SEPT 22ND 2023.pdf

So anyways, what we're going to do today is we're going to get started on ceramic restorations. All right. So far we've been just doing preparations for gold. You're aware of the benefit of gold. We've talked about it. You know, gold requires less reduction. Gold is longer lasting. Gold is kinder to...

So anyways, what we're going to do today is we're going to get started on ceramic restorations. All right. So far we've been just doing preparations for gold. You're aware of the benefit of gold. We've talked about it. You know, gold requires less reduction. Gold is longer lasting. Gold is kinder to the opposing teeth. Gold has a lot of advantages. Gold, also, for what it's worth, has certain disadvantages which you're no doubt aware of. It's gold colored. Most people don't want their teeth to be that color. It also, unfortunately, nowadays is terribly, terribly expensive. So gold is a problem for us because even if we want to use it, and even if a patient likes the idea of it and all its benefits, it's very hard for people to afford. It's very hard for dentist to afford to do it for people. So more typically, we're going to work with ceramic materials. Now in dentistry, there's going to be a wide range of ceramic materials available. We're going to go through some of these different ones through the course of the year. Today, though, we're going to start with porcelain fuzed to metal. Right? And it used to be sort of easy in dentistry when we talked about these things because so when I was in dental school, we had basically three choices. It was very easy. We either did gold. Or we did pause and fuze to metal. Or in rarer instances, we did what was called a porcelain jacket crown. It was an all ceramic crown, but it wasn't very strong. And frankly, you had to be very careful of using them. So back then it was real simple to treatment plan with your patients. You basically just had to decide if it was going to look like a tooth or not, and if it was going to look like tooth colored, it had to be PFM Pretty much. So treatment planning was a very simple thing. You're probably aware that nowadays in dentistry there is an enormous range of ceramic materials available to you. If you've opened your cell in the lab and as you did your administration step and opened it up, you probably saw that it gave you a choice of, I don't know, a couple dozen, maybe different things you could mill. The interesting thing, the challenge, let's say, is that to do any of these different materials, it requires a lot more knowledge from you than we used to have to have. It used to be pretty easy. All I had to know is how much reduction do I need for gold? How much reduction do I need for PFM? Make the preps accordingly. Bless you. So now when you start to consider bless you all these different materials, you have to sort of know what are the distinguishing characteristics of these? What are the requirements of them? Why would you choose one over another? It's actually a lot tougher. In some ways. It's nice to have choice in life, but in other ways, choices make your life more challenging. So anyways, as the year goes on, besides talking today about ports and fuze to metal through the course of our year, we're going to talk with you, myself and Jerry Dorado, the D two class all knows Jerry very well from Dental Anatomy Lab, the advanced standings. You'll get to know Jerry as time passes. He's your main fixed prosthetics technician, so Jerry will speak with us a couple of times during the year. So Jerry and I are going to cover the sort of range of these different ceramic materials to some extent, as much as we're able. But so there's going to be some choices as it is. I've already mentioned this to you before. Part of the reason we started with gold crowns, as you're aware, is that when you take the CDK exam, you're going to have to make a gold Crown Prep. Well, on the other preparation you're going to do for the CDK exam on the upper right quadrant, the bridge three by five is going to be for porcelain fuzed to metal. So we're certainly not going to discard that as a treatment modality. PFM still has its utility and there's times where it's better to use than perhaps some of the all ceramic materials. And so we're going to start with that. All right. So anyways, to do that, let's look at a few images. First, let's see if I can manage this. So what you can see, as I said, this is not ideal, obviously, but when you look you. Yes. This just doesn't project well on here. But over here, I think it's pretty sharp. If you look at these other screens, this is just an old gold on the bridge. It happened that this particular patient had this bridge start to fail and we replaced it with porcelain fuzed to metal. Now, the point of showing you this just which hopefully is sort of obvious if you look at this and you look at the staining that's been done, frankly, those look pretty much like teeth, don't they? Now, the point of saying that or showing you that is there is a tendency in dentistry and I don't know if any of you will be guilty of this in the course of your careers, but maybe it's a tendency all of us have to kind of want to jump on the latest and greatest thing, right? I mean, I'm using an iPhone. You know, every time Apple introduces a new iPhone, of course, I'm looking at it going, do I need to upgrade? And I mean, and most of you probably did that for years. You know, every two years you got a new iPhone. And somewhere along the line, we probably all of us said, you know what? Maybe I don't need a new one. This year. But there is certainly, for all of us, a tendency let's get the best and latest thing. Well, in dentistry, the latest and greatest and this is a bad bit of news for you is often a little bit unvetted. Our problem in dentistry is the dental