CAD/CAM Block: The Uncut Gems of Your Office

You're listening to the Phil Klein Dental Podcast In the past, we didn't have many choices when it came to CAD CAM blocks, but today we do. So in this episode, we'll be talking to a dentist who is well aware that Zirconia wins the strength battle, but he has plenty of reasons to stay the course with lithium disilicate. He specifically prefers a lithium disilicate block that saves him the step of firing after chairside milling. To tell us all about it is Dr. Yao Lin Tang, who has over 20 years of practical knowledge in cosmetic and general dentistry. He is a CEREC user since 2005, a certified CEREC trainer, and a visiting faculty at cdocs.com. Dr. Tang, it's a pleasure to have you on the show. Hi, Phil. Thanks for having me here. Yeah, we're really happy to have you. And, you know, there's a big... A question in dentist's mind between using some of these materials these days, especially when it comes to CAD CAM blocks. And I know you're a big fan, just talking to you offline, you're a big fan of lithium disilicate. So we'll get into that later on in the program. But first, I want to begin with a simple question. Why did you decide to become a CAD CAM dentist 18 years ago? I think back to 2005, before that, you know, we, of course, I'm like most of the other dentists that we take an impression, PVS impressions, and we send the impression to the lab and have lab to do all our cranks. And we have been suffering from, you know, like remex, you know, the contact that is not good. you know, the temporary crown came off, especially on a long weekend, they call you for emergency. So I was invited to the Pedersen sales event and I discovered the CEREC systems in 2005. And to me, I feel that that is the way to go. It's like a win-win situation for both dentists and for patients. First for us, I mean, it made my procedure a lot faster, more simplified. And I have all the control about contact, occlusion, margin. I print my own teeth. I mark my own margins. So that will make a lot more sense than sending it to the left. And I don't have to do temporary. So I don't have to worry about if my temporary is going to come off over a long weekend. So that's why I decided to jump into this trend. Right. So you're visiting faculty at SeaDocs. That's in Scottsdale, Arizona, right? Yes. Yeah, I've been there. It's a very nice training facility in a beautiful Scottsdale. Yep, I was there. And we actually did a live podcast from there at the Spear Center several years ago. So you're into CAD CAM dentistry, but some dentists are using digital dentistry, but they're just scanning and then they send the file to the lab. But it's important to you, obviously, to get it in one day, right? Because you obviate the need, as you explained, you don't need a temporary for the patient because they get their final. prosthesis the same day. Tell us about the blocks that you're using. What are the most common blocks that you like and why? When I first started my, you know, my cat cam dentistry in 2005, at that time, we only have four or five block available, you know, and so it's pretty easy for us back then to choose a block because basically you only have three or four to choose from. But today, there's so many different types of block. There's a ceramic block. There's a DCM disilicate block. There's a resin block. There's a zirconia block. And I understand that most of the doctors will go for a stronger block, which is zirconia. Zirconia not only in today's KKM dentistry. I mean, even for most of dentists, zirconia probably is the most used material in dentistry right now. But for me, I am more like a biomimetic dentistry type. So I prefer to choose something that is similar to what mother nature give it to us, like enamel and dentine, instead of choosing the strongest material, which is the 1000 megapascal zirconia. So Dr. Tang, you mentioned biomimetic. as an important factor, you're willing to obviate the strength of a material like zirconia for a different kind of material that's more conducive to the physical attributes and characteristics of natural tooth structure. So tell us about that. Yes. So to me, I think the definition of biomimetic dentistry is, you know, we should respect mother nature's creations. we were respecting and emulating the nature with the material that we have. For us, the teeth consists of the dentine, the enamel, and the DEJ. So my goal is to try to mimic that dentine, enamel, and DEJ, which is called... called by Dr. Pascal Magnier. I'm a big fan of him. So he called that dental trinity. So my goal is to try to repeat that dental trinity. So for me, dentine, I think the composite is more similar to dentine. And the enamel, this same disilicate is very, very, by all the physical property is closest to the enamel, which is this same disilicate. And the DEJ, we will use the composite cement to replace that DEJ. You know, cement will be using that composite cement to replace that DEJ. So talking about this same disilicate. So the reason why I like this same disilicate is because this same disilicate has very much the similar elastic modulus and also has similar the biaxial threshold strength, like enamel. You know, our enamel have about 80 elastic modulus, and this same disilicate about 95, and enamel is about 200 megapascal strands, and this same disilicate is about 300 to 500 megapascal strands. So that's why I prefer to use this same disilicate when I can for my CAD CAM dentistry. When you talk about modulus of elasticity, you're talking about the firmness or flexibility of the material. Flexibility. So lithium disilicate, you're saying, matches those physical characteristics of natural tooth structure better than some of the other materials, such as, I guess you're talking about zirconia, for example. Zirconia. And even the composite blocks, the resin