01032024.docx

So let's start talking about major connectors. The definition, uh, part of the framework which unites its components and permit stress distribution among them in order to distribute stress. The major connector must be rigid, must be rigid. Pushing one object against another object will distribute st...

So let's start talking about major connectors. The definition, uh, part of the framework which unites its components and permit stress distribution among them in order to distribute stress. The major connector must be rigid, must be rigid. Pushing one object against another object will distribute stress if both objects are rigid. If one object is flexible, it will absorb. The pushing action and it will not, um, it will not allow that object to be moved. Major connectors must be rigid to distribute stress. So I'm going to give you a preview of the four maxillary major connectors that we typically use. Now there's lots of shapes and um, depending on the distribution of missing teeth, but we have four major categories of major connectors on the maxillary arch and two categories of major connectors on the mandibular arch. Some of you may have heard, um, different terminology, different names of these major connectors. Um, and if so, it shouldn't be much of a departure for, uh, for you, uh, from these names. But, um, I will review the terminology with you now. So this is, uh, an AP or anterior posterior palatal barres. First I'm going to show you what they look like. And then I will review, uh, major connector by major connector as far as their, um, highlights. So this is the AP palatal bars. This is a major connector called the broad palatal strap. So you can see, um, beginning to see highlight differences between the two. Um, this is a major connector called full palatal coverage. And you'll see in just a minute that it will cover the full palate. Part of it is going to be metal and part of it is going to be acrylic. And this is a horseshoe, the shape of a horseshoe. So those are the four maxillary major connectors, um, give or take slight design movements depending on the distribution of missing teeth on the mandibular arch. We either have a lingual bar which is a simple bar, um, below the mandibular anterior teeth, or a lingual blanket, which covers the mandibular most of the mandibular anterior teeth. And you'll see why in just a minute. Okay. Let's start with the anterior posterior palatal bars. Here is again an example. And here is a graphic of the basic design. It is the most commonly used maxillary major connector. Um. By default it is the most rigid because of the anterior and posterior bar. The anterior bar is broader but thinner in thickness. Um, it causes between the rouge in the anterior so it doesn't cut across the rouge, but you'll usually see it very undulated. So it courses right through the rouge. Um, it is brought back six mil, a minimum of six millimeters from the gingival margins of the anterior teeth. So it respects the anterior teeth and it helps for speech. Okay. So we don't want it up in the anterior region. We want to bring it back at least six millimeters to help with speech. The posterior bar is narrower but thicker for rigidity. Um. In cross-section it is half teardrop shaped. It is thickest at the posterior, so this portion is the posterior of the posterior bar and thinnest in the anterior. The posterior bar is no farther posterior than the junction of the hard and soft palate. Okay, so it must be anterior to that junction of the hard and soft palate. There are no right angles between the bars. So basically you have an anterior bar, a posterior bar, and kind of like a circle or, or a rounded off square in between the two bars. The bars must be perpendicular to the median suture, so it crosses the palate at right angles. Okay, it doesn't usually cross the palate on a diagonal. And that's basically for symmetry and for patient comfort. OOP. Any questions for the AP palatal bar. Okay. The broad palatal strap. Um, the broad palatal strap. Depending on the missing teeth, if they're in the anterior. Um. May cause issues because the broad palatal strap is thinner, is only one piece of metal, and it goes from side to side. It goes from one side of the arch to the other, but there's only one piece of metal, and so it needs to be made thicker for rigidity. That thickness may cause speech issues. Okay, so the thickness for rigidity may cause speech problems, but basically it is one piece of metal. The anterior border. We want to. We want to keep as far posterior as possible. So again, depending on how many teeth are missing we want to pull it back again is at least six millimeters from the free gingival margin of the anterior teeth. The posterior border must cross the median suture perpendicular again for patient comfort. Um, we use a broad palatal strap when only a few teeth are missing. Usually a single finger width apart. Um, this diagram is a better