manufacturers who push a lot of this, who are generating a lot of these new materials. In many cases, they don't have time to test it very well because they've got to be first to the market with it, which means that in some cases it's you as the dentist in your office. Who find out that a material actually doesn't work as well as thought. So in some ways, you've got to be a little careful about jumping on these things too fast. So the point here is, as much as some of the all ceramic materials are certainly beautiful, they certainly have various advantages to them. In many cases, they don't necessarily look more like teeth than good old fashioned porcelain fuzed to metal. The key is really about your technician. If you have a good technician, they can do wondrous things, whether it's with FM or Emax or zirconia. Any of these different materials can be well handled by the right technician. Now, for what it's worth, though, let's go on and look at this bridge as it was replaced. One of the things I want to highlight here, and I'll try to point out it here, although if you look on those other screens, as I said, it's a better view. Notice we kept our finish lines and therefore the margin of the bridge slightly, super gingival. Now, in this part of the mouth, that doesn't matter. You can see here. Well, it's hard to see here, but you can sort of see if you look at the other screens, a little dark line. That's where these crowns end. We're seeing a little bit of the metal that's underneath there, this far back in the mouth. It may not matter, but in the front of the mouth, it's more problematic. And that does point to one of the issues for us with porcelain fuzed metal. It's one of the challenges we'll face as we talked about earlier in the year when we're going to discuss the idea of our preparations and where we should put finish lines. You might recall I tried to stress to you that whenever possible, you want to stay away from the tissue. All right. If you can. It's healthier in every way. It works better if you can get away with it, whether it's gold, PFM, any of the all ceramic materials, you try to say, stay a little away from the tissue, you want to be super gingival. Everything about it from the preparation to the fit of the restoration, to the longevity of it, the patient's ability to clean it is better if you're super gingival. If though, you're going to stay super gingival with something where a margin might be visible. As you see here, one of the things you need to do as a dentist, you have to be very aware of this. You have to make sure your patients are aware in advance of what they're going to see, because the first thing any patient does when you put the restoration in their mouth and here we're using cheek retractors and mirrors to see this, but the first thing they're going to do is take the hand mirror that you hand them, or they might take their phone and turn it into a selfie view and they're going to pull their cheek aside and look at it. And if you didn't tell them that, they might see a little metal here, the first thing they're going to say to you is, why do I see a dark line? And now you're trying to explain it to them and why you did that. Whereas if before they ever get a chance to see this, you tell them. What I'd like to do for you is to keep the edge of your crown a little away from the tissue and you explain why it's better and say, Is that okay with you? If you pull your cheek aside, you'll see it. But realize that nobody on earth will ever see it but you, your dentist, and maybe your hygienist. Do any of you remember that old ad used to be for hair coloring? Only your hairdresser knows for sure. Are you all too young for that? Maybe it's possible. You know, there used to be an ad, I think it was for Clairol. They still make Clairol hair coloring, right? They don't make it anymore. I don't know what women used to color their hair at home. Do they not do that? I don't even know. It was ads for women and it was supposed to color your hair, hide the gray, you know, that kind of thing. And the tagline, which was actually a very clever one, was that only your hairdresser knew for sure. No one else could tell a good reason to buy it, Right? Well, with dentistry, this is the sort of thing where only your hygienist would know, right? No one would ever see it unless you go out of your way to show them as a patient. So you have to make sure they understand that. Now, just as by way of introduction, let's look at a couple other images real quick that are sort of interesting. This is a patient and this is just to sort of illustrate what you do with PFM. These are not porcelain fuzed metal. These are old restorations that were done somewhere. I won't tell you where in Eastern Europe quite a number of years ago, the patient immigrated to the United States. One of her goals in when she came here was to have her teeth fixed because she didn't like what she saw. Understandably, if you look at this, there's a couple of things to point out. If you look here, actually, I guess I can point this way. Notice the was really a mishandling of the occlusal plane Whenever the dentist did this sort of posterior reconstruction for the patient, they didn't correct any of the moved movement of the teeth, any of the misalignment in the occlusal plane. So these were made out of, in some cases, metal with acrylic facings and in other cases all metal on the upper. They used acrylic facings. So we're just going to run by here real quick just so you see what this looks like. But the point is that this patient wanted these changed and so came here at the time to be you and was at the time the posterior reconstruction was redone in porcelain fuzed to metal. And so we did what we could to fix things a little bit. If you look a little further, you'll see there are spots