Removable Partial Dentures P2
2014
So, when you get gray hair and you say the same thing, they just don’t fight back as much or push back as much, but sometimes, also, it’s like the DNA on the dress. You sort of deny, deny up until there’s any controversial proof to the contrary. So, if you ask the person, “Where you wearing this?” “Yeah, yeah. Of course.” We don’t have the DNA on the dress, so to speak, to make the people change their story, but that’s another matter.
So, if we look at a class I partial here, basically, what’s a fairly common circumstance of a class I partial. You’ve got a bilateral distal extension. You’ve got primary retainers. In this case bicuspids. This happens to be a lingual bond on a lingual plate so we have an indirect retainer here. Again, if we imagine our primary fulcrum line here, we imagine sticky foods, a Milk Dud or a Juju beans or a gummy bear sticking here trying to lift this away from the tissue, the fulcrum line’s going to be through the clasp tips, and by the fact of this touching the indirect retainer or if I have lingual plate and the lingual plate touches the lingual part of the anterior teeth, that’s going to resist the back end of this thing tipping up in the air. More important than that because if anybody eats gummy bears, they’re coming out of their map in their lap anyway. They don’t stay in that tight.
The biggest reason and the biggest advantage of having indirect retainers is having an indexing position for the partial to determine whether it needs a realign. Then, if you say it doesn’t need a realign, how are we going to do the realign on the partial? Unlike a complete denture, for a partial denture what you are not going to do is you’re not going to load up the underside of these bases with a little bit of PVS, seat it in the mouth, and just tell the patient to bite together. You’re not going to do that. How come?
Can you see that overtime if the partial denture base saddled down a little bit because it lost tissue support, it’s very possible that the opposing teeth, if they were natural teeth extruded a little bit. So, if you just let them bite down, they’ll just tilt it to the same orientation it had. So, if you go ahead and put your PVS in the underside of the bases, seat the partial denture framework in and carefully hold firmly the partial denture framework so that the primary occlusal rests are down and the indirect retainer’s down. If it’s a lingual plate, you hold it so that you’re sure that that lingual plate fits down and in the teeth.
So, you’re holding the framework in its proper orientation to the teeth which is essentially just suspending the free end of partial and space over the top of the gums, and your impression material is making up the difference, rethreading the tire. People get that okay?
You send it off to the lab. The lab realigns it. So, now it’s come back, it’s got a new plastic underneath it. You fit it in the patient’s mouth. You ask him to bite down. What do you expect to see concerning the occlusion? It’s too high in the back. So, then you just adjust the occlusion on the partial as necessary to get it so that now the partial doesn’t rock front to back.
The bite’s even, but we may have adjusted the occlusion on the partial a little bit because if, in fact, the distal aspect of the partial sank down because of lost of support where the tissue changed, it’s reasonable to assume that the occlusion of the opposing arch followed it down which is why you just don’t have the patient “bite together” when you’re realigning a partial. You orient the framework correctly to the teeth, and that’s where the indirect retainers come in as a really good third point of reference for situating the framework on the teeth and knowing it’s well- seated. It’s also a great device for telling whether the partial denture is rocking. Has it lost base support? You just wait and see does it teeter-totter?
So, here’s an upper case. Now, you don’t see that much tissue to change overtime with maxillary partials. They’ve got a lot more real estate to cover. There’s a lot more square millimeters of gums to support them. This whole area across the palate is pretty good support so I don’t see the need to realign maxillary partials anywhere near anywhere the rate at which we need to realign mandibular partials because we’ve got a lot more tissue support for maxillary parts.
Here’s one. Basically, you’ve got indirect retainer. You’ve got your lingual bar, and you’ve got your clasps. So, you check things out and see do things rock? Here’s a lower one. We’ve got canine abutments. On this particular case, can you see straight down, looking on the canines, that we’ve done crowns on them both and we’ve created raised singular on the two crowns? Again, on the lingual of the cuspid as it normally exists is just that slope that goes all the way to the ground. There’s not a good vertical resting spot.
So, if the tooth, otherwise, does not need a crown, you can build that lingual aspect up with composite to create a ledge on the lingual of it and composite. You can also go to the thickest portion of the canine, the very thickest portion down on the singulum. Take a parallel-sided, flat-ended [19:10] and cut a small ledge, a fairly narrow ledge, or you can build it up with composite. Any of the three.
My main goal isn’t to leave immediately to doing crowns on teeth if they don’t otherwise need a crown other than for creating a resting spot. You can do that other ways.
