Dental Cements...Making Sense of it ALL!

Welcome to The Dr. Phil Klein Dental Podcast. I'm Dr. Phil Klein. Dental cements have certainly evolved over the years. Up until the late 70s, we pretty much relied on only one cement. Today, we have more than five different types of cements. And to make things more complex, these newer cements have all kinds of dispensing and mixing methods, as well as a broad array of setting mechanisms. This can be very confusing, not only to the clinician, but also for the dental assistant. To help clarify things, we welcome our guest, Dr. Taiseer Sulaiman, Associate Professor and Director of Advanced Operative Dentistry and Biomaterials Research at the Adams School of Dentistry, University of North Carolina, Chapel Hill. He has published over 80 peer-reviewed articles, abstracts, and book chapters, and has lectured on numerous national and international stages. Before we get started, I would like to mention that Dr. Sulaiman’s webinar titled Making Sense of It All, State-of-the-Art Dental Cements is now available as an on-demand webinar on VivaLearning.com. Simply type in the search field Sulaiman, S-U-L-A-I-M-A-N, and you'll see it. It's an excellent webinar for the entire dental team. Dr. Sulaiman, it's a pleasure to have you on Dental Talk. Thank you very much, Dr. Klein. It's a pleasure to be here with you once again with Viva Learning. Yes. Yeah, we appreciate it. And this is a pretty important topic. I mean... routinely use cements probably several times a day, I would assume, especially with the popularity of ceramics and CAD CAM and everything else they're doing in the office. Any type of indirect restoration requires cement, obviously. So to begin, tell us about the different types of dental cements available in modern-day dentistry. Well, you know, I'd like to start off by saying that... unfortunately to this day we don't have one cement that can be used for every indirect restoration so that requires us to understand what type of indirect restoration we have in hand and what we What's the ideal cement to be used for that indirect restoration? And so to organize our thoughts, let's classify the cements according to the conventional cement. So you have, of course, the zinc phosphate and polycarboxylate, if they're still around and existing in your clinic. We have also the glass ionomer-based cements. And I'm going to put the resin-modified glass ionomer into that category of conventional cements that really require proper resistance. and retention form. So just the fundamentals of fixed prosthodontics are applied here and they work very well when you do have a proper resistance retention form. So that's the conventional cements. And then we have, we can classify the resin cements according to their method of curing or pulmonaryization to a light cure resin cement. And then we have a dual cure resin cement. And we have, of course, the self cure or the auto cure resin cement. So that's in according to the mode of pulmonization. And then we can also classify some of these modern day cements according to their mode of bond to the two structures. So we have self-adhesive resin cements and we have adhesive resin cements. And so just by understanding that classification, it kind of helps organize your thought a little bit and into what is indicated for every specific indirect restoration. So with these new modern day cements, Dr. Sulaiman, Is it necessary for us to pay strict attention to proper retention and resistance form going forward? In our modern day dentistry, we are relying more on bonding to the tooth structure. And I think we have been fortunate with the evolution of these resin cements that bond so well to the tooth structure that allows us to be more conservative to the tooth structure and rely more on bonding versus relying on... on grinding more tooth structure to allow for proper retention form and so a lot of the retentive features that we're getting from from modern day restorative or minimally invasive techniques relies on bonding to the tooth structure and that's where a lot of the confusion happens and and that's where you really need to know the differences between the different types of cements that are available because one can perform better in terms of strength to the tooth structure and that will allow you to be minimally invasive and so um And so, you know, if you asked me that question, you know, 10, 20 years ago, I would say, yes, of course, we have to rely on retention form and resistance form to loot or to cement these restorations. But now with the ceramic partial coverage, onlays, overlays, and even veneers, we can be very conservative to the tooth structure and rely more on adhesively bonding these restorations in place. So talking about bonding. What are the protocols for bonding glass ceramics, specifically ceramic partial coverage restorations? So whenever we have a glass ceramic material, the ideal preparation of that material is going to rely on the use of, it's a combination of hydrofluoric acid etching, so micromechanical retention, and also relies on silanization. So a chemical bond is developed between the ceramic and the adhesive and then to the tooth structure. And so, you know, whenever we do have a glass-based material, we want to dissolve parts of that glass and to create that micro-mechanical interlocking with the resin. And so that's why we rely on hydrofluoric acid. we commonly know hydrofluoric acid is having two concentrations in our practice it's the five percent and the ten percent and each specific glass ceramic has a requirement for the the the concentration of the hydrofluoric acid and the time of application those are very crucial for any clinician to follow because there's been a lot of research into testing out different formulas and different application times and and the ones that we have well documented now really involves the um the use of of of either the five or the ten percent but for a defined time i'll give you an example feldspathic porcelain It's predominantly a glass matrix. And so you want to use a 10% hydrofluoric acid to be able to dissolve and to create that proper bond with a micro mechanical etching. And you want to apply it for a minimum of 90 seconds. And again, the concentration and time play a very important role because if you applied it for a longer