. Have a great evening. Thank you so much, Dr. Klein, and I'm looking forward to our next discussion. 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.