where we actually are going to still keep our finish lines where we can a little away from the tissue where it's not going to show. But if you look at the basic coloration of these crowns sort of shape, things like that, you know, they look quite natural. The color is good. The point is, porcelain fuzed to metal can actually achieve really nice esthetics. The only thing that was required for this patient is to change that composite then and she'll be all set and probably ask her to wear a night guard. Then finally, just another view. Here's just an anterior portion of to metal just sitting outside the mouth. Thing to notice is this is one of those materials where you have the ability because of how these are made, where the ceramic, the technician is going to build the material out of different ceramic powders, porcelain powders. So you have the ability to have incisal porcelain that's going to look translucent, like a natural tooth. You have body porcelains, you have a patient stents, you have a lot of things you can do to color these and make them look natural. And again, here's an example of a portion of Fuzed Metal bridge. Looking at it once again, by applying some staining, you can make something that, you know, color wise shape. Everything about it can look very, very natural. So that can be a really it can still be a good material for us and that would be the point. Now, the thing about it, though, if we're going to talk about this material, is to go back a step. Anytime we're going to crown a tooth we want to. Remind ourselves of why do we do these things? Anytime we're doing any dentistry for a patient, for that matter, not just crowns any anytime we're doing restorations, we're trying to sort of improve the long term prognosis of that tooth or of that part of the mouth or perhaps the patient's whole mouth in terms of their long term prognosis. So with that in mind, there is a point here where we start to run into it, Oh, geez, that isn't what we wanted to do. Here we go. This is one of the areas, though, where as you get into materials different than the gold, we come into some other challenges. Remember, one of the advantages of gold was it really allowed minimal tooth reduction. That's an advantage. The less tooth you cut away, the better for the tooth. It allowed us because it's, you know, inherently anesthetic. It allowed us to certainly, whenever possible, stay super gingival. There was no advantage in hiding the margin of a gold crown. That's also good for the health of the periodontal. So in many ways, Gold offered those advantages minimal reduction. You could stay away from the tissue. So you didn't. You sort of did what you could to protect the health of the pulp of the tooth. With the minimal reduction, you do what you could to protect the periodontal. And so those were advantages of gold. Our challenge, once we get into the ceramic materials is that in most all cases, they're going to require additional reduction. So that's adding threats to the long term health of the pulp of the tooth. And in many cases, especially with something like porcelain fuzed to metal, we may find us find ourselves when when esthetics become an issue, needing to hide finish lines and therefore hide margins of restorations so that they're more esthetic and that can affect the health of the periodontal. So we have to be aware of how these become a little bit more in conflict with some of our basic principles and our goals of these restorations. So as we look at that, let's consider what the needs of these materials are, because that's where this comes into play. So just to go forward with these images and this slide set actually, as you're seeing it today, will be available on the Blackboard Learn site. I had meant to post it up for you this morning, but unfortunately, without the Internet, I couldn't put it there. So if you look at the slide set that's present for this lecture, you'd see there's some subtle differences, but I'll I'll update it. I mean, it should have been updated already, but I couldn't do it anyways to get into what goes into and fuze to metal and what are the demands in terms of reduction of materials. What you can see here is that when you do these things, there's going to be a metal substructure. So if you say porcelain fuzed to metal, there is metal. So what gives these things that things their inherent strength is going to be a metal substructure. All right. That's going to be waxed up and cast to fit the tooth. And then because we have metal, one of the things we're going to have to do is hide the metal, because if you put porcelain on it, most porcelains are loosened. So you'd see the metal. That's a problem. So what we do is we put a layer of what's called opaque porcelain on there, and the opaque is designed to hide the metal, to create a juice. That's a patient. We'll have to deal with her later. So the the opaque porcelain is designed to hide the metal so you can't see it. And you choose depending on the color of the crown you want to have. As you're aware, we have different colored portions. We have different color composites, for that matter. So whatever shade we'd like it to be, we choose an appropriate opaque to hide the metal that's baked on. And I should let you know Jerry is going to actually, at some point during the year in a lecture, he'll go through the actual steps of how this is done. He'll show you kind of step by step how, you know, the the how they're waxed up and cast, how the porcelains are applied, just so you have a clearer sense. You know, we don't have time in dental education anymore for you to do your own, you know, pour some fuzed to metal or make these crowns yourself. It's useful to know those things. That way you can better talk to your technicians, but we don't have time for you to do that. But we can