Removable Partial Dentures P3
2014
So, this is your fulcrum line if it’s occlusal word forces. If it’s sticky forces trying to remove the partial and the retentive fulcrum line, it goes from the tip of the clasp to the tip of the clasp. So, that would be the removal fulcrum line.
Class II upper, same kind of a thing. You’ve got a unilateral distal extension. We basically, up here, got our primary retainer, our primary retainer, indirect retainer. Third point of reference. Here, again, they happen to put a T-bar clasp on this. What I would do a lot of times, if I could take a high speed hand piece or carburetor and disk, if I had a reasonable retentive contour at this distal labial aspect, I’d try to recontour this and cut this part off. Again, the curvature of this infrabulge and aspect, if I can get that to come down a little bit distal to the point of greatest convexity, I hide the whole thing better.
Now, with a lot of these patients, when you’re assessing the patient and you’re thinking about what you might be doing for clasp design on any of these patients, male and female, when they’re in and you take your preliminary impressions, one of the things to do with the patient is just get them so they moisten their lips. Their lips are nice and relaxed, you ask them to smile. Then, you ask them to put a really fake smile on that’s so hard it’s going to break their face, and see how high they can really fake smile.
You may get some people that even on the fake smile, they’re lip doesn’t get up far enough so that’s an issue, but that’s useful information. That’s useful information because if a person has a really high smile line, then you want to do anything you can to try to hide or diminish how obvious the clasp is. To that end, it’s going to be better if you survey these things and be looking real hard for retention at the distal labial aspect of the tooth. Hope that you do not sea frenulum attachment coming in there or a big soft tissue undercut.
Soft tissue undercuts bother me more than frenulum attachments. If aesthetics is a big deal, the patient can’t afford a precision attachment of some sort and I’ve got a frenulum in there, what do you supposed I want to do? I’m going to call my friendly neighborhood periodontist or if you do it yourself, I’m going to do a frenectomy. I’m just going to cut it away so I can put my clasp where it will be aesthetically the most pleasing, and I’ll just lose the frenulum at that point. If there’s a huge soft tissue undercut, that’s a little more difficult to deal with, but if it’s a frenulum that’s in the way, you can consider doing a frenectomy to maximize the aesthetics of your clasp.
Okay, with class II we’ve got a modification space, a front or a back modification space. So, here’s your clue: Class II unilateral distal extension, and there’s another spot that’s edential. So, here, we’re bounded by teeth so we have a distal abutment here. So, this would be a class IIP. Here is basically the framework of that, which basically shows you the posterior modification space. There’s the posterior modification space when we’re getting ready to take a bite out of it. Same kind of a thing in the mouth. Okay, here’s our class II, posterior modification space with the molar. Primary occlusal unit. Our primary occlusal retentive unit.
Another one here, primary retainer. That’s the word I’m grasping for, retainer, which includes an occlusal clasp, a retentive arm, and a reciprocal component. Either that’s going to be a lingual reciprocal arm, or it’s going to be a lingual plate that goes across the lingual of the tooth. So, we have occlusal rest, clasp component, and reciprocation component. Okay?
So, you can also have a class II. Here’s your distal extension free end, and then we’ve got both and anterior and posterior modification space on this. So, again, it’s still a class II. It happens to have two modification spaces. So, here’s that case in the mouth, combination case. You’ve got a, upper denture. You’ve got your lower partial. You’ve got your free end side with the clasp. We’ve got some modification spaces, and then, over on the other side.
Here’s the same thing in a maxillary case. Again, here, we’ve tried to make use. These were done several years ago when we took these pictures, and, over time, what we’ve tried to do with these eyebars is I tend to like a modified T-bar rather than an eyebar. The reason I like a modified T-bar rather than an eyebar is it just has a bigger footprint. It touches more tooth than this, and, again, if I can try to hide this around the back corner of the tooth, I don’t think I’d pay an aesthetic price for that.
One of our former faculty loved doing these. He would try to make this like jewelry. So, they were really fine, barely showed up at all. What do you suppose the downside of that was? They didn’t necessarily break. They just came out of retention real quick so you didn’t have a big enough footprint, and this arm that came down just wasn’t stiff enough that they were back all the time getting it adjust which, over time, led to what one individual said as they’d break.
So, if I’ve got a slightly more robust arm here and it doesn’t have to be a truck bumper on a Kenworth semi going down the road. It doesn’t have to be big, but I find that the little foot going towards the distal just gives me more square millimeters of contact with the tooth than that little area of the eyebar well, but, again, I try not to have this thing come down mid-labial on the tooth. I want it to come down on the distal labial aspect because it’s going to give me a more aesthetic partial, and depending on the patient’s smile line, they just don’t show up that much. It works out really well.
