Skip to 0 minutes and 9 secondsHello, my name's Tony Johnson, and I'm going to be taking you through the various stages that are involved in making a complete denture. And we're going to start off by talking about what the dentist does initially when the patient first goes into the surgery. And he uses something called a stock tray, which is a tray that fits the patient's mouth but not accurately. It's the best we can get, and so it might be a little bit loose in places and doesn't really confine and control the impression material which is used inside it.
Skip to 0 minutes and 46 secondsBut it gives us a working impression from which we can produce a model, a primary model, which we can then use to make a tray that's going to be a little bit more accurate. So the one I've done earlier we can now start to make the tray. So this is the material we're going to use. It's a light-curing composite blank, which is quite flexible and will stay flexible until we cure it. And we can pop it onto the model and adapt it around the model so it fits really tightly against that model and will only fit that patient. So unlike the stock tray that we used initially, this one will control and confine the impression material perfectly.
Skip to 1 minute and 37 secondsWe can then use the excess material to form a handle, which the dentist will use to hold the tray in the patient's mouth. And once we've got that into the right shape, we can then pop that into a curing bath, a light curing bath, for about three minutes. And the light will then cure the material and turn it hard. When it comes out, we have the trays nice and hard. So they're all hard, and we can then start to trim them up. So we do that with one of our little laboratory hand pieces.
Skip to 2 minutes and 25 secondsThere we go. And we can now see that we've got all this overextended part of the model is now not included in our tray. And the next impression should be much more accurate. The dentist will give us, as before with the special tray, we get an impression from the dentist of the patient's jaws, and we cast a model from that. This second model will be the model onto which the denture is made. So again, we've got two parts to this registration block. The first is the base, we're going to use a light-curing composite blank again, which we adapt exactly the same as when we made the special tray. Once that's cured, we get our base back again.
Skip to 3 minutes and 22 secondsWe can try it with the burrs again to trim off any little bits of excess, smooth it off, and we now have the base onto which we're going to put our wax block. So we've got our preformed wax block, which is now nicely soft, and we can easily bend it to shape. We're going to just melt the sticky wax. Melt the wax and pop the two together. And we want the wax to be quite prominent at the front of the block to replicate the prominence of anterior teeth. And we press the wax block down into the base, trim off the excess at the back, and then melt the wax onto the base with a hot knife like so.
Skip to 4 minutes and 47 secondsWe can use average measurements. And we know that from the lowest point of the sulcus at the front of the mouth-- that is the lips, lowest point of the lips-- is about 22 millimetres. And we can mark that position on the block and then use this little device, which is an occlusal rim inclinator, which creates the anteroposterior slope that all our teeth have. And again it creates an average slope. And we can heat the plate.
Skip to 5 minutes and 20 secondsAnd then I can use this plate to create the anteroposterior slope. So I pop it on the wax. It will heat the excess wax away down to the 22 millimetre mark in the upper and create a nice anteroposterior slope on the block. OK, so once we've made the occlusal registration blocks, they go into the surgery for the patient's third visit. And the dentist uses these to register the occlusion. That is to position the jaws correctly over each other to get the labial contour-- that is where the cheeks, lips will fall against the dentures-- into a natural position. And then he would then lock that together like this with some what we call bite registration material.
Skip to 6 minutes and 9 secondsAnd that's locked together in the mouth in that position. Once we have the registration rims, we would put the patient's models into those rims. And then we position the models and the registration blocks onto the articulator using an elastic band to get the occlusal plane level and using a little pin at the front, which you can see there, to get the relationship of the central incisors correct. And once we've done that, we would then lock the models onto the articulator using plaster of paris. OK, so once we've got the blocks mounted on the articulator, the next stage is to use the teeth that the dentist has selected and to start to create the patient's dentures and wax that into place.
Skip to 7 minutes and 13 secondsLike so. So once we've got all the teeth on, it still looks a little bit rough. The wax work needs quite a lot of work doing to it. If I just show you quickly on some of the upper teeth, we then need to make sure that that wax work mirrors as much as possible what the patient's natural tissues look like.