at least show you if you find yourself. I should mention this if you find yourself over the next couple of years interested in doing some of this, you kind of find the idea of dental technology interesting or appealing. You want a deeper understanding and sense of it. Talk to Jerry about it. He'll be happy to help you do some of these procedures yourself. You know, he'll he'll kind of let you help him do it. And you could gain a maybe a better sense of it, which is not a bad idea at all. So as it is, there's going to be the opaque porcelain. And then on top of it, we're going to apply varying layers of porcelain. The most basic way we might do it will apply a body porcelain, which is the basic color of the restoration, and then towards the occlusal or incisal part of it and incisal porcelain will start to have more translucence. And then if you like, depending on how far you want to go as a technician, you can mix in any number of different colors to subtly shade these things internally as opposed to just doing external staining. So, you know, as I said, Jerry will go over that with you. These are just a couple of diagrams of how these will work. Here's just another kind of diagram to sort of illustrate the point of how these might be arranged. So you'd see, you know, in the black here would be the metal substructure that's sort of yellow, would be the opaque porcelain, and then the other portions built over it. Just to give you a sense of it here, again, along the same way of looking at it, this would be what happens if you cut one of these in half. Right. You see, and just to show you better and this you'll find in the slide set once I'm able to update it for you, you know, there's a metal layer, there's opaque porcelain. Great. There's going to be in the opaque here, you can see as this sort of white material. And then on top of it is a body porcelain at the top, more translucent incisal. Right Now, the question for us is going to be, what are the demands of these materials? How thick do they have to be? Because how thick the materials have to be is going to determine how much reduction we have to make on our tooth to allow for that. You'll recall in our earliest discussion about our principles for Crown preparation, one of them had to do with what we described as structural durability. It had to do with making enough reduction on the tooth that the restoration could be made adequately thick. So it was appropriately strong and at the same time it wasn't necessarily over contoured because that's essential to us. If we over contour that creates other problems for us. So here's a couple of other diagrams that might get at this a little bit. Depending on the type of metal we're using, there's going to be differing demands for how much room we need for that metal. So if you're using like a very high noble alloy, we typically want a half millimeter of thickness for that metal to have adequate strength. When we're using a semi-precious alloy, it's going to be about 3/10 of a millimeter. When we use non precious, it could be as thin as one tenth of a millimeter, except that nobody wants to use non precious because it's frankly dangerous to work with for the technicians. Also, it makes a less good restoration. The more precious the alloy, typically the better the restoration can fit. And last and better how it can look. On top of it, we're going to have differing thickness. Is for these things. So the opaque needs to be about 2/10 to 3/10 of a millimeter thick to hide things. The body porcelain about 1 to 1.2 millimeters and then the insides of porcelain. If we want something that really is esthetic, can be as much as about 1.5mm. If you start to think about how much incisal you see on a natural tooth, that's where you come into those those numbers. Yes, good question. Is it something you. Yourself, the patient also, we have this different values, different metals that we can use on your family. So I think I get what you're asking. It's an important question. The question is, do we the term you say sell to the patient or do we at least discuss with the patient the choice of materials for what it's worth? No, not at least I don't. I'm not interested in putting in a non precious PFM. So essentially, if we're going to do PFM, we just do it. And what they get is the material that I and my technician choose to use. So this is more information for you to know these numbers, because what we're leading up to is an understanding of how much reduction we're going to need to accommodate these things. In terms of the choice of materials, this is one of those areas where I think you make the decision, you know, the dentist theoretically guiding the process along in consultation with your technician. I'm not sure if I've mentioned this before to you, but I think it's really important for any dentist to develop well to first find technicians that you have very high faith in. You know, you appreciate what they can do for you. They're knowledgeable, they're skillful, and that you are therefore able to work with them in a kind of consultative way. You can work together because there's times where the right solution in certain cases requires maybe more than just what's in your head. You know, sometimes you get whatever impressions it might be, send stuff off to the lab, have them set it all up, and then you can discuss it and try to figure out what's going to be the best choice of materials or how something might be designed. And so ideally, that's very, very valuable to you. You know, one of the mistakes dentists make at times and I think some dentists make, let's say, could be a tendency to say, well, all right, I was looking in this throwaway tabloid, you know, fake dental journal. And I found an ad from a lab located in China. And they'll including shipping, you know, they'll