diagram than this particular, um, broad palatal strap. But here we only have a single tooth on one side and a single tooth on the other, but we couldn't have made it any thinner because it would have been way too thin in the anterior, and way too small for the patient to keep it in their mouth without, God forbid, having that come out and the patient aspirated. So any questions about the broad palatal strat? Okay. Full palatal coverage. So the full palatal coverage is a major connector that is used in one specific application only when the patient is a Kennedy class one on the maxillary arch. So if a patient has a bilateral distal extension on the maxillary arch, that's when we use full palatal coverage because it enables us. You see this dotted line. This dotted line represents acrylic. So if we look down here you can see here's the metal that allows the meshwork to be placed in the posterior area or in the finish line. We're going to talk about finish lines in a minute. Um and then the acrylic gets processed um distal to that. So here's the acrylic that will hold the teeth. And in addition to that, think of the posterior aspect as a complete denture. And what we can incorporate into the posterior aspect is a posterior palatal seal. So it provides additional support and additional stability to this partial denture where the patient only has a very few remaining teeth left. And it is difficult to stabilize this upper denture for the patient. Okay, so full palatal coverage is the major connector of choice in a maxillary kennedi class one. It can include a post stamp. It can cover Tori. If there's a Taurus present, we can cover it with acrylic. And we're going to talk about Tory on both the maxillary and mandibular arches in just a minute. Um, we can have. If there's no Taurus present, we can actually design this major connector in all metal. But we don't typically do that now. Only because. Um, placing acrylic on here allows it to be a lot more adjustable than having an all metal pallet. Um, if. And the reason why we've always we've typically done an all metal palette is that it's a good thermal conductor. So you might think, well, why would we want to put a partial denture in there that's all metal as opposed to acrylic. Um, number one, it is a good thermal conductor. But number two, um, a partial denture that's that has a metal pallet can be made much thinner than a partial denture with an acrylic pallet because you need a certain amount of thickness for acrylic so that it doesn't break. Metal is not adjustable. You can't put a post dam in a metal pallet and it is bulkier than acrylic. Okay, so so far. Any questions on full palatal coverage? Okay. The horseshoe. The horseshoe is, um, again an isolated, uh, major connector that's used in only certain circumstances, um, that its present. A horseshoe has its issues where it will rotate horizontally if not stabilized in all four areas with teeth. Okay. So it really needs to be a Kennedy class three modification one or a Kennedy class three. Okay. So you really need four teeth in order to hold that horseshoe in place. A situation like this where we have a Kennedy class two or even a one, is not a good example of utilizing a horseshoe because it will fishtail and it's a very unstable major connector. It's best with tooth board partials. It's best with many guide planes. Um, again, in this situation, it needs to be made thicker because the major connector is so much smaller than the other major connectors that we've talked about. So if it's thicker and it's farther anterior, um, the thickness for rigidity may cause speech problems. Um, it's used typically. Where a patient might have an inoperable maxillary torus at the junction of the hard and soft pallets. So if we can't bring an AP palatal bar into this situation and there's a Taurus in this area, we may have to do some kind of a modified horseshoe for the patient. We call it the gambler's last resort. So, you know, just like when we're designing a maxillary denture, we want to use as much surface area as possible to increase adhesion, to increase cohesion, to increase the retention. The same thing when you're thinking about a major connector for a partial denture. You want to maximize the surface area in order to increase again adhesion, cohesion, and the stability of the partial denture. The smaller the major connector, the less stable it's going to be for the patient. Okay, now we're on the lower. The most common major connector for the mandibular arch is a lingual bar, and we basically default to the lingual bar unless certain conditions are present. So let's look at the lingual bar. It is relieved from the tissue. So unlike the maxillary major connector, which sits directly onto the palate, this lingual bar needs to be relieved from the tissue because the tissue is very fragile and movable. Um, it is half tear shaped. So this is the cross section of the lingual bar with its major