Navigating the Maze of Dental Ceramics and Cements

You're listening to the Phil Klein Dental Podcast. Choosing the right ceramic materials and understanding their properties is fundamental to achieving optimal outcomes in restorative dentistry. We all know this, and that's why it's important to understand the nuances behind different materials. Ranging from traditional feldspathic porcelain to cutting-edge ceramics and zirconia, each material has its own set of advantages and considerations. Moreover, selecting the appropriate dental cement and mastering effective adhesion techniques are crucial for ensuring the longevity and stability of your restorations. In this episode, we'll explore the characteristics of various ceramic materials, delve into the nuances of different dental cements, and discuss best practices for achieving reliable adhesion, empowering you, the clinician, to make confident decisions in your daily practice. Our guest today is Dr. Effie Habsha. She is a prosthodontist practicing in Toronto, Canada. She is an adjunct assistant professor at the Department of Dentistry at the University of Rochester and an associate in dentistry at the University of Toronto. And also, Dr. Habsha is the founder of Women in Dentistry, Work, Life. Balance, a group dedicated to educating, elevating, and empowering all women in the dental field. She lectures nationally and internationally on various prosthodontic and surgical topics. Dr. Habsha, welcome to the show. Thank you. It's a pleasure to be here, Phil. You're tuning in from Toronto, beautiful place to be. A little cold, but I hear great things about Toronto. I have not visited Toronto. It's one of the parts of Canada that I have not been in. I've been to Montreal several times, so that's on my list. You'll tell me which restaurants to visit when we get there. You'll have to come up. Yeah, definitely. No, I hear it's beautiful. So we're certainly happy to have you on the show, Dr. Habsha, because the topic of ceramics is certainly a keen topic right now among dental practitioners. We have to also consider the use of zirconia. And part of all this is our prep design and conservative prep design. Minimally invasive dentistry is a big factor. And that also goes along with our adhesion process, because if we're not reducing the tooth very much, we're not really focusing on the retentive prep necessarily, for instance, with veneers or onlays or inlays. We're more interested in the adhesion and tooth preservation, possibly even going to, in many cases, zirconia with the more aesthetic zirconias that are out there. So to begin, tell us the different types of ceramic materials to start that we have. at our disposal? Sure. Absolutely. I think when you think of dental ceramics, you have to think of them in terms of three classifications. And the first one being your flutzpathic porcelains. The second classification or broad classification is your particle-filled glass. And the third is your polycrystalline ceramics. So in general, if I can kind of give you an overview of each classification, your feldspathic are your beautiful, highly translucent, highly aesthetic. ceramics. They're glassy matrix, they're very beautiful, but they're inherently weak. So the flexural strength for your feldspathic are anywhere from 60 to 70 megapascals of strength. flexural strength and in order you know then you can ask well how can you use such a weak material in the in the oral cavity and and the answer is is it relies on the adhesion so the bonding of the material to the two structures so generally the only indication really for feldspathic porcelain is for porcelain veneers and and specific types of porcelain veneers laminate veneers where you have a lot of enamel you don't have a lot of unsupported porcelain because that would be susceptible to fracking that's, in general terms, your feldspathic. So again, highly aesthetic, but very weak. And so in order to improve the strength of these glass ceramics, the second classification that I will cover is the particle-filled glass. And so with this classification, you essentially have your glassy matrix, but then it's infused with some particles to strengthen it. So those particles can be, you know, the most typical product or the most common, I should say, product is a lithium disilicate infused material, which we know commercially as EMAC. So it's a lithium disilicate particle filled glass. You can have lucite filled, you can have other, you know, other types of fillers into this glass ceramic to create a particle filled glass. and these materials have a broader range of indications so they can most certainly be used for porcelain veneers, whether they're laminate veneers or veneers that have some unsupported that have some that are unsupported with two structure. So they can be used in that indication. You can use them for full coverage restorations in the anterior, certainly in the posterior with certain indications and for partially partial coverage restorations as well, like inlays and onlays. And historically, I mean, you can use them for select fixed partial dentures, but. Generally, you know, if I'm doing a fixed partial denture in ceramic, I'll use a zirconia based material. So with this classification of material, the range of strength is anywhere from around 200 megapascals to 500. So it's much stronger and you don't necessarily need to rely on your bond because we're going to talk about cements later to gain strength for the materials. So that's the second classification. And the third. is your polycrystalline ceramic. So polycrystalline material. So this material is really, it's a misnomer. It's not a ceramic because there isn't a glassy matrix. It's a polycrystalline structure like zirconia. So a bunch of crystals in the case of zirconia, zirconium dioxide, which are used to form this ceramic type of material that we know commonly as zirconia. And these materials, dependent on the amount of yttrium in the composition, can be highly aesthetic, so quite, you know, translucent and aesthetic. Or the stronger, you know, the 