make a crown and turn it around in like four days despite overnight shipping. And it's only going to be $29. It's like, wow, this is going to be great because I'm going to make all this extra money instead of paying a local lab tech $200 to make it right. So you could do that. But a lot of what comes back might be garbage. I think personally you're better off finding that tech that you can talk to and work with that you actually respect as opposed to, you know, they're the cheapest you could possibly find and then work with them. But that's a choice for each dentist, you know. You have to decide what's right for you. That sort of answer? Yes. Good. Thanks for asking. So if we're going to talk about these requirements of materials, let's have a couple of the diagrams that kind of made, which I think we're going to try to get to this a little bit. So this is sort of trying to be a little diagram and cross section of what might be a molar. So again, going to these numbers, if we're using, say, a semi-precious metal, which here it b you when we do PFM, that's typically what we're going to use. So we're going to have something about 3/10 of a millimeter thick for the metal. So here in this sort of black line would be the metal. Then we're going to have our opaque porcelain, which is going to be somewhere in the 2/10 to 3/10 of a millimeter thickness here. It's this kind of, I don't know, lime green or whatever that color is. And then on top of it, we're going to have some body porcelain and ultimately some incisal porcelain. And these thicknesses are going to be a little bit of a range. But if you start to add this all up, what you would see back here and this is a lower molar, therefore the buckle cusp is going to be our functional cusp. If you start to add up how much thickness we need to have adequate esthetics and adequate strength in our material if we have 1.5mm here plus 0.3 plus 0.2, we need a minimum of two millimeters on our functional cusp. That be the same. Then in the other functional area, the central fossa on the non functional cusp on this lower molar, we might get away with something as thin as a millimeter there because the portion could be a little thinner. It's not going to be under function. So that's sort of one set of numbers you could look at now when we get to lab today. We are going to. Yes. We're getting there. Thanks for asking, but we're getting there. You can actually see the way it's drawn. This is a deep chamfer. So the way we're going to change our preparation is from the chamfer we've been making just because you kind of getting ahead of us. But that's all right. No, no, it's fine. You know, it's good to anticipate the where we've been making sort of a basic chamfer, what we're going to do, at least in the esthetic part of our preparation on the buckle surfaces, things like that, We're going to go into what would be more of a deep chamfer. This would be like our premolar that we're doing today. We're going to work on number 13 and we're going to look at a reduction ranging from about 1 to 1.2 millimeters on the buckle surface. And you're going to see something a little different up here. Recall that on a maxillary tooth, the functional cusp is going to be the lingual or palatal cusp. So we want our two millimeters there. So we have adequate strength, but we're actually going to also do two millimeters on the buckle cusps or maxillary teeth, at least as far back as the premolars. And the reason we're going to do that is in a lot of smiles, those premolars are somewhat of an esthetic zone. So we want a little extra room there because the real key to esthetics with porcelain fuzed to metal has to do with giving the technician room to work. If you give Jerry, who, as I say, most of you know, if you give Jerry some room to work, he can do beautiful, beautiful things. If you have very minimal reductions or inadequate reductions, there's limits to what he can achieve. There's just not enough room for him to generate esthetics in the space available. So with a quality technician, if you give them room, they can give you back beautiful things. And so when we work on our maxillary teeth, even the non functional cusps, at least as far back as the premolars, we're going to look for a little additional reduction. So these are going to be sort of our our numbers that we're going to work on today. Part of the reason these numbers vary on the buckle, because you may have noticed and this is not the world's greatest diagram, but, you know, if you look at a tooth and how the buckle surface has kind of a contour that moves in some ways, if we were doing like sort of a 1.2mm here, what we're going to find is that the actual reduction as we go higher up because the contour of the tooth is actually going to be a little greater. So that's where we describe a sort of range. It's not that we're trying to make it obscure to you. So. In talking about finish lines, though, because that subject came up. Let me kind of go ahead, because in our material here, that was sort of our next thing to consider. So let's go forward in our slides and just to go back and we'll talk about finish lines for a moment, because that was a really good question, anticipating where we're going with this. So here you see in cross section what would be like a feather edge finish line. But when you talk about something like porcelain fuzed metal, what you would see happen here is that if you have a feather edge, you can see here's the tooth. Oops. Here's the tooth. So if you see the feather edge, if you're going to have that porcelain covering the metal so you hide the metal, you're going to end up with over contour. You can see this is over contoured here. As soon as you would start to polish this back. To get a proper contour. The only way to do that is going to show a metal