Skip to 7 minutes and 48 secondsAnd as it cools, we trim around the necks of the teeth and smooth the wax off. Now, this is where we can age the dentures to some extent, because as you get older, your gums recede a little bit. So somebody who's 80 years old will probably have a little bit more of that wax removed to show just the beginnings of the roots of their teeth than if we were doing it for somebody who was, say 30 or 40 who wouldn't have that level of recession. We've got the teeth set up in their right position the wax work neatly trimmed. We can see if we look up on the inside that the teeth are all meeting together nicely.
Skip to 8 minutes and 34 secondsThere are no gaps between them. And it's nice and smooth and clean, and that can now go back to the dentist for the fourth patient's visit, which is what we call the try in. So the final stage in making the dentures is to convert from the wax into acrylic resin, which is a plastic material. And we use a two-part flask. So we've got a flask which has got two halves. The first half will have white plaster of Paris in it, the same sort of stuff that you have if you break your arm. And it embeds the model part of the denture, if you like, into that one half.
Skip to 9 minutes and 14 secondsAnd we let that set, and then we put the two halves of the flask together, and we then fill the second half with another material, which is a little bit stronger, which will cover, and coat, and form a mould of the teeth and the wax part of the denture. So we'll mix some plaster of Paris. So once the plaster block has set inside the mould, we can take these locating bolts out.
Skip to 9 minutes and 57 secondsAnd we're going to put it into a bath, which will spray warm hot water, warmish hot water onto it to soften the wax inside. I'll take the flask out of the boiling machine, bring it across here, and we can now open the two halves up. Now we're going to mix the acrylic resin that we use to make our dentures. It comes in the form of a liquid called monomer and a powder called polymer. So I'm going to take it out of the mixing pot, mould it round so it's a nice uniform colour. We don't want any streaks in it, so we make sure it's nicely mixed together.
Skip to 11 minutes and 2 secondsAnd then we're going to press it into the mould and then turn the moulds over onto each other like so. Get our locating bolts and then very slowly close them down to squeeze the excess out until we get the flasks as near as possible to being closed together. That's it. And the excess material can be taken away, and we can see that it's gone from being reasonably thick to really, really tissue paper thin. So once the flask's processed in the water bath overnight, we can take it out. And we can now start to take the flasks apart.
Skip to 12 minutes and 2 secondsWe can just loosen the flasks a little bit, then tap the bases.
Skip to 12 minutes and 26 secondsSo we've now taken our blocks of plaster out.
Skip to 12 minutes and 32 secondsAnd we know that the model's in the white plaster, and the teeth and the denture is in the yellow plaster. So we can just knock away the plaster from around the model.
Skip to 12 minutes and 54 secondsSo we reveal the model again. And we can now see the excess denture material, which is called flash, which comes around the side. So the next stage is to get a plaster saw and to cut along that line where the teeth are.
Skip to 13 minutes and 24 secondsAnd so we've got the plaster block away from the outside of the denture. And then use my knife to just carefully loosen and remove the bits of plaster from the middle of the denture. And there we have our acrylic denture. So everything that was wax is now acrylic resin. So once we've what we call de-flasked the denture, we've got it out of the two-part mould and the plaster block. Take it off the model, we can see that there's this flash material on there, which we need to remove. And we then use our burr to grind off the excess material. And then we polish the surface of the acrylic resin with pumice, Tripoli to give it a nice high shine.
Skip to 14 minutes and 18 secondsAnd when we finish doing that, the dentures look something like this, so that we've got our dentures nicely trimmed. They're highly polished. We can texturise the front of the dentures where the general public, the patients are likely to see that part of the denture, so that's it looks a little bit more like gum. But at the back of the denture and on the insides where nobody sees it, we want it to be highly polished so the patient can keep it nice and clean. It feels nice and smooth to the tongue. And it's the same with the upper one, where we have a nice, smooth, highly polished palate. And we've stippled, contured, texturised the front of the denture.