3YTZP, which is, you know, your higher, sorry, lower concentration of yttria is what we know conventionally as our... you know, conventional zirconias or our stronger zirconia, which can be, which are strong as, you know, about 1100 plus megapascals in strength. Historically, there used to be an inverse relationship between aesthetics and strength when it came to ceramics. So the more aesthetic the material was, like our feldspathic, the weaker it was. And the less aesthetic material, like our zirconia, were much stronger. But now with new materials in the marketplace, new research and development, we have highly aesthetic material, sorry, very strong materials like your 5YTZP zirconias that are quite strong. And conversely, you can have aesthetic materials, well, aesthetic materials that are stronger as well. So that divide between materials is becoming less stark. And we can really use all ceramic restorations in any indication in dentistry. So do you think the new materials are helping us with a minimally invasive dentistry where we're not removing as much tooth structure? Could you give us an example? of how the newer materials are giving us the aesthetic value that we're looking for, but also the strength and allowing us to preserve valuable tooth structure in our tooth preparation. Absolutely. I think that's a really good point. You can have very minimally if you want a full coverage restoration rather than having, you know, one and a half millimeter axial reduction or occlusal reduction and one. plus millimeter axial reduction, you can go as thin as 0.5 millimeters with a monolithic zirconia. Adhesive dentistry or partial coverage restorations, a combination of materials that are etchable and bondable plus cement, which again, we're going to get into, can allow us to do more minimally invasive dentistry. So inlays, onlays, partial coverage restorations, which I'll tell you, the Europeans are very into. North Americans aren't as much anymore, but that pen... shifting that, you know, I am personally in my practice doing a lot more partial coverage restorations under the proper indications with the proper materials, the proper preparation guidelines, as well as proper bonding and cementation, because that's the key. You need to have that trifecta, you know, appropriate prep, appropriate material and appropriate bonding in order to achieve really predictable and long lasting results. Are you doing a lot of milling chairside in your practice? I am not milling chairside, no. It's a great workflow, but in our practice, being a fairly busy prosthodontic practice with our own in-house lab and the digital technology that we have. I am fully digital in my practice, so I don't really impress anything anymore from tooth supported restorations to implant-based. And that workflow for the volume that I have just doesn't make a lot of sense for me. We did try it. We did try it. But it just didn't work for our workflow. And I'm, you know, I hazard to say that I think that you can get, you know, for complicated cases or comprehensive care, maybe I shouldn't say it, but I think certainly in my hands, better marginal and fit in an internal fit with, you know, either pressed restorations or milled in the laboratory. But certainly, I mean, it's a very... know, common practice to have chairside milling and a lot of successful practices work that way. But personally, I prefer to use my dental laboratory. Yeah, no, I hear that from a lot of key opinion leaders and thought leaders out there. What was originally thought to be something that was going to be adopted by almost every dentist, which is chairside, hasn't really happened quite that way. And lots of different key opinion leaders have their own reasons why they... are not using chairside for most of their work. And they really like to rely on their laboratory, their outside laboratory for a lot of reasons. Yeah. And some do the design work in-house. Some love their labs and just like to really just focus on the actual in-mouth, in-operatory treatment as a clinician does and have the lab worry about the fabrication of the restoration. So let's talk about cementation for a minute. There's a lot of confusion. among dentists because, you know, there's a lot of different cements out there. There's different ceramic materials, as you just described. So with your experience as a prosthodontist, what are your recommendations on how best to navigate through the choices that are available now with cementation? Sure. Another really good question. And I think that there's often a lot of confusion by dentists. And I certainly teach a lot of dentists, both at the student level, undergrad, grad, but also dentists that are taking continuing education courses. And one of the biggest challenges that we have are, you know, Effie, what cement do you use? Like, just give it to me straight. What do you use? What's your favorite cement? And I think that... like ceramic materials, you have to classify your cements into categories. I like categories. And so if you think about your cements, because there are hundreds of cements in the marketplace and each manufacturer having their own type and a bunch of different manufacturers. So, you know, if you want to navigate through the choices, you can think of your cements in three broad categories. One category, which is... you know, tried and true cements that have been around for over 100 years, like your zinc phosphates, your polycarboxylates. Those are your conventional cements. And conventional cements rely solely on micromechanical retention. So there's absolutely no adhesive property to that. So cements in that category, like I said, you can have your zinc phosphate, your polycarboxylates, your resin-modified glass ionomers, Reliax, a looting cement, which is a resin-modified glass ionomer, is also by 3M as a conventional cement. So that's your... general category of conventional cement. So if you think of it in a pyramid, the bottom of your pyramid is your conventional cement. The very top of your pyramid is your adhesive cement. So you can have