Class III. This pertains to one of the questions asked earlier. If I’ve got a class III, hypothetically I shouldn’t have to deal very much with the resorption of the edentulous ridges. So, if I’ve got an area in here or an area in here, when you get to the mouth, both of these area where they’re edentulous are bounded by teeth. So, when this person bites down really hard on their partial, they’re not squashing their gums because the partial is too supported all the way around.
So, if this was delivered last year and you wind up getting the patient 11 or 12 months after this was delivered and they’re telling you it doesn’t fit, again, what you can go on is what’s written in form 6. Form 6 says everything fit just peachy at the time it was delivered, and the occlusion was good. It doesn’t fit so good now. My first supposition is the patient either hasn’t been compliant wearing it or it got dropped. It got dropped. In either case, what’s going to happen is if the framework gets sprung, you can try to fiddle and fix it, but it’s not going to work well. If the partial is not being worn as was asked before, this distal molar and this distal molar, it’s very likely that they may in fact be pounded a little more mesially.
So, that distance from the mesial marginal ridge of this tooth to the distal proximal of this tooth will have decrease a little bit, and if you try to decrease the partial a little bit, it will seem really, really, tight because what’s happening is your partial denture’s not acting like an orthodontic appliance. You’re trying to see if you can get those distal teeth pushed upright again. So, depending on how long the patient was noncompliant about wearing it, you may or may not be able to get that much movement. You may or may not.
Now, here’s another one. Now, many times people will ask. If I’ve got a class III partial that’s completely tooth-supported, it’s very common that I will tend to use just a metal base with a bead retention because, again, if I’ve got a completely tooth-supported partial, I don’t plan on having to realign the underside of that partial because I don’t expect the gums are going to change much because I’m not putting so much pressure on them. I’m not putting any pressure. So, what I’m doing basically is a completely tooth-supported partial, pretty common that in the edentulous areas, I’m just going to put a case metal base with bead retention.
Occasionally, we’ve done this if I’ve got a tooth in this area. So, here’s a partial that’s completely tooth-supported, but were laying right over the tooth of this tooth. You may or may not be able to see very well. Sometimes what happened with these teeth is the tooth is basically cut off at the gum line, and occasionally, these will have a post-encoating put on them.
Now, can anybody imagine a reason why I might have my partial denture just go over the top of that tooth? Any thoughts? Sometimes if you take study models and mount these cases, the tooth in this area sits way up above the point of occlusion. It’s almost in contact with the upper gums, and when you look at it, it’s really obvious from the front that this tooth in the back because it was unopposed for some period of time, extruded.
So, if you’re going to leave that tooth at the height it showed up, your plane of occlusion on that side of the patient would be going way the heck up in the air where you’ve got no room to work on the upper arch. So, one of the things you want to do with study models is evaluate the orientation of your plane of occlusion. In other areas, where do you suppose you’ll learn how to evaluate the orientation of the plane of occlusion? Where do you learn that? With your denture patients. Yeah?
So, what’s a reasonable plane of occlusion? Even with the anterior to the center of the retromolar pad that you do with the denture. So, what happens to students all the time when they get these bigger cases is if there’s teeth there, no matter how screwed up or crooked the teeth are with the anatomic landmarks, somehow you people thing the teeth came off Mt. Sinai with Moses or something. Oh my god, they can’t be touched. How can we possibly work with it Dr. Shotwell?
Well, where are your anatomic landmarks? So, maybe on a tooth like this, in some cases, maybe it was already endodontically treated, and I’m not even thinking about putting a crown on it. I’m going hose that puppy right off at the gum line, and many times, how many of you have had it? You’ll get a tooth that’s the terminal tooth in the lower arch, the very last tooth in the lower arch? What do you often see concerning the gums at the distal marginal ridge of the last tooth in the lower arch? Gums are right up even with the marginal ridge tooth. Anybody had one of those? They’re fun to do crowns on aren’t they?
It’s really easy to get that nice axial wall on the distal. You people are freaking out when I say, “Give me the anesthetic” “But they’re really profoundly numb Dr. Shotwell. I gave them an inferior alveolar.” I know they are. Now, give me the anesthetic. Then, I go ahead, and I infiltrate the daylights out of this tissue right here until it turns as white as my lab coat because what am I about to do? Rotary gingitize. Okay, we’re going to vaporize it because I’ve got to get a hold of that tooth.