Pontic Design PDF

Pontic Design Fixed bridge = fixed partial dentures It is possible that within our career we’ll see implants take over bridges But there is still a huge population that already has bridge work and if they fail, they will most likely be replaced by bridge work as well Replacement tooth on the fixed b...

Pontic Design Fixed bridge = fixed partial dentures It is possible that within our career we’ll see implants take over bridges But there is still a huge population that already has bridge work and if they fail, they will most likely be replaced by bridge work as well Replacement tooth on the fixed bridge = pontic Hygienic pontic à is a design that is less and less used because of its lack of esthetics. Nowadays esthetics is a very important factor. Hygienic pontics (or sanitary pontics) is lifted well off the tissue, which makes it very easy to clean and maintain When a patient looks at himself in the mirror, we want the pontic to look similar to a natural tooth OVATE PONTIC (The pontic design that is most used today) à called like that because it has an oval shape. o It is the most popular because it mimics nature the best (Pontic A in diagram). o The ovate pontic has an oval underside which makes it easy to place a floss underneath and slide it from side to side of the under surface, which will keep things clean. o This is the design that most dentists today will use when they extract a tooth and temporize it, and they’d set up the temporary to sit on the gingiva into the socket a little bit which will help the gingiva take a proper shape and generate a natural tooth form of the gingiva. o It appears to be growing out of the tissue, which makes it esthetic. BULLET PONTIC à it looks like a bullet in shape, because of the way it touches the ridge in a point (pontic B in the diagram) RIDGE-LAP PONTIC o Sits on residual ridge and rests on top of it. o IT IS HARD TO CLEAN underneath it because of the concave surface underneath. o It was popular in the past because it looked the most natural back then (pontic C) MODIFIED RIDGELAP PONTIC o It tries to take the best of both worlds. o On the facial surface it tried to rest on the tissue to give a natural look, but on the lingual surface it tried to open up to allow cleansability. (Pontic D) On the picture on the left, if the pontic were to follow the contour of the natural tooth, it would give the appearance of a very long tooth, especially if some resorption occurs after extraction and the facial aspect of the pontic is made to touch the tissues. So instead of doing that, the pontic is curled in into a bullet like shape which will touch the tissues at a higher level and fool the eye by looking the same length as the adjacent crowns. Shows where the natural tooth contour would be Diagram on the left shows again bullet pontics and their use. The bullet pontic design is not the most esthetic but is very cleansable. In the drawing B some resorption occurs so the shape of the pontic was adapted a little to accommodate the ridge shape Diagram on the left: “A” shows modified ridge lap (better picture than the other one). It’s true that usually you would do an ovate pontic, but if you have a patient who has a ridge and tissues that have already healed (and you or the patient don’t want to do some minor surgery to modify the shape of the tissues for and more natural looking ovate pontic), the modified ridgelap would be the pontic design of choice. If the patient is okay with reshaping the tissue then you can do that and then place an ovate. But if they don’t, modified ridgelap design is the way to go. On the buccal surface it rests on the ridge and has a sort of concave shape. Then on the lingual side it will have a convex shape, which will make it easy to clean. That is important because if the patient accumulates a lot of food debris underneath it, it will promote tissue irritation and damage, but also cause recurrent decay on the abutment teeth. The reason why a bridge work fails is more often because of the presence of recurrent decay on the abutment teeth. Diagrams on the left: the fine line shows the contour of the original tooth. And H is the apparent height of the natural tooth. o When the tooth is extracted, some resorption will occur and the ridge will change somewhat. o If the facial surface of the pontic is made to reach the point where the ridge starts, it will make the tooth look too long. o So instead, the facial surface is curved in (like shown by the dark thick line on figure A) to fool the eye. Any close observation will obviously let the observer know that it’s a fake tooth, but the purpose of it is to fool the eye when the observer is not focusing on it for a long time. o Figure B illustrates the same concept, the dotted line shows you how long the facial of the pontic would have been if the surface had been elongated to touch the ridge facially following the curvature of the extracted natural tooth When we do our bridge, we mostly do PFM bridges. There is a metal substructure. The nice thing about that is that we can try-in the substructure, and if it doesn’t fit well, we can cut it up into pieces to check if the individual abutments seat well. If they do, then we do a step called “solder relationship” in which we solder the pieces back together in the new relationship. With all ceramic bridgework we don’t have