period of time, you're going to see these salt residues that develop on the intabular surface of your restoration and the salt residues are identifiable by just, you know, using a 2.5 or even a 3x magnification loop. You don't require specific microscopes to to show that and you can determine between an over etched glass ceramic versus a properly etched one and those salt residues that do develop will um affect the bond strength to the tooth structure and so to overcome them if you do realize that on the entire surface is to use um ultrasonic bathing has been a proper way to to clean the surface from these salt residues, and you put them four to five minutes in the ultrasonic bathing machine, and that should take care of that salt layer and remove it successfully. And so if you move into, for example, the lucite reinforced glass ceramics, this requires a 5% hydrofluoric acid for 60 seconds. So now we change the concentration and change the time of application. And then moving into lithium disilicate. for example, which is reinforced with lithium disilicate about 70% by volume. So we have less glass in that ceramic. And so a 5% hydrofluoric acid for 20 seconds is ideal to create a properly etched surface. We have other categories of ceramic material that are, for example, hybrid ceramics. This polymer infiltrated ceramic network is predominantly a ceramic mesh infiltrated with a small amount of about 15% of resin. And because of the predominance of the glass matrix, then of course, 5% hydrofluoric acid is required for 60 seconds. um i i try to highlight as best as possible that knowing what concentration to use and and the time and about 90 of of my work is with the five percent hydrofluoric acid with these modern day ceramics i only have used for the 10 percent um for the feldspathic porcelain when i'm doing veneers so it's become very rare that i'm using the 10 hydrofluoric acid um and some ask you know can we play around with like using a 10 on it on lithium disilicate but reduce the time it really doesn't work that way again they've tried all these different combinations and and and the the concentration and time that i highlighted is the most ideal for these glass ceramics and then you move on with the salinization process and then applying the adhesive depending on what system you're using, to continue forward with properly creating a clean chemical bond to the ceramic material. Because chemical bond is what we've learned is most valuable, especially to a dentin substructure, something that we were missing 20 years ago when we didn't know how to properly bond to the dentin. But now we're starting to figure that out and we understand its importance. If we follow the right protocols, we should not be seeing debonding failures in our practice. When we talk about bonding protocol for zirconia, what are the best practices that dentists should be aware of? when they're handling zirconia so zirconia is a is a different beast here that we're dealing with due to the nature of of the material itself it's a it's a polycrystalline um structure and so we don't have glass in zirconia we cannot etch it with the conventional methods that i just described with the glass ceramics and we had a lot of debonding failures over the past decade or so with zirconia, which led to many to believe that we cannot bond zirconia restorations. I think that information is outdated. We have very good evidence that we can bond zirconia to the tooth structure if we follow a very strict bonding protocol. and that really involves two things it's a micro mechanical again interlocking or a treatment they call it the mechanical pre -treatment and then you have a chemical pre-treatment the mechanical pre-treatment involves the use of airborne particle abrasion and again a lot of research has been done to show what is the ideal protocol to follow to create an ideal surface for bonding zirconia. And that involves using particles no larger than 50 microns for about 20 to 30 psi pressure at a 10 millimeter distance for about 10 seconds. And again, researchers have tried different combinations to see what is the most ideal bond strength that they can get. And what I shared with you is the most ideal to create an optimum. uh surface to bond to it and the chemical pre-treatment involves using silanes that contain the mdp monomer which is a magical monomer that creates a very nice and strong chemical bond to the zirconia and a lot of the modern day adhesive systems have the mdp monomer in the composition since the patent expired. Cori was the first who came out with this and the patent expired and so many of these companies have included this monomer in their adhesive system and that's been working phenomenally well to create this nice chemical bond to zirconia. What we failed to understand before is the affinity of zirconia to salivary lipid and protein contamination and also from the blood during try-in and that creates a a layer that really is hard to get rid of through conventional methods that we used for glass ceramics. And so we now see these zirconia cleaners that are available in the market. And we've published on the most ideal way to clean the entire surface. After you try it in the patient's mouth, you must remove this contamination to create an optimum bond to the zirconia. And just to keep it simple for folks listening that The protocol that I personally follow is that after I get the restoration back from my laboratory, they know that they're not supposed to touch the entire surface. That's something I take control of. I also do for the etching process for the glass ceramics as well, because technicians might try to treat the surface in the most ideal way they think is proper, but no one should know this information better than the clinician applying themselves. And so I do that process myself. And so when I get the crown back, I try it in. And after I'm satisfied with everything, I go into my lab and I do the airborne particle abrasion because Doing that at that particular time is going to do three things. First of all, it's going to clean the surface the best possible way of mechanically detaching all the contamination. It's going to create an optimum rough surface for bonding, and it's going to create an optimum prime surface, which means that the surface energy is very favorable to receive