Skip to 15 minutes and 8 secondsAnd you can see that all the plaster that was between the teeth has now been removed. And everything's been finished, nicely smoothed, ready to go back into the patient's mouth. So at this stage, what we had in wax for the try in like that has been exactly copied into the acrylic. So we've completely converted it from a wax try in to exactly the same thing, but now it's got an acrylic base holding the teeth tightly onto the base.
See how they're made: Dentures
In this video we visit Dr Tony Johnson, Dental Technician, in the dental laboratory to observe how dentures are made.
You will see the skills of the dental technician, the specialist equipment used, and some of the materials we have been learning about so far on the course.
The construction of dentures requires a patient to attend a number of visits to the dentist, with the dental technician making a sequence of models, trays and ‘try-ins’ before the completed dentures are fitted. The following is a brief overview of the steps required to provide a set of dentures for a patient, and the video shows you each step in the dental laboratory (with the time it is shown in the video in brackets).
- The dentist takes the primary impressions of the patient’s mouth using an impression material contained in a stock tray (a pre-made impression tray that comes in a number of sizes, and the dentist will use the size that best fits the patient’s mouth).
- The impressions are given to the dental technician, who casts plaster models from the impressions. These are called the primary models.
- The technician will make customised impression trays for the patient using the primary models that will provide much more accurate impressions. These are called special trays and allow for a much better quality impression to be taken by fitting the mouth closely, and providing an even support for the impression material (think of it as the difference between ‘off the peg’ and tailored clothes). (1:00)
- The dentist will take new impressions using the special trays and send them to the dental technician.
- The technician will cast up the new models, and these are the working models that the dentures will be constructed on.
- Before the dentures can be made, registration blocks are first constructed. These are made from wax (often with a resin-base for rigidity). The blocks are made to occupy the space in the mouth where the dentures will be and provide means of recording where the teeth will need to be placed. (2:55)
- The registration blocks are placed into the patient’s mouth and the dentist adjusts them for height (recording where the upper and lower teeth will meet), and contour so that they mimic as closely as possible the patient’s missing teeth. The blocks are returned to the technician.
- The models and registration blocks are mounted onto an articulator: a device that mimics the patient’s jaw movements. (6:12)
- Pre-made acrylic teeth are placed into the blocks, keeping everything aligned within the boundaries defined by the dentist during step 7. The upper anterior teeth are usually placed first. The lowers and posterior teeth are placed after. (6:48)
- Denture teeth are placed in such a way that there is usually always a bilateral (each side) contact between the upper and lower denture, to stop them tipping during talking and chewing. This is called balanced occlusion and is different to what is found naturally.
- The denture is waxed up, using wax to make the soft tissue areas mirror as closely as possible natural gums. (7:15)
- The dentures are returned to the dentist at this point for a try-in, where they are checked for fit, function and aesthetics. Any changes required are relatively simple to do as the denture is made from soft wax.
- The completed denture, on its plaster model, is placed into a 2-part mould called a flask. Plaster of Paris is poured over the dentures in such a way that the mould can later be separated. A separating medium called sodium alginate acts as a separating skin to allow the mould to later come apart again. (8:45)
- The wax dentures, still in the closed flasks are placed into hot water to melt the wax. The flask is then opened gently, and the remaining wax washed away with further hot water to leave a mould containing the acrylic teeth embedded with it. (9:50)
- The mould is filled with pink acrylic-resin dough, closed and compressed until it is cured. The curing takes place in hot water and takes a few hours. (10:20)
- The now acrylic dentures are retrieved from the flasks, which requires the use of saws and chisels. (11:55)
- The dentures are fitted back onto the articulator to be ground in where any increased height in the denture from the moulding process is corrected. (13:55)
- The dentures are cleaned, polished and returned to the dentist for fitting.
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