that ability. If it doesn’t fit right you have to throw it away and do it over again. There are two sides to this: time wise it’s a loss for the dentist, but in terms of wasted material, the waste is virtually non-existent. For example if you do a zirconia framework, one “hockey puck” of zirconia material in the lab costs 1$ or 2, and a dozen or so of frameworks can be made out of it. So the lab can mill you out that bridge for almost no cost. That is also why the “revolution” is pushing things towards the all-ceramics (there is no gold or metal, it costs almost nothing). The diagram on the left shows that as the length of the bridge increases, the amount of flexure it experiences under the same force is higher (the force doesn’t change, but the span increases). o If the span is twice as long, it flexes 8 times as much. o If it’s 3 times as long, it flexes is 27 times as much. o This has relevance in how long our framework can be, and how strong the metal is. o The way we can combat the flexure problem is by increasing the height of the framework in a gingiva-occlusal direction (increasing the width in a bucco-lingual direction helps some too). o The taller the connectors are, the better the framework can combat flexure. Connectors should be as tall as we can without being too long and too close to the tissue (if too close to the tissue it becomes un-cleansable). o You need to leave room for the patient to floss under it and clean it well. o The connector is rounded underneath so that plaque and food doesn’t get trapped easily. o Sometimes the connector goes all the way up to the occlusal surface, and sometimes not: it depends on the esthetic demands versus the function of the bridge. On the left: These were old connectors that illustrate tall connectors very well. They were very tall (porcelain would be added on top) and this made the framework much less flexible. The less flexure you have, the more solid you make a frame, the less failure you’ll have later. Usually if it is too long it will be visible on the occlusal. Side Note: At BU they go crazy when crowns are involved with partials because of surveying crowned teeth, they survey them over and over and over again before they cement them. The lower molar is set up for a C-clasp it seems. The premolars have DO rests that seem like they are set up for C-claps. At BU they would never EVER do a C-claps for a distal extension. If it were set up for a combo clasp it would be okay. A C-clasp by nature, if there are forces on the distal part of the denture, it would create torque on the clasp area. You can see how the framework is scalloped on the lingual surface of the anteriors: that makes the connectors taller, which means that the 4 incisors shouldn’t flex too much. Looking at it from the buccal you can see the finish lines are kept supragingival when we could, and this was okay because the only way we could see them was by retracting the patient’s lower lip. If it’s not going to show, why not stay supragingival! The pontic design here looks like a modified ridge lap because it rests on the tissue, and on the lingual they start at the crest of the ridge and curve up This is a hygienic pontic. Very easy to clean. You can see how it’s lifted off the tissues. In this case, is there an esthetic reason this type of design shouldn’t be used? No, since the bridge is in gold, and unaesthetic anyway. Above, you can see the tall connectors, it looks pretty solid, yet there is enough room underneath for the patient to clean well. The design we’re headed for here is a modified ridge lap pontic at this point. The bottom part of it will stay metal, and will rest on the ridge so there will be polished metal on the ridge. Try-in of the same framework in the mouth. Notice we’re staying slightly supragingival because first it is a posterior area that is not likely to show, and second the premolar in front of the framework already has a gold onlay, so esthetics is not a major concern. There is no point in burying the margin and irritating the gingiva when it isn’t necessary The porcelain has been added. You can clearly see the modified ridge lap design. Bridge placed in mouth. Again, the margin is showing and that’s fine. But you need to warn the patient about the metal collar showing from the beginning so that they are prepared for that, and tell them that it would only show when they pull their cheek away. Also explain the advantages of having it like that (easier to clean, less irritating to the tissues, etc.). Tooth #8 was damaged and extracted. A modified ridge lap pontic on a bridge was made to replace it. Does it look perfect? No. Is it visible in a normal smile? No, so it’s okay. But this was done years ago. Today, we would graft the extraction area much more aggressively than it was done back then. Grafting works pretty well now. So ideally, grafting, and an ovate pontic design. The problem with the Maryland bridge is that they don’t work very well. For it to work well, you really have to prepare it to sit really well on the adjacent teeth. Initially, Maryland bridges were just bonded on the lingual surface of the adjacent teeth without preparing them at all. But the problem is that the bonding was never very strong, and so what would happen is that dentists would try to make more and more elaborate preparation to the neighboring teeth à problem