the ceramic primer afterwards and allows it to create an optimum bond to the zirconia surface. air bone particle abrasion at that step is the most ideal way and then i go out after that my surface is ready and prepared i put my ceramic primer and let it sit for a couple of minutes because i want the ceramic primer to penetrate as best as possible and then i use a dual cure resin cement um and because zirconia attenuates light and i want to make sure that enough energy is passing through the zirconia and we've published work that shows the 20 second time is really not enough to cure the resin properly i always advise to double the curing time for each surface so about 40 seconds assuming you've selected a proper curing light 40 seconds for each surface so that you can ensure enough energy is passing through the zirconia to create an optimum polymerization for that um seminary material and so that's the protocol that i've been following and and you know it's been around for quite some time now and And I haven't really been seeing any debonding failures. Yeah, zirconia certainly seems to be the prevailing. material lately. It's trending across dental practices all over the country. And so it's important that that bonding protocol is adhered to, obviously, to maintain a successful restoration long-term and getting predictable results. So let's talk about cements for a few minutes as we get towards the end of our podcast. What cements are recommended for aesthetic restorations? And I assume color stability is an important criteria here. yes and so you know um if you have a thin ceramic restoration that you're using for aesthetic purposes for example veneers you really want to rely on on a a cement that is light cure only you know we've shown again through aging these cements that they are color stable and they won't change in color with time you don't want your cement dual cure that has the amine component as an initiator that will change in color with time and that will show through your ceramic restoration and really disappoint your patient after a while. Cure Cement, and I've used Reliax Veneer, for example, from 3M is a great product that does have a light cure cement only that you can use. for these veneer restorations and you know other dual cure cements that do have the amine component in them you got to be aware that they will change in color with time there are new cements that have been introduced that are claimed to be amine free and that they have different initiators and they're claiming that they are color stable we're doing research on that right now just to see how color stable are they but for these expensive restorations i'm not really willing to take the risk yet to do use dual cure cements that are immune free. And some have already been using them. And I'm really looking forward to see the three or five year outcome from photos to see if they are color stable. But for the time being, I think the light cure cements are the safest to use. And what I follow in my practice to make sure that the cements don't change in color with time. The Reliax product line has several different cements in it. Yes. Is there any way you can clarify the difference between these? And so what 3M has done really is color-coded the cements, but they did that to avoid confusion. And so you have the pink is the Rely Excluding Plus. That's a resin-modified glass ionomer, ideally to be used with restorations that have proper resistance and retention form. And it's been my go-to cement for PFMs and monolithic zirconia. When I have proper resistance and retention form, I don't even bother with bonding it to the two structure because I'm relying more. on my retention form in my preparation. And then you have the self-adhesive Reliax Unisem is yellow color-coded, mostly indicated when your retention form is questionable and you'd like to rely on more bonding to the tooth structure. They have self-etching primers in them that that work very well to bonding to the dent and surface. And then you have the green color coated is the Reliax Ultimate, and that is the adhesive version of the cement. And that's the highest bond you can get to the two structure recommended for these partial ceramic crowns that you really want to, that you're relying on the retention from the bonding protocol and the bonding procedure versus your retention or resistance form in the preparation. 3M and other manufacturers try to do is combine, you know, cements into one cement to see if you can do that and they came out with a relyx universal cement which can be used in a self-adhesive mode and and you can use it in an adhesive mode as well if you combine it with the scotch bond universal plus what's remarkable with that cement specifically what we've been seeing from in vitro studies is that the when it's used as a self-adhesive so excluding their adhesive. Compared to their own Reliax Unisem, it's about double, sometimes triple the bond strength. And that's quite remarkable for a self -adhesive cement to have that strength of bond to the tooth structure. And so, you know, if you think about that, you really are not needing to use that Unisem or the Ultimate anymore, because now the Universal replaces both of them. You can use that as a self-adhesive, or you can, if you need more retention, you can use the Scotch Bond Universal. plus and it transforms into an adhesive resin cement to optimize the bond strength to the two structures so that's specifically focusing on the 3m system and that has been around for many years and there's been a lot of research on on their products so we are getting close to the point where we can really reduce our inventory when it comes to cements using the system that you just described. Yeah, especially if our studies are going to show that they are color stable as well, then they can replace the Reliax veneer like your cement. And, you know, to use the Reliax universal in a self-adhesive mode should be fine or adhesive mode to bond your veneers. And if the color stability is not an issue, then that takes care of those types of specific, you know, aesthetically demanding restorations. Dr. Sulaiman, thank you so much for your time. Great podcast. So much insightful information. We really appreciate it. Thank you very much. Absolutely. Thank you very much. I appreciate your time.