Skip to 0 minutes and 4 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 fit 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 41 secondsBut it gives 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 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 23 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 with a little rotary burr in it, tungsten carbide burr. We have an extraction unit, which will suck away all the dust.
Skip to 2 minutes and 16 secondsAnd the little motor goes around, and we can - all this overextended part of the model is now not included in our tray, and the next impression should be much more accurate. 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. And 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 can get our base back again.
Skip to 3 minutes and 21 secondsWe can trim 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 going to put our wax block.
Skip to 3 minutes and 35 secondsSo 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, trim off the excess at the back.
Skip to 4 minutes and 20 secondsAnd then melt the wax onto the base with a hot knife.
Skip to 4 minutes and 31 secondsWe can use average measurements. And we know that from the lowest points of at sulcus at the front of the mouth - that is the lips, the 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, and then I can use this plate to create the anteroposterior slope.
Skip to 5 minutes and 10 secondsSo 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 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. So we've now got the posterior teeth meeting together nicely, and we want to start putting the anterior teeth on. So we've cut the base away to give us a bit more room.
Skip to 5 minutes and 46 secondsAnd we're going to warm the wax in that area like that, and position these teeth to meet the uppers and to be in a position where they're going to be stable and allow the patient to bite chunks off their food without the dentures moving about too much. 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 waxwork mirrors as much as possible what the patient's natural tissues look like.
Skip to 6 minutes and 36 secondsSo we add the wax on. Then as it cools, we trim round the necks of the teeth, and then using the little flame again, just go over and smooth the wax so it's nice and smooth, and it looks something like that when we come to send it to the clinician for the third visit. So the final stage in making a denture is to convert it from the wax into acrylic resin, which is a plastic material. 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.
Skip to 7 minutes and 25 secondsAnd then we put the two halves of the flash 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 once the plaster block is set inside the mould, we can take these low-casing bolts out, and we're going to put it into a bath, which will spray warm, hot water onto it - warmish, hot water onto it - to soften the wax inside. And we can now open the two halves up.
Skip to 8 minutes and 2 secondsWe're going to mix the acrylic resin that we use to make our dentures, and then we're going to press it into the mould until we get the flasks as near as possible to being close together. So we've got it under pressure in the brass flask, and around the plaster. And we're going to now take it and pop it into a water bath, which we're going to heat up overnight to cure the resin. So once the flask has processed in the water bath overnight, we can take it out, and we can now start to take the flasks apart, then use my knife to just carefully loosen and remove the bit of plaster from the middle of the denture.
Skip to 8 minutes and 51 secondsAnd 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's out of the two-part mould and the plaster block, take if off the model, we can see that there's this flash material on there, which we need to remove. And then we polish the surface of the acrylic resin with pumice tripoli to give it a nice high shine. We can texturize the front of the dentures where the patients are likely to see that part of the denture so that it looks a little bit more like gum.
Skip to 9 minutes and 33 secondsSo 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). (0:53)
- 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. (2:54)
- 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. (5:22)
- 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.
- 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. (6:12)
- 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. (7:06)
- 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. (7:41)
- 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.
- The now acrylic dentures are retrieved from the flasks, which requires the use of saws and chisels. (8:29)
- 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. (9:00)
- The dentures are cleaned, polished and returned to the dentist for fitting.
© University of Sheffield