Partial Dentures P2
2014
So the whole framework will go down levelled and everything engages at the same time. If there’s a curve on your path of insertion, or the rotational path, the back end seats first and then the front end rocks in. If people see if you are going to do your brock after this, one of the things you need to think through out with your brock out is on the distal side of this front tooth you can see that this is going to go off and on so if you have a pair of dividers then you put one on to the [inaudible] here and you put the other on to the [inaudible] so it just barely touched the [inaudible] the distal marginal ridge of that tooth that the arch that divided out this [inaudible] you have to brock that out. Because if your framework doesn’t fit any tighter to the distal corner of this tooth down to the cervical can you [inaudible] you try to rock it into place it wouldn’t seat at the time. That part of the proximal plate goes right here. If it wasn’t blocked out curves that line, if it fit tighter to the distal length too it wouldn’t rock into place when you seat it. So those are the things you want to look at when you want to brock it out for rotation [inaudible]. Okay, in the linear placement again all rest seats seat simultaneously. So if it’s not a curvilinear here, if it’s not a rotational path it’s just a straight up and down path of insertion for the most part, all the occlusional [inaudible] simultaneously. And you can see in this area we have brock [inaudible] where that undercut exists on the mesial of that tooth or when the undercut exists on the distal of that tooth, they [inaudible] blocked out parallel with the path of insertion. So when everything [inaudible] it just all slides down and what’s holding this partial denture framework on that tooth is an occlusal rest [inaudible]. So if you said okay in the same situation if there is a little bit of an undercut on the mesial proximal of that tooth but if I go and do a curvilinear path of insertion so that my brock out on the mesial of that tooth is entirely [inaudible] and I planned completely on having my proximal plate fit that more intimately. There’s still brock out here to allow that arching type motion to come down and clear the distal of that tooth. So if there’s not as much brock out here, there is no buccal clasp on ,there is no lingual reciprocal one. But when the partial denture is fully seated, this distal part can’t come up in the air because this proximal plate is wedged or captured in that undercut on mesial. So it’s an intentional use of that undercut without blocking it out. That’s the whole idea of rotational kind of partial. What types do you got? You got front to back, you got back to front, and in some situations you can do them sideways. So if I do basically front to back, that is very similar to the one that is right on the cover on your Krol manual. Again, if you look at that upper set of pictures it shows the case where you got a patient that’s got [inaudible] teeth being replaced when that partial denture goes into place front is going to seat first and then the back is going to rock in. So that’s going to be front to back. Okay?
We’ve got back to front and that’s the same one shown on the cover that you seat the back first and then you rock it to the front. So you got back to front or front to back and sometimes you can have a lateral. So that’s in teeth missing right here, so you’re missing basically your lateral incisor and cuspid. Instead of doing fixed partial denture they just thought could we fit a partial denture framework in there and then basically let this part seat down first and then arch or rock the partial denture down to get the clasp to the [inaudible] over here. So for as long as this part of the partial denture stays seated there is a couple of undercuts that have been gaged over our [inaudible] by rocking into them. So as long as this side stays fully seated, these things can’t lift up in the air because these are rocked in into a undercut. Categories. We got categories. Category one is more like the picture that we showed you at the very top of the lecture of the lower class 3 partial where the posterior rests would seat completely. The posterior rest seats would seat completely and then you rock the partial in place with those rest seats acting as a [inaudible] basically. Category 2 or dual path instead of [inaudible] rotation path… it is more similar to the picture on front cover of your book that’s the upper case. So the way that one works, if you got one of these clasps [inaudible] and you’re trying to make use of the undercuts on the mesials of the cuspids, or the mesials of the first bicuspids, you seta the partial denture in anterior angulation so that the end of the plane sits down first and then you rock it in. So the rest seats themselves don’t hit right away .You don’t sink the rest seats and then wrap it around the rest seats. In the back to front the rest seats are fully seated and then you rock it into place with the rest seats [inaudible]. That was that molar class 3. The upper class 4 the rest seats are not fully seated when you angle them from that front direction. You get the edge of the [inaudible] all seated and then as you brock it to place during the rocking to place the front rest seat sits and then just a little later the posterior rest seat sits.