collar. That's the only way you could have a proper contour with that sort of finish line. If you go into stuff like a bevel because we talked about the range of finish lines earlier in the course, if you're going to have a proper contour, you're going to show metal. Here's another diagram of a fairly steep bevel. And you can see in yellow what would be the metal if we're going to have a proper contour here. So this contour. Why is this? All right. So. Hmm. It's weird. So if you have a proper contour, though, what we're going to see is going to be a metal collar, which obviously we'd like to minimize. There's another way to visualize this and just have these different illustrations. There's different ways for hopefully you to see this. This is using our kind of reduction stance that you've been using, right? So here's a prep. You can see it has a bevel on it if you notice in this little corner. Right. There's very, very little space. If you have proper emergence profile, proper contour to your crown, you're going to have a metal collar, right? So here would be another example of the same thing. If you look, there's no room there to put porcelain over the metal substructure. You're going to show metal. By contrast, this might help to see this. Here is a chamfer and a somewhat slightly deep in chamfer, but not that deep. And there's more room. So you could imagine as you get to that edge of the margin, you can thin the metal and you can minimize the amount of metal that might show. And so what we're going to do, as was asked, is we're going to get to finish lines for what we're doing here, where we're going to be using not just a regular chamfer, but we're going to create a deep chamfer. We're not going to use a shoulder. And the reason we're not and this is just an example of a shoulder and you can a shoulder can work fine. We're not using shoulders mostly because a lot of what you're going to do, not just here at be You, but in the future, a lot of what you're going to do are going to be all ceramic restorations. Shoulders have sharp line angles. One of the places where things generate cracks are at sharp line angles. So we're going to try to avoid sharp line angles when we can in the hope of not generating stresses in our restorations. With PFM, it wouldn't matter. The metal's not going to care about that stress. But if you're doing all ceramic, we'd rather avoid these sharp line angles. So we're going to stress in our class that the preparations you do when you're involved with porcelain are what we'll describe as a deep chamfer. And I'll show you a couple of diagrams of that in just a moment. Just to proceed here before we look at that, just to drop more here would be the idea of doing a metal substructure, as you see in yellow, but shortening the metal before it actually gets to the very end of the finish line so that the margin itself ends up in porcelain. So this is what would be called a porcelain, but joint margin. This is one of the things we did for many years before we had really good choices of all ceramic materials as a way to make more esthetic margins. This requires much greater skill from the dental technician. So it was in some respects a little bit challenging from in that way. So let's jump over here for a bit just to look at something else, because we were talking about how we're going to modify our finish line design from what we've been doing. So what we'd been doing was kind of a basic chamfer, and that's what you've done so far in the class. What we're going to do when we want to do porcelain is we need to need to create more reduction both in the finish line area as well as axially. And so what we're going to do is create essentially a deeper chamfer. We're just going to go a little deeper. We might choose a larger diamond to create this shape. We're going to use our round ended tapered diamond the same as we've been using, but essentially using a larger one. And in that way try to generate this other shape. Now, there are a couple of things I want to stress to you about this. One would be our goal with our finish line is we'd like it to approximate 90 degrees at the finish line itself. Now, I'm not necessarily looking for you to do 90 degrees to the long axis of the prep, but more interested in the idea of 90 degrees to the surface of the tooth. So if the external surface of the tooth angles a little bit because the root is thinning, you'd rather that this is the 90 degrees you see and this is a way you avoid the risk of unsupported enamel there. Which is one of the great challenges for us, of course. A couple of the diagrams related to these things of stuff we've looked at, and then we'll go on to a couple other slides and stuff. This would be the idea of our regular chamfer in blue, except that if we have a proper contour, proper emergence profile for our restoration, you could see that the metal thinned down as much as possible is going to show a wider collar. Whereas if you have a deeper chamfer, as you thin that down, you can visually create what looks like a thinner line of metal. So it's an advantage because if we were going to hide this under the tissue, you don't have to hide it as deep. So that would be where we try to change our preparation this way. A couple other diagrams related to this. That I've created. So this would be the idea of our deep chamfer trying to thin the metal quite a lot. As a reminder, it's easy enough to kind of fake things however you'd like in a drawing. I'm not sure we could get away realistically with the metal this thin, but I can draw it so I can cheat. And this would represent a portion but joint where our metal is ending here along the chamfer. And we have this area that can be ceramic. Now, I should add one thing about PFM that's important to be aware of. The same as we spoke about gold