bulk inferiorly. Um, the superior margin is three millimeters from the free gingival margin of the mandibular anterior teeth. The bar is three millimeters wide at minimum. Therefore, if you take a look at the overall requirements for dimensions, it requires a fold a lingual fold depth of at least six millimeters during tongue movement. So when you're assessing a patient for a mandibular major connector, what we're going to do is we're going to ask the patient to stick their tongue out. And we're going to look with either a mirror or a probe, and we're going to see what happens to the fold during the patient's tongue movement. And if the patient still has six millimeters of depth in the lingual fold, then usually the lingual bar is adequate for the major connector. Questions. Okay. Lingual blanket. So its indications include the shallow lingual floor. So if a patient doesn't have six millimeters that's our first consideration to use a lingual blanket if a patient has a high lingual freedom. We're going to need to use a blanket, um, inoperable lingual Tory. So some patients have to try. And we're going to learn that the first, um, uh, treatment of choice on the mandibular arch is Taurus removal. Because we typically can't get around mandibular Tory even to design a lingual blanket. Um, but, um, if for some reason we can. And if for some reason it is contraindicated to remove the patient's lingual Tory, then we might be able to use a lingual blanket. Um, some of you know this, uh, uh, particular major connector as a lingual apron. So that would be an alternative, um, for blanket. If the patient has a previous lingual blanket, um, then you might want to use similar. And the reason why I say that is, uh, coming up in just a minute. Um, increased distribution of occlusal load. So if, um, if the lower arch of teeth are weak, if the patient is missing certain key teeth like a lower canine, and the patient has, for example, only 4 or 5 mandibular anterior teeth remaining. So patient has, you know, tooth numbers 22 to 25 and is missing, um, the other canine. And so you want to increase support. You might consider using a, a lingual blanket questionable prognosis of the lower incisors. So here we have a lingual blanket. And let's say those lower incisors are have a questionable prognosis a fair prognosis. And we might wind up losing those teeth over time. The lingual blanket allows us, um, to have a backing of metal on which we can eventually add a tooth should the patient lose those lower teeth in the process without having to recreate a new framework. Splinting weak teeth so it does help to splint weak teeth, um, in the process. The blanket itself contacts the teeth, but again, not the gingiva. So, um, the, the portion of the blanket that sits over the gingiva, over the mucosa, it will be relieved, but it will the superior portion will contact the teeth in such a way that it will require rest seats in order to do so. So it requires rest seats on all the lower anterior teeth, because it will need to redirect the forces down the long axis of the tooth. You don't want to create a lingual blanket that pushes against the teeth, because that will not help on weak teeth or teeth that require splinting. But if we create rest seats, then that will increase the occlusal support and redirect the occlusal load. Okay. Any questions on that? Okay. The inferior border again must be at a depth compatible with tongue movement. So once again we're going to need to have the patient lift their tongue, stick it out of their mouth. We have to see how far that tongue movement goes and check the depth of the lingual fold. Once we do that, we'll be able to design the inferior border and then move up again six millimeters onto the tooth. So the relationship to the soft tissue, the maxillary contacts the tissue, contacts the palate. The mandibular is relieved from the tissue. This is due to the differences of tissue type and tissue movement. Um, on the maxillary arch. We actually also have one additional feature, and that is we score a bead, um, into the cast in certain areas of the major connector to act almost like a teeny tiny little post dam in certain areas in order to create an additional seal of the maxillary major connector into the palate. It's not very deep. It's just like a scratch line. Um, in order to get some additional, um, uh, surface area, um, contact of the maxillary major connector. So this bead ensures additional contact and you can see, um, on the major connector. That bead that's appearing. You'll see the bead in most every area except for where the finish line is, the finish line being the junction of the metal of the major connector, and where the acrylic is now going to join, um, the framework. On the mandibular arch. The mandibular arch has wax relief as a spacer so as the framework is being produced. Wax is being added either manually or if it's being done digitally. A virtual wax layer