with that is the more you prepare the teeth, the less advantageous the Maryland bridge is. So it has been disappearing slowly. And also, implants have become more and more predictable and become the first choice in a case like this. Nowadays, Maryland bridges are mostly used as long-term temporaries: the above case shows a 14 year old with congenitally missing laterals where the orthodontist has left space and the child is too young to get an implant since you want bone to finish growing then place an implant. You can use a Maryland bridge, then replace with implants later on. In the above pictures, the Maryland bridge has a modified ridge lap pontic design. You can also see that the framework was designed for maximum coverage on the lingual surface of the adjacent teeth, and that causes the metal to show through at the incisal edges (especially on the central incisor). That is not acceptable. So what you do when doing a Maryland bridge: when you try it in, you start cutting the metal back until you can’t see the metal showing through anymore when looking at the facial. At a minimum you want a bit of a rest seat on the cingulum or grooves so that when it is seated, it has a solid stop and doesn’t move around (very similar to guide planes on a partial). The porcelain added as a modified ridge lap. In anteriors it’s difficult to achieve perfect esthetics due to the concavity of the ridge resorption that occurs. This patient came in. His job is repairing televisions, which is a job becoming irrelevant due to technology. He is old and doesn’t have much money. The tooth failed and had to be extracted. A temp was made with a giant ovate pontic. It healed beautifully. The point here is just to see that the tissues healed really well It’s obviously not an esthetic solution but it was a good solution given the circumstances and financial issues of the patient. Ovate pontic: it really fools the eye into thinking it’s a real tooth how it’s coming out of the tissues Little tooth is a crown over an implant that the patient was really not happy with due to bad esthetics. The reason why it was placed like this was that the ridge was a little lingual to the rest of the teeth, and instead of grafting and placing the implant in the right position, the periodontist just placed it however he could with the existing ridge, making the tooth look small and lingually placed. This was done a few years ago, so the grafts were not as easy and predictable as they are today. So what was suggested was to cut a little bit of tissue facially and make a restoration that ridge-lapped and looked like a tooth. Was it easily cleansable? No, the patient had to put some extra effort in keeping it clean, but it looked much better. So the implant stayed untouched, and the original abutment was used, but the new restoration sat more labially on top of the ridge This patient had a very strong bite, and at some point his restoration and implants failed multiple times. What they did was replace the porcelain bridge with a temporary bridge, and what that did was kind of cushion the biting forces and the implants stopped failing. But obviously he destroyed his temps every 5 to 6 years too. So every few years he replaced the implants that failed and replaced the bridge made in acrylic. That worked for him for a long while. In the pictures above you can see how new implants were replaced for #8 and 9. The implant on #9 was not ideally placed, and was a little lingual. Could the periodontist have done a graft? Yes, but it would’ve been a complete waste of time, since his bite is so strong and grafted bone is much softer than regular bone so the risk of the implant failing there would be much higher. So what they did was cantilever a little bit off of the implant (labially) compared to where the implant was. A shell was made to show where the eventual temporaries sat so that the technician could wax up the cast accordingly All metal touching tissue or exposed to the surface was smoothed out, and you can see in the picture how the framework is ridge-lapped. Obviously the patient needs to make more of an effort for flossing and cleaning but it’s manageable. The frameworks were placed and the temp was relined on top of them. The temporary bridge was quite old and beat up at that point and would need to be replaced soon. All of these tricks were combined to compensate for the lingually placed implant Then he went on talking about middle-aged divorcees and patient expectations. You want your patient’s expectations to be realistic. Often when they believe that fixing their smile will make their whole life better, they will most likely be disappointed and constantly dissatisfied. So you need to tamper those expectations when they are too far-fetched. When for example doing temporary bondings on incisors, explain to the patient that it will not look perfect, because the problem with temporary materials is that we can never get the perfect shade we want, so the color is always a little off. It can still give the patient an idea of where you’re headed. Then you make the permanent veneers. Veneers allow you to change shape, change color, without removing too much tooth structure. Some studies found that veneers strengthen the remaining tooth structure. You can correct arch form with the veneers by removing more on one tooth compared to another.