being a material that's disappearing in dentistry for a range of reasons, one of which is cost. One of the challenges with PFM is to some extent it might be facing the same pressures, even if we're using, say, just a semi-precious alloy. The cost of employing that metal compared to something that's all ceramic can be significantly higher. It's much more work to create a porcelain fuzed metal crown in the laboratory than it is to say have the machine mill a crown or than it is for the technician to perhaps wax up and press an Emacs crown. It's much more work and the materials that go into it are more expensive to do porcelain fuzed to metal. So increasingly it's under the same kind of economic pressure, the same money pressure, because if you're debating a restoration for your patient as the dentist and it's a fair question always about how do you choose metals, how do you choose anything? You know, you have to keep the lights on. You have to pay your staff, you have to keep your office open. You're a small business. Most of us in dentistry, if you insist on, you know, doing all gold for people and you don't want to charge an upcharge for the metal before you know it, you're in trouble. Arguably the same is true with porcelain fuzed to metal. So even if you don't choose to send your lab work to China for $29. The cost of having your local technician. You're very good local technician make you a crown in, say, full contour, zirconia versus porcelain fuzed metal. The PFM is going to be much, much more expensive. And so you might find yourselves understandably drawn to, say, choosing a good technician, you know, paying for the quality work, and yet finding that PFM may not have as much of a place in your practice as it could. And yet there are still places where it's valuable. When Jerry speaks to you later in the year, one of the things he'll stress is very often what he sees here at school is, especially with implant restorations, we'll do them in all ceramic when they as he'll say it, when they fail, he remakes them as PFM because the metal doesn't have quite the ability to fracture in the way ceramics do. That's one of the challenges of ceramics that you have to be aware of. Ceramics can crack right? Porcelain cracks. You have all probably eaten on. China plates. Right. And some of them, if you look, have little chips on the edges, ceramics, chip. And so even our best ceramics, even things like our zirconia can break just in the last couple of weeks. For the second time ever in my practice, I saw someone come in with a fractured zirconia crown. And for what it's worth, when these were first being introduced, one of the labs in California, one of the big labs, the way they introduced full contour zirconia was by sending crowns to all the dental offices in America. And what it said in it was try to break this. You know, try to break this. And my partner in the office who's, I guess literal, he took it out back, took a hammer and started trying to smash it. And the interesting thing is it didn't break. Couldn't break it with a hammer. So if you could break it with a hammer and yet patients manage to break it in their mouth, which they do, they're they're amazing what patients can do. But so any ceramic can break. So you have to be aware of that. And that's one of those things where gold can, you know. But anyways, let's just cover a couple of the things quickly before we're done. Just to go back to a couple of the diagrams and then a few other slides real fast and then we'll be done today. You recall when you did Full Gold Crowns, we were saying if you look down on it, actually we wanted the same axial reduction all the way around, right? It was sort of easy to judge if your axial reduction was correct. When you do PFM, very often what you can do if you're interested in, say, the buckle surface, is more of an esthetic zone, you might go deeper there. You could do a little less reduction on the lingual if you're trying to minimize tooth reductions. So it can be a little trickier to judge if you've done it just right. A final thing in these diagrams to show you is that question of. Unsupported in ammo. So as we talk about if you're going to go into a deeper chamfer, you have to go deeper into the tooth with your round ended tapered diamond. And as you do that, you have to try to do it without going deeper gingerly because when you do and that can easily happen, that's where you generate the sort of unsupported lips of enamel. Now let's go back to a last few slides. If I can get this open and we will. Oops. Please focus. Where's our autofocus? This a weird. This is misbehaving. It was working great before, wasn't it? Let's try something else. Let's shut it off. Turn it back on. Okay, look, now it's working. But now I've got to get this straight. Okay? So let's just show you a couple other things here, and then we'll be set here. All right. So here's a case. This is with the lip retractor, but this is a patient who had had basically a lot of tissue and bone loss here. So the patient lost some teeth. They lost a lot of tissue and bone. The oral surgeon who was placing implants here grafted it repeatedly could not regrow bone and tissue. The patient was not happy with the esthetics. The teeth looked long to her because what patients do, as I said, is they take their finger and they pull their cheek aside, Look, teeth look too long. That was a problem. So what was done just to show you and this is one of the things you can do with PFM is we picked a shade and not just a shade for the tooth, but we took out a sample here you can see, of a tooth color, I mean, a tissue colored ceramic. So if you work with a technician who is good at this and comfortable with this, they can give you examples, little shade tabs essentially of tooth colored ceramics and so and not