Sometimes when canines are rotated, we’ll put a small little notch on the incisal edge of the canine so that this framework fits on that little notch. Canines are rotated a bit. That does not wind up being aesthetically unpleasing. Now, many times we would not use incisal hooks if we thought this was going to show very much. Rather than use this, my own prejudice would be if I could to try to use a little bit of a ledge down under the singulum at the lingual.
When we look at canine abutments on the maxilla, as much as I possibly can, what I try to do in the maxillary arch is avoid this if I can because one of the biggest complaints patients are going to have about removal partial dentures in general are actually two things. One, they come in and out. Can you give me anything that’s fixed that doesn’t come in and out? Well, depending on the number and distribution of teeth, you may not have that choice. So, one big complaint is they come in and out.
The second biggest complaint is they’re ugly. “I don’t like that big clasp showing on my tooth,” which is why anytime you get a maxillary partial denture n which you’re going to have a canine as an abutment, try to survey it in such a way if this is the canine and this is the front of the mouth here, try to work things in such a way that you see if you can come down with and infrabulge clasp arching towards the distal. So, this is the greatest convexity of the tooth.
If you look at this from the inside of the ledge, cuspid teeth or canine teeth, when you look at them from the incisal have two faces. There’s a distal face and a mesial face, and it sort of comes around like this. If this was the front of the mouth, anything you can get from here back tends to hide so the cheek is hiding it a little bit. If you can create an infrabulge clasp with a modified tier and eye at the distal labial aspect of the tooth, as close to the gums as you can get it, again, when you’re surveying these casts, the whole idea about trying to reshape the labial aspect of the tooth to get the height of contour as low as you can toward the gums.
I’d like my 10000th of an inch undercut to happen ideally about 0.5 millimeters from the gums because can you see, the closer you get your clasp to the gums, two things happen. One is it’s better mechanically because you’re grabbing closer to where the tooth comes out of the bone.
Secondarily, it’s just nicer looking aesthetically because on an upper case if the clasp was way up towards the gum, depending on where the patient smiles, their lip doesn’t come up above the clasp. So, you don’t see it, and if you’re hiding it around the distal labial of the tooth, you don’t see it.
So, over the years, I just see lots and lots of partials on maxillary cases where there is a canine involved that is far as I’m concerned are just butt ugly because somebody didn’t take the time to take a study model and survey the darn thing and see where is the height of contour. Can I come up with a survey that will give me a height of contour that tries to be at the distal labial? Then, I try to get a good enough impression so that I hope I don’t have a lot of undercut of soft tissues to contend with deeper on the vestibule where I want to come down on the tooth because if I’ve got real severe undercut up in the soft tissue in that area, then it’s difficult to do an infrabulge clasp.
On maxillary partials, wherever there’s cuspid involved, I really like to do an infrabulge claps if I can at all, and that’s what’s drawn here. The thing I would change on the drawing is that I would not take it to the mid-labial. I would take it to the distal labial, sneaking it in around this back corner. Now, if I do that, one of the other principles I’ve got to do is I’ve to grab around that tooth more than 180 degrees so the tooth doesn’t move overtime away from the partial denture framework.
So, that means I need to get some aspect of my framework as far up as that mesiolingual, as far up there as I possibly can. So, if my clasping is at the distal labial, I need to get my indirect retention or my occlusal retention or something as far around the corner, around the mesiolingual as I can so that I get 180 degrees of encirclement of the tooth so it doesn’t move overtime.
So, here’s some other cases where we’ll do this. This is starting to get to the right idea, but this is sort of if we carry it over to the mesiolingual corner and then went back. It’s the right idea, but it’s like screwed that one up a little bit because if we were doing this anyway, why didn’t we just come down, arc up a little further, and have the anterior-most aspect of that T-bar be just about mid-labial on the cuspid or a little bit distal than the mid-labial. So, my clasp engaging was right here because this, when the patient smiles, just jumps out at you. It’s sort of like this chrome hubcap looking at you when they drive by. Pretty, who did that for you? Dr. Shotwell. If you have a modification space, same thing here. You’ve got your class I because it’s a bilateral distal extension happens to have an interior modification space.
Class II is a unilateral free end, upper or lower. So, what do we got here? Basically, you’ve got your primary occlusal rest, your indirect retainer. Your fulcrum wire runs through the retainer if we’re talking about the fulcrum line that is concerned with tissueward movement. If you bite down on food in this area and you try to push this down, your fulcrum line runs across these occlusal rest. Your retentive fulcrum line if sticky foods are trying to lift the partial away from the tissue is going to go to the retentive tips of this clasp and this clasp.