is added before the, um, the portion of the framework which is designed on top of the wax so that you have this layer or a spacer, just like we created spacers when we're doing custom trays for our impressions. And there's a tiny little space here so that when it goes to place our rests in the rest seats, we'll hold it exclusively so that it doesn't go farther into the gingiva, and then the space will remain, um, so that it doesn't touch the mucosa. Okay. Any questions? All right now major connectors. And today. So here's a maxillary peduncle rated Taurus usually a Taurus Tori even on the maxilla. We recommend having removed um, certainly something as large as this, especially at the junction of hard and soft tissue is a real challenge to design, uh, to design a removable restoration, a Cecil Taurus. You can definitely get a restoration over it. And it's typically non interfering on the mandibular either peduncle or sessile. Um these Tori we recommend to have removed. Notice how close this is to the free gingival margin. It's almost impossible to get a lingual bar certainly or even a blanket up and over it because those major connectors are going to be sitting horizontal right over this Taurus. And it's over time with tooth movement. And movement of the partial. It will eventually settle back down into the Taurus and create some issues. So those are removed before we move forward with the partials. Now, good thing is, when you take a look at the categories of major connectors, the AP palatal bar being the most common of the maxillary major connector, the hole in the center of the AP palatal bar. What we try to do is if a patient does have a maxillary taurus is we try to design those bars around the Taurus. So on the maxillary arch. As we said, the treatment of choice is if it's sessile, we try to keep that Taurus but design around the Taurus. So even if there's a maxillary Taurus here, we don't say, okay, we're going to do a horseshoe. If the treatment of choice is, um, an AP palatal bar, then we're going to design around it and put the Taurus into where the whole of the anterior and posterior bars are. If the patient has very few missing teeth, let's see if we can try to put the broad palatal strap either anterior or posterior to it, depending on where the teeth are missing for full paddle. For full palatal coverage, will try to curve the metal portion anterior to the Taurus and design the acrylic over um, the Taurus so that it's adjustable. And again. Jagger's last resort. Taurus. Last resort. If we can't come up with any other option. And the Taurus is either way too big to design a posterior bar wherever the Taurus is, then we might consider using a horseshoe okay on the mandible. Treatment of choice remove the Taurus and design with a lingual bar. Hey, it usually never works out where we're going to say, well, we're going to try. We're going to try the lingual blanket first. And you know, by the time you're doing the trying. Um, by the time you do the impression, get the framework back, do the trick. And it's it's pretty miserable. Um, especially with Tory that this large. And I've got some, uh. Pictures coming up of trying to do a try and over that large Cecil Taurus. And it doesn't work out. Metal must never cover a Taurus. So again, on the maxillary arch, choose the major connector of choice design around it. So remember maxillary most common AP palatal bars, unless it's a maxillary kennedi class one. And then we use. What? Full palatal coverage. Exactly. So this is this is what we try to do with this, with this Taurus. We tried to do a. This is kind of a modified lingual blanket, but, you know, by the time this curves around and curves up and over and then we had to transition into the acrylic, it was pretty miserable. Um, we went all the way to altered cast impression. You don't know what that is yet, but we'll talk about it. Um, and we wound up scrapping this ad insertion because the patient was pretty miserable, and we wound up removing the torus, so. Mandibular tau, I generally interfere with the inferior border of the partial. Whether it's at insertion or, you know, somewhere down the road, it it does pretty quickly. Um, in, uh, have have issues. And they generally require removal. Um, other problems with lower major connectors when we're surveying, and we haven't gotten to this point yet. You know, we're pretty much, uh, focused on undercuts and guide planes and receipts and survey lines and things like that. But one of the things that we're going to have you do when we start our survey and design seminars is we're going to be giving you some real casts in real world, um, cases. And, you know, some of our real world cases have mandibular teeth that are tip lingual and sort of overhang into lingual vestibules. And when that happens, we have to be very mindful of the surveys in this area, because if we have teeth that are tilted into the lingual vestibule, we have to be mindful of the lingual major connectors, because if the teeth are tipped, then the lingual major connector just like approach arms from the buckle, cannot be brought any closer to the tissue. And so lingual major connectors can also be a problem with lingual tip teeth. Um, so we're going to be looking at a case or two with that situation. So not only do we have to survey the buckle for class balms, we also have to survey the lingual for major connectors and undercuts. Um so keep and be very mindful of that. Any questions so far? Okay. Finish lines. Finish lines are basically a butt joint. 