tooth colored, tissue colored excuse me, tissue colored ceramics. And so what you can do is go through those the same as you do your shade tabs for tooth color. You can do that with tissue. You can see that looks like a pretty nice match. This goes to the lab. They can make you a couple of crowns here, right? With some tissue. This goes back to the mouth now and we go to put it in. And if you retract the lip, it looks much more natural. The teeth don't look unnaturally long. It doesn't look like they have some terrible periodontal disease patients thrilled. Now, the weird thing about this, of course, is this is the patient smile. If the patient didn't bother to pull their lip aside, they would never know. The world will never see it. But the patient, just knowing that the teeth would look long if anyone ever somehow stuck their head up in there, that would be a problem to them. Every patient has their own kind of priorities or ways they conceptualize these things. And you have to be you have to try to root that out and deal with it. Now, this is something you might enjoy the look of. Right. Now. You might notice if you're a particularly keen observer of something that looks out of place here, you probably, you know, now you guys are sort of new at dentistry, so you might have trouble finding this, but but it's to me it's actually it's a sad thing, but it's sort of funny. We can enjoy it ourselves. So this patient had gone to a dentist kind of in the neighborhood not too far from where I'm at. And this guy was always a terrible dentist. And then when implants came along, he became an implant ologist at which he was terrible as well. And but it was a way to reinvent his badness. And so what he did, what he did is, sadly enough, just so you know, where this is, it's not laying in the it's not in the canal. What he did, the dentist drilled a hole through the mandible and place the implant and it came through right through the mandible. It's laying on the floor of the patient's mouth, in the soft tissue, on the lingual of the mandible. So the way this came to me, these bridges weren't here. Of course, these are porcelain fuzed metal, as you can see. You can always tell porcelain fuzed to metal because you can see the kind of brighter metal substructure in the porcelain around it. But anyways, the patient came to me at that point to have bridges done because he kind of lost faith in implants. What happened was the a local periodontal office saw him after the other dentist popped the implant through into the floor of his mouth. They looked at it and said, Well, we don't know. We can't. You know, there's nothing we can do with this. They sent him to Mass General where the surgeons there looked at it and said, you know what? It's not going to cause any problems for anybody. We're just going to leave it lay there in the floor of the mouth in the soft tissue. And so that's how that went, for what it's worth, just to proceed. What ended up happening then is the patient had been wearing an upper denture forever and had very, very little bone left. But a surgeon at mass senior or a mass general, I guess one of the oral surgeons, they did manage to place a series of implants because the patient at that point wanted to get out of his denture. And just to show you what was done real quickly, there was restoration made, porcelain, fuzed metal on those. And just to go through the steps. So you have a sense of how this was done. This is his old denture. This is what he looked like. Now, I wouldn't say this is the most esthetic looking denture in the world, but that's what the patient looked like. If you have a patient who looks like whatever they look like and they want to keep looking like it, you make models of whatever it was, whether it's directly in the mouth or in this case, a denture. You take the model, right? You pass that information along to your technician. You know, the way this was done and this is done quite a number of years ago, this was with a series of custom abutments. There was a laboratory process, temporary, made later in the course, we'll talk about process temporaries and when we use them and why we use them. You can see here this was the model of his denture, right? He has a little bit of open occlusion there, doesn't he? The interiors don't touch. So the process temporary does the same thing. Just so you see, this is what worked in his mouth for decades. This is what we generated for him. And even the process temporary is made with some pink acrylic. In this case, a metal substructure was generated by the lab and then porcelain applied. Right. And you can see this basically looks like his old denture. He's happy. Good case. Any time the patient is happy, it's a good case. Final thing, this is a portion of fuzed metal involving an implant, this anterior tooth. This is just so you can see. This is where the implant out of the mouth. Here's the implant buried down there in the laboratory. A soft tissue model is made, right? This is screw retained. And then when the restoration is placed in the mouth, you can just see it's sealed up in this case with a temporary material. Eventually, when we know that it's working well, you seal it with something more permanent, like resin. But these are things where. Of course, infused metals especially good. The metal doesn't break easily, it doesn't fatigue nearly as easily as ceramics. So to do this particular thing in all ceramic, it can be done, but the risks are a little higher. Okay. And that's one of the things Jerry will talk to you about. Any questions before we stop right now? All right. Sorry we couldn't take attendance today, but without the Internet, it didn't work. So anyways, for the A's class, we'll see you guys over there in a few minutes. We'll do a demo, get started, see the details this afternoon.