block. Composite is the best to replace the dentine because it's closer or the physical, you know, the property is similar to the dentine. Now, what about those cases where you need strength? You have a patient that has an occlusal system where they're a Bruxer. It's important to have a material that's super strong. Does that override the notion that maybe the physical characteristics maybe are not as naturally representative of the tooth structure, but the strength is more important? Yes, I mean, I'm not saying that I will never use the cornea. I do use the cornea, but not as often as most of the dentists. So the case that I use the cornea is, first, when I don't have enough minimum thickness, enough clearance for my lesium disilicate, you know, then I will go for the cornea. And when I need to do a breach, then I will go for the cornea. Because again, in order to use a lesium disilicate as a breach, you might... you know the uh the strength of between the connectors and the uh zirconia will be a lot easier to get the strength of a connector size so i'm still using the cornea but i just don't use it as often as most of the dentists and for me i you know again as long as i can get that minimum thickness which is about a millimeter thickness for the same type this entire city kit i've been doing this for Long time, since 2005 and ever since the Emacs, the first lesm disilicate block available is Emacs. As long as you bond your lesm disilicate in, which is very, very important that you have to know how you treat your lesm disilicate for bonding, then as long as you can have that minimum thickness there, I think strength is not an issue. So you mentioned Emacs. What kind of blocks are you using in your office? Right now, I use, if I do need that strength, I use lithium disilicate, which is nowadays I'm using the DC block from GC. If I'm doing an inlay or onlay, I don't care much about that strength. I use hybrid block, which is a composite block. But, you know, again, for a full coverage crown, normally I will go with the GC DC block. Yeah, so that's Lisi, L-I-S-I from GC America. Why are you using that block in particular? Is there any particular reason that you like that particular material? Yes, I mean, GCDC block, it's a lithium disilicate block, of course. And the original, the first K-CAM block for the lithium disilicate, which is Emacs. But, you know, Emacs has all the good history and all the good benefit of using. But Emacs also has some disadvantage. We all know that the Emacs margin integrity is not as good. You know, once we mill the crown out, it's easy. Sometimes you will see those are cheap margins because, again, it's just because of the physical property of the Emacs. So the marginal integrity is not as good. And also that Emacs block. it's in purple stage because it's not fully crystallized. So after you milled it, it's in purple stage. You have to go into oven, go through a 14-minute oven cycle in order to make it crystallized, to be getting that tooth-colored shade and also to get that 350, or now they call it 500 megapascal strength. DC actually is a DC-DC block is a DC-DC block also, but because it's a technology, so it's a fully crystallized block. So the workflow is super simple. You just need to melt it, you polish it, and it's ready to be delivered. And because it's fully crystallized, so the margin is, you can make it super thin, and the margin is very, very smooth. And the strength of the Lisi block is the same strength you're getting with the typical Emacs, the ones that you actually have to put in the oven for 14 minutes? Based on the GC, you know, their information, it's 400 megapascal. And Emacs, right now, they claim that they have 500 megapascal strength. But when they first announced the Emacs back to more than 10 years ago, They say the strength of the Emacs is 300 something megapascal. So I think the composition, everything should be the same, but somehow they change it to 500. I don't have any testing facility in my small office, so I don't know. But I think they should be pretty much equal about the strength. So you're getting basically the same benefits of lithium disilicate in a block that you're milling chairside without... minutes of firing it up right you're going right to polish that is correct and also don't forget when you put into the oven 14 minutes when you first when they finish the crystallization cycle that crown is still super hot so you cannot touch it you have to wait until it cools down to touch it so it's not just a 14 minutes though so in your experience using lithium disilicate blocks specifically the lisi block from gc and you've been doing this for many years now, have you seen failures, fractures, debonding? What are you looking at as far as the failures compared to what you used to do with Emacs or other types of blocks? Yes, of course. I have to be honest with you. Definitely, I have some failure case, yes. But is it more than Emacs? Is it like, you know, really, really bad? Not at all. To me, I feel like as soon as I get, again, I've been using quite a lot of different material, but... long as you get that minimum thickness, one millimeter, and you actually treat your ceramic right, you actually burn it in, you treat your prep right, then to me, the GCDC is similar to Emix. Right. It's just more convenient for you. A lot more convenient, yes. Yeah, so tell us what the critical steps are to make the lithium disilicate in your office where you get the high success that you do. Yeah, of course, you know, the GCDC block or for all the Dism Dysilicate, you have to, to me, I bond my Dism Dysilicate in all the time, 99% of the time when I can. And you have to treat your Dism Dysilicate integral surface right. So once I finish the meaning, I take it out from the meaning machine. I do a try-in on patient's mouth. The reason, the