cements that rely solely on bonding or on chemical adhesion of the restoration to the tooth. And so those, you know, on an extreme level, think of a veneer. There's no resistance or retention form. There's no you know, if you had micromechanical retention, it wouldn't last because you need that bond strength. So in that category of cements, you know, the ones that might be familiar to our listeners are your Relyix veneer cement, your Nexus cement for veneers, Varylink aesthetic. That's your adhesive cement where you're relying solely on bonding. Somewhere in the middle or right smack in the middle, about 15 or maybe 20 years ago, you have the development of the workhorse cement in most practices, I think now, which is your self-adhesive cement. So that category has the best of both worlds. It has the ability, the micromechanical features of your conventional cement and the ease of use and bonding that, you know, that the conventional cements offer. But it also has the bonding capabilities of the adhesive cement. So it's the best of both worlds. And the cements that fall into that category, again, if we're going to talk about brand names and the ones that might be familiar to our listeners, are your Reliax cements, so Reliax Unisem by 3M. More, most recently introduced the Relax Universal by 3M, which we can talk about because that's a really good cement. Speed CEM by Ivoclar and Max CEM. So those are just some of the self-adhesive cement. So as I said, the benefits of the self-adhesive, and I think most dentists, at least most that I talk to, like to use those because they offer the ease of use and a reduced number of steps, just like conventional cements do, but then they also offer the adhesive properties. of your adhesive cement. So in general, those are your classifications of cement, your adhesive, your self-adhesive, and your conventional. So you've certainly covered the categories of cements very well. How do we make the decision as clinicians as to what cement is really best? for the situation so that depends on what you're looking to bond it depends on three things number one what restoration you're looking to bond is there enough resistance and retention form where you don't necessarily need the adhesion or are you looking at a veneer where you have no resistance and retention you're only looking at adhesion so based on your restoration a full coverage restoration or one that has, you know, really good resistance and retention form, you can use your conventional cement or your self-adhesive cement. Conversely, if you're bonding a veneer or a partial coverage restoration, you want to get that adhesion so that you would use the adhesive cement. So like your, you know, your adhesive, solely adhesive, and then anywhere in between. So for me, Most times I'm using a self-adhesive cement because... Unless I'm doing a veneer or a partial coverage restoration, that's what I use. The other factor you have to consider is what material are you bonding? So are you using something like a feldspathic? If you are, then of course you're going to need to gain strength of that material by bonding. So your adhesive cement works well there. Do you need extra retention from the bonding? So again, a self-adhesive or adhesive cement. Or do you have a very strong material like zirconia where you're not really relying on the cement to make it strong? So then you can use your conventional or your self-adhesive cement. So let's talk about resin cement. What are some of the properties we should be looking for in a good resin cement? I look at essentially three properties that I think are most useful. Number one, obviously, is the bond strength. So, you know, if you're using resin cement. You want it to have a very high bond strength to work very well. I would say from a practical standpoint, your cleansability. So I've used cements in the past, you know, self-adhesive cements that were just a pain to clean. So I would spend a lot of time cleaning after. So again, if you have high volume and you're kind of working at a good clip and you're probably, you know, cementing multiple restorations, you want something that's going to be user-friendly so cleansability is really important um you know certainly because your cement can dictate the ultimate shade of your restoration it's nice to have a cement like the the new um relax universal that has a multiple you know multiple shades to choose from so whether it's clear to white or um you know yellow that that's really nice as well. And I think, uh, radio opacity is also really good. So to be able to discern, you know, whether you have recurrent decay or, you know, carries under a restoration or the cement. So I think, you know, if I were to summarize my four top, um, parameters, it would be bond strength, of course, um, cleansability, the color stability or the ability to modify colors. If you wanted to certainly color stability is another one. And finally, radio opacity. So now that you've confused us a little bit more about which cements, no, I'm only kidding you. I mean, listen, more information, of course, can be confusing. It would be wonderful if, you know, a cement was available where it literally did everything. I think we're getting to the point where we... Your self-adhesive kind of hits that. Your self-adhesive has the beauty of your conventional and your adhesive. So that's exactly what you're wishing for. It does exist. You just have to know when to use it and when not to. Well, that's what I'm saying. So that's where the confusion lies. But let's say, how much damage would a dentist do if they strictly relied on a self-adhesive cement for everything? I mean, what would be the downside? I don't think there would be a downside. except for the scenario where you require uh you can use a self-adhesive cement in an adhesive protocol so if that makes sense you know if you're looking to increase your bond strength so self-adhesive if you would work, but to get a little bit more, you know, adhesion, you can, your protocol for bonding could be adhesive protocol, meaning you would