90 degrees at the junction of metal and acrylic where the major connector meets the denture base, preventing leakage at their interface. So if you have for example, here's the major connector, there's your meshwork where the denture base is going to. Now join the major connector. This is a diagram of the cross section where you have your mesh work. Um, coming out of this is your major connector. Here's your mesh work. Both above and below the meshwork are finish lines because your acrylic needs to surround the meshwork okay. Both inferior and superior to the meshwork okay. So we have an external and an internal finish line. And each one is handled slightly differently. Okay. The external finish line is created from, in an analog way, a plastic pattern. The internal finish line is created from that wax spacer that you just saw a few slides back. So the external finish line right here is what you can see. This line, um, that's on the outside or the tongue side of the partial denture. Um, and this is obviously without acrylic. Here's the internal finish line now with acrylic added to it. Okay. And here's our diagram again. Um. So now the other component of the framework are made up of single tooth spaces. So let's talk about those for just a minute. Um, single tooth spaces, whether it's an anterior tooth here or a part of a posterior tooth here, have less surface area to chemically bond to the denture base. Okay, so if there's less surface area, it's the tooth itself is about the same, um, material that the denture base is, is from. So it may require additional mechanical retention in order to keep it connected to the partial denture. Um, it may require additional mechanical reinforcement in order to with withstand the occlusal forces. So in the anterior we have an item called a steals facing, a steals facing replaces a single missing anterior tooth, and a little bit of the bone that might be missing. If so. It can also replace multiple missing anterior teeth if there's insufficient occlusal clearance. So in other words, if there's an excessive amount of bone and we don't want to have a flange in this area, a thick acrylic flange, um, we might want to just attach the tooth to the framework itself with a metal backing. And so we can have multiple steels facings. In the posterior, it will replace a single missing posterior tooth where additional mechanical retention is required. Again, because of that single tooth trying to bond to the denture base, it may not make a good bond, but if it has some additional mechanical retention, it might work out better. So let's take a look at the different situations here. We have a missing anterior tooth a couple of here's an anterior and posterior. Here we have a lot of bone and consecutive anterior teeth missing okay. And we might not just want to put a flange here but individual teeth. So it looks perhaps a little bit more esthetic with some anterior with some individual posterior teeth missing. So how would we accomplish that. Well, here is that broad palatal strap. And um, just a framework with what we call in the posterior a tube tooth. Okay. So here's like a little socket available for the tooth to sit over. And you're looking at an occlusal view of basically what in cross-section looks like, um, a nail head. Here is what is called a steals facing. And this is a backing of metal. And the front part has all kinds of mechanical retention that the tooth is going to bond to in the facial aspect of it. So let's see. Oh, there's our nail. And this is the mechanical slot and some cross hatches across the. The facial aspect of the facing and to which we can either bond a denture tooth, a prefabricated denture tooth whose lingual has been cut away, or some composite over it with some opaque or on the metal. Here are teeth already attached to the framework. This is part of a steel spacing and this is a tube tooth. So here we have an anterior tooth. And this is an incisal view of it. And there's the posterior tooth that is connected to the framework. Okay. So either one of them, um, is was a very esthetic application of single teeth here has a very minimal flange. Um, just because there was a minimal amount of bone that was lost and here there was no flange whatsoever, because this looks like it was just coming right from the tissue so that we don't have any, um, denture