But in the type 2 or the category 2, these rest seats are totally seated on the rotational part. You see [inaudible] dual path of insertion. So it would be seated at an angle and the rocked in. Here’s a category like one we talked about. It’s basically these rest seats sit completely. This would be the class 3 arch [inaudible] on the other side of the arch. SO this rest seat sits completely, you rock it down in place so when this is seated this wedges into the undercut. Okay, we look at basically category 2. Sometimes in these situations if you were to imagine this to have anterior teeth set out in the front, and that gain is the picture on the front to your manual. What would happen in these situations is as it was being seated in the front part seat first the end of the plane would sort of [inaudible] here but the rest seats themselves would not fully be seated. So we angle that on this forward angulation this way. Seat the flange in, start rocking it down and as it’s rocking down in place later on then the front rest seats come to rest and then last of all the back rest seats come to rest. So it’s first the flanges going in, then we start arching it, and then the rest seats of the front are seated a little bit later and the back rest seats seat last of all. But in the category 2 which is front to back or back to front, we don’t completely sink the rest seats and they are not [inaudible]. What we want to look at when we’re doing cast analysis. It’s basically sort of like any partial that we would be doing. You got to look at your plane of occlusion. And when you’re looking at the plane of occlusion, we sort of talked about that stuff, but as you got to set a cast…what does that really mean? If you are assessing the plane of occlusion can you see that if really goes up and down a lot that’s not a good thing? Or some teeth have gone missing. Let’s say posterior molar teeth are extremely up in the air and some [inaudible] upper teeth are going down. So your plane of occlusion [inaudible].
That’s’ not such a good thing. But if your plane of occlusion has posterior molars extremely tilted along way. So it seems like when you sort of look at your lower plane of occlusion it seems fairly reasonable at the front but as you get toward the back of the mouth it like really curves up in the air a lot so your overall plane of occlusion [inaudible] ski jump going up there. Not such a good thing. Maxillary plane of occlusion. Some posterior teeth on the [inaudible] have extremely [inaudible]. So your maxillary plane of occlusion goes level across here and then dives way downhill. Not such a good thing. So look at your plane of occlusion. How long is the edentulous span? Again many times what people look at is if the edentulous span is fairly short. One of the things you think about is [inaudible] fixed partial. There are some situations in which edentulous span gets longer. Think of the stress you’re potentially going to put on your buccal teeth. If you do a fixed partial denture there’s a lot. So those may fail over time. You might not just trash the teeth. Can people think of other possible problems with the really long span bridges that has nothing to do with losing the teeth or putting too much stress on them? How many people have delivered a crown and not that much later the porcelain fractured off? Anybody got one of them? [inaudible] The patient’s back and one of their complaints is a bunch of the ceramics fractured off my bridge that you’ve just done last year. Well, that kind of stuff happens as you build longer span bridges. How come? Cause the substructure may flex a little bit. And if the substructure flexes a little bit over a long span and the overriding ceramic doesn’t then it’s going to develop stress fractures and fall off. So the length of span is sort of an issue. As spans get fairly long they are almost easier to deal with an rotational path. Why? Cause spans get pretty long. If I were to imagine a molar and let’s say I had a short span not that I would do this with a rotational path. But I got a short span to bicuspid and I’m planning on making a rotational path and [inaudible] this first and then arching the partial denture down place. Let’s say I got a similar case. Molar’s the same way. Let’s say I miss first molar, I’m missing a bicuspid. [inaudible] The longer the span gets this way, at this thing arcs forward, I’ll need less block out on the distal of this tooth with a longer span that I’d need with a shorter span. [inaudible] As the radius gets longer any section of arch down here becomes more nearly a straight line. [inaudible] a very short radius your curvature here is pretty tight. So it takes a lot of block out right here. But when arch is a lot longer, arch is not nearly so tight you don’t need to block out so much. So can people see how longer edentulous span requires less block out when you’re doing a rotational path? And very short spans [inaudible] if you’re thinking about rotational path concept. The shape of the dental arch and how much undercut are we working with. So again what we’re looking. The plane of occlusion affects the depth of the undercut. So if we look here. Again, these are all in your books. Where do we locate the undercut on these?