etch your tooth and you would apply bonding resin. So when you talk about self -adhesive, what makes it self-adhesive is all the formulations for the chemistry, the bonding is inherent within the cement. So you as the dentist, you treat it like a regular. conventional cement but the chemistry is in there to make it adhesive but in a self-adhesive property you can if you want added adhesion prepare your your restoration by etching it or by you know priming it and prepare your tooth by etching it and placing bonding resin to make it self -adhesive so really i think you know a cement like your um relax universal can be used in a self -adhesive capacity, but it could also be used in an adhesive capacity. So I personally use a self -adhesive cement. for everything with the exception of using an adhesive cement for my partial coverage and veneer restorations. Some people really like resin modified glass ionomers, obviously for the fluoride. So I, you know, for sure you can use that. But for me in my practice, my kind of workhorse cement is my self-adhesive cement. Okay. Well, that does help a lot. So what do you say to the dentist who says, well, I'm going to wait a little bit. longer until the research really shows definitively that zirconia is a material that you can get effective bonds to. Now, I know you're bonding to zirconia in your prosthodontic office, right? So tell us how you're doing that and what kind of success you're getting. And what would you say to the dentist who's kind of reluctant, more in the wait and see stage of his or her career saying, I'm going to wait and... I don't want to find out three or four years from now that my zirconia is going to be popping off. I think that's a really good point. And, you know, I think that we have materials that have stood the test of time. Obviously, you know, going back to full gold crowns, PFMs, we know that they work. But I think it's time to kind of embrace the present. It's not the future. I mean, zirconia has been around for a really long time. Same with these all ceramic materials. And they're backed with... really great research and literature out there. So it's not, you know, I certainly would not introduce that in my practice, nor would, you know, millions of other dentists if it was kind of a trial and error thing. So let's go with the premise that zirconia is here to stay and it works. And I think there's only going to be improvement in the materials. And the concept or the... about zirconia i mean really it's not such a scary material to bond it's it's people you know think that you can't um well zirconia isn't etchable it's you can't bond it you can't etch it because it's not there's nothing to etch there's no glass it's a it's a polycrystal material but what you can do i mean the purpose of etching a material is to get uh rough and surface so what you do with zirconia is you need to air braid it before you bond it and so it you know in the very popular article and and um you know by my by marcus blatz where he describes the apc concept air abrasion primer and cement it's a very simple matter of air braiding your restoration clean and there you know i'm not going to get into the details but air braid your restoration and clean it properly clean your tooth properly apply a primer in your restoration however that primer can be bypassed completely because a lot of your cements already have an mdp primer embedded within them so really for bonding quote unquote zirconia you need to air braid your zirconia clean your tooth properly you can bypass a separate step for a primer because most cements already have an mdp primer in it and then just use your self-adhesive cement one that contains the mdp primer in it so it's a very tried and true and predictable way to essentially bond or loot or cement zirconia onto your restoration and i you know Of course, from a literature standpoint, there's a lot of research out there. But, you know, anecdotally in my practice, I have thousands of restorations bonded with zirconia restorations that, you know, touch wood, are still doing great and holding on strong. So I would encourage any dentist who's on the fence to get off that fence and certainly incorporate these all ceramic opportunities and solutions into your practice, understanding the material and understanding how to bond it properly. Yeah, well said. In closing, do you want to tell us, Dr. Habsha, about your women in dentistry? program that you founded you've had it for you've been running it for 14 years so we have a lot of listeners so I'm sure they would be very eager to hear about it as we wrap this up sure well thank you for thank you for bringing that up yeah I mean I like many of our listeners I wear you know who wear many hats I too wear many hats and one of my hats that I wear is being the founder of a group called women in dentistry work-life balance and you can check it out us out on instagram at women's dentistry plural women's dentistry or women in dentistry.ca. And it's a group that we founded 14 years ago with a real mission of educating, empowering and elevating all women in the dental field. So we're really proud of it. I'm really proud of it. Our annual symposium is coming up and it's expanded over the years. It's blown up to many, many attendees. So if you want more information, go online, women in dentistry.ca. And, you know, we'd love to get more, more eyes on the. website and more attendees and, you know, to spread the message and the opportunity to network and connect. Yeah. And I've heard many, many great things about your program, Dr. Habsha, from people that I've interviewed, women that I've interviewed, women dentists, Dr. Rainey, Dr. McMahon. and others. And they found it to be one of the most important things they've done in dentistry is to be part of the group that you founded. So hats off to you for that. I hope it continues to be successful. Thank you. And thank you so much for your contribution today. Really enjoyed it. Thank you so much. It's my pleasure. Thanks, Phil. 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.