base whatsoever. So how is the how is the steels facing done again in an analog fashion? And there is a digital kind of component to this, which we'll see at the end of the course. But what we do is we select the denture tooth most appropriate for the application. We create a plaster matrix that will support the denture tooth during framework fabrication. Notice the slot in the back of the denture tooth that will fit. Against the slot of the framework and when the framework is waxed up, meaning this is what the framework will ultimately become in metal. Um, there is a piece of wax that mimics this side of the tooth so that. It will appear in the framework. Um, when the framework is returned, we take the denture tooth and slide it right down the slot and bond it into place. So what this tells us is that before we send our final cast to the lab to fabricate our framework, we're actually going to have to pick the tooth with the patient. And, and and we're going to either send the tooth, the actual physical tooth, or we're going to tell the lab which tooth we want so that the lab will be able to create that whole scenario in the laboratory and then return it back to us framework and tooth. Okay. So we need to already have a tooth selection in place at final impressions. Okay. We can't forget that. So that's really important. To set on the articulator. Of course we need a bite because we're going to need to know where to actually put the tooth. Matrix is made of plaster tooth and matrix is sent to lab. The lab trims the tooth and places the retentive slot. And then the wax up of the lingual is done with the matrix. And this is just a diagram of what is actually taking place at the tooth is set on the cast. Here's the matrix that's being fabricated. The slot is cut on the on the facing. Then everything is fabricated on the cast itself. The matrix is placed and the wax up is added to the tooth. And then the casting is made on the final cast. The plaster matrix is used to position the tooth after the casting is retrieved and bonded to the final framework. This is the clinical piece okay. This is what you are responsible for selecting the tooth and the shade. This is all the laboratory work that needs to get done behind the scenes. But you kind of need to know what the laboratory has to go through, which means your responsibility is selecting the tooth. That's it. Because you can't say please return steel spacing if you haven't provided them with the tooth information. Okay, so the framework is returned to us. This is the polished side of the facing and the framework itself. And here is the retentive side of the of the facing and the tissue side of the framework. Here is the tooth Tryon. So or the I should say here's the framework. Tryon first with the metal backing and the slot projection. So first we make sure the framework fits. And then we slide on the the tooth to make sure that everything is, uh, esthetically pleasing. And then it's cemented into place or bonded into place is far as the tube tooth goes. Um, the nail head is positioned in between, um, our two guide planes or minor connectors, and then we take our, um, our denture tooth hollow, grind the center of the tooth and slide it over. The guide planes are minor connectors, and that's bonded into place. So that's how the posterior tooth is done. We hollow out this area on either side so that it does cover up the metal, and the metal is not shown. Um, the metal is invisible so that it becomes a more esthetic restoration. And here. Here is some casting with a whole bunch of things going on. But here's a nail head tube, tooth tube tooth. And then we have a tube tooth here and a tube tooth here and a facing here. So we have a number of different applications on a single framework. Here. We have a tube tooth here and a tube tooth here, and an actually RPI class coming out of the same space. Here's a tube tooth. And a facing. So remember when we did our abutment selection? That was last year right. And I said leave a space for tooth number ten. Because when we write a prescription. Even though tooth modifications will not go on, our worksheet will not go on our prescription because these tooth modifications will already be done when we send our case to the lab. But what will need to be included in your prescription is tooth number ten. And. We need to add steel spacings under tooth modification. So the lab knows that number ten will be included in the framework. Okay. Because if we don't then the lab might think that you're you might be planning on putting an implant here or a three unit bridge. Right. So you need to tell the lab that this is going to be part of your framework. And you tell the lab by including number ten steel spacings. Any questions? Okay. Let's take a break and come back with all of these items. And then we will draw. Up. It is now. You'll come back a little bit before nine because it's about a 8:45 right now.