main purpose of doing a try-in intra-orally is not to check the occlusion. I trust my occlusion from my KKM systems. So I don't check the occlusion before I actually bound it in. So my purpose is checking the marginal fit. If there's any open margin, how the margin fit. And also I check my proximal content strength. So as long as everything is right, then I actually go ahead and polish it. And if you like... Another benefit of using DC is if you really like, you can actually glaze it. So that will take about 11 minutes, depending on the glaze system that you use. So you can glaze it if you want to. But nowadays, normally, I just highly polish it. And it takes me about three to five minutes. Normally, about three minutes to polish it. And then this is the most critical. Step of the whole thing is to how you treat your lithium disilicate integral surface. So first, you will need to use 5% hydrofluoric acid to etch it for 20 seconds. And once you etch it, you have to fully rinse it with water. And then once you rinse it, you have to make sure your bonding surface is nice and clean. You can either use steam or use an ultrasonic bath. Personally, I like to use an ultrasonic bath, and I use an ultrasonic bath for about a minute. Use alcohol or with, you know, distilled water to clean it. And once you clean it, you take it out, you dry your surface, and then don't forget you have to use a silent. And for me, I use my, you know, G-Multi Primer as a silent. then you are ready to bind in your restorations. So tell us how you prep the tooth itself. It all depends. You know, sometimes I do IDS, sometimes I don't. I don't do IDS all the time, but, you know, for the... Simple, straightforward case. I will, of course, you put in your isolation, rubber dam or, you know, the isolate to get the isolations. Then I normally do etch-ins. You know, whatever bounding I'm using, I always use etch-ins. So either I do select edge or I do total edge. It all depends on the two. So let's say I was etched the two. If I do total edge, I was etched on the enamel first and then I go on to dentine. So I tried to etch my enamel for 30 seconds and then dentine for about 15 to 20 seconds. Then I completely rinse it off. And for a straight line workflow, I use the GCM1. That's their new cement. So it's a self-adhesive cement. They also come with a primer called AEP, Adhesive Enhanced Primer. So if I'm using the GCM1 cement, after I etch it, I rinse it dry, I clean it, then I apply the AEP, Adhesive Enhanced Primer. So I use AEP to rub on the surface, the prep surface, for 10 seconds. Then I dry it for 5 seconds. I load the cement. I sit my crown, I take cure it, I clean up the cement, then I fully cure it. That's how I do it for most of my case. It seems to be pretty successful because you've had a lot of years to see the outcomes of these cases, which have been very high, as we discussed earlier. So what would you tell, in closing, Dr. Tang, a new dentist who's getting into CAD CAM, let's say they're sitting at your class at CDOC or wherever you're teaching. What advice would you give them as a young dentist to say, this is something that you really have to keep an eye on to really ensure predictable, really solid outcomes of clinical success using CAD CAM? I think CAD CAM, you know, my daughter is in dental school right now also, you know, and I know that the school don't teach much about CAD CAM. So when you're first out of school, you get into CAD CAM, you had to learn slowly. it's it it do it slowly you don't want to just try and jump everything in everything k-cam you know and but you know for k-cam your plate will be different you know like if you you if you're doing a biomimetic dentistry you don't prep as aggressive you know there's a lot of difference right there but you want to start with you want to pick the right patient first the most important thing to pick the right patients right and pick the right right to to start with and then you start from the the easy step the inlay onlay then you move on to the full coverage crown then you move on to the multi-unit uh you know quadrants that's my advice yeah and what is the big difference in the prep design when using cat cam is it the fact that you're scanning and you want you know everything rounded very well no sharp edges yes that is correct i mean you know the uh because again for k-cam we do using a mini machine which is your restoration the integral surface is milled by a bird and all the meaning bird has a size of the diameter right so it's about a millimeter diameter so something that the new k-cam dentist don't understand this they look at they prep after they prep their teeth they have patient to bite down and they look like oh okay i got one millimeter clearance or i got 1.5 millimeter clearance but once you scan it but his prep is all sharp you know whole bunch of sharp edges so once you scan it you design and that wait a minute why i get that minimum thickness warning i don't get my one millimeter 1.5 millimeter why so something you have to understand is again all the restorations is milled that's why it's called mini machine it's milled by a bird and bird has a thickness so that if your your your prep is sharp then you will get we call it over mill by the mini machine so your prep had to be smooth had to be rounded that is a that is the key Dr. Tang, I think you covered it very well. I certainly appreciate your time on this podcast and we'll have you on again and you'll keep us updated on some of the things you're learning as you teach. Because I know when you teach at a facility and you get questions from students, you always learn new things yourself and then incorporate that back into your teaching. So you'll keep us updated on future podcasts. I really would appreciate that. Thank you. Thank you, 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.