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Denture Repairs In the lab exercise, you will do a repair of a fracture of the mandibular complete denture. This is mainly because It is easier to break the mandibular complete denture into two pieces than it is to break the maxillary complete denture into two pieces. 1. Began a repair for a complete denture by a placing the pieces of the denture together and using sticky wax to secure them in place. Then place them against the opposing denture or a cast of the opposing arch to make sure that they’re properly positioned together. If the dentures relatively new and has not been fractured due to trauma, then quite possibly a clinical remount was not done and the denture does not have bilaterally balanced occlusion. 2. Align the parts of the fractured denture and splint them into position using long shank dental burs, coat hanger wires, plastic sticks, or large paper clips. “Tack” these to the teeth with sticky wax. Avoid wooden sticks as these can absorb water and warp. 3. Block of all undesirable undercuts that are further than 10mm away from the site of the fracture. Leave enough contact around the flanges of the denture so that when a cast is poured, these peripheral edges will be in contact with the mounting plaster casts. If there is not intimate contact between the mounting plaster and the borders of the denture, the denture will rock and will not fit securely into the matrix that is provided by the mounting plaster cast. 4. When the mounting plaster cast is fully set, remove the wire or plastic braces from the teeth and clean all the sticky wax from the denture surfaces. Reassemble the pieces on the plaster repair cast to ensure that they Indeed do fit together on the mounting plaster cast before you do any alterations to the dentures. Once alterations are made, the ability to assemble the denture to its original shape is lost. The area under the fracture line must be accurately reproduced in the mounting plaster cast. If there any bubbles or voids, a new cast must be made. 5. Since the repair acrylic should be more strong than the old acrylic of the denture along the fracture line, adequate space must be provided to allow access to the repair site and to provide the strength needed for the repair to be successful. This is done by removing enough acrylic and along the fracture line and tapering it so that when the pieces are placed back on the repair cast, adequate space is provided to place the acrylic into all areas without any restriction. This is done by providing a 3mm gap to the polished side of the denture and a 2mm gap on the tissue surface of the denture. 6. In a process called “rabbeting”, the bonding surface along the repair site is prepared so that the repair acrylic will be bonded to the old denture acrylic in sufficient amounts that the denture won’t break. This is done by trimming halfway through the denture base acrylic on the polished side and extending the gap on that surface so there is about 8mm of width. 7. Before placing the denture pieces on the cast and making the repair, the tissue surface of the cast must be painted with a tin foil substitutes to prevent the acrylic from the leaching into the plaster cast and bonding the repair sites to the cast. Vasoline or Triad model release agent will not work for this purpose. A small bend-a-brush or sable brush is used to apply the repair acrylic to the repair site in a process called “brush beading”, where the tip of the brush it is dipped into monomer and then into a dappen dish of repair acrylic. The brush is used to deposit the acrylic on the repair site, where it is wetted with more monomer so that it does not dry out before it is cured. It is then placed In a pressure pot of warm water under pressure where it is allowed to cure for ten minutes. 8. After the acrylic has set for 10 minutes, remove the denture repair from the stone matrix and finish the denture with successively finer abrasives until a high shine as achieved. Check the tissue side for any irregularities, then repair or smooth them. If you have properly overbuilt the acrylic, you should have to cut back only a small amount of acrylic to achieve the desired thickness. 9. When the repair site is fully polished, in inspection of the denture shows a smooth line at the junction of the denture base acrylic and the repair acrylic. A thin red line shows that the repair acrylic has permeated the crack in the tooth. This tooth can now be replaced in a subsequent procedure. The tooth was not repaired along with denture base repair because it was necessary to be in place to provide the stability necessary for the parts of the denture to be correctly positioned. 10. Repairs to the mandibular denture are very similar to those repairs done on the maxillary denture. Because his denture is easier to break in the lab, the lower denture is it one that you will make your denture-based repair upon. Clinically you would use a repair resin that is basically the same color as a patient’s denture base. In the lab exercise, we will use Duralay resin, because we will want to be able to see exactly where the juncture between the repair and a denture base is located. 11. Again, we will use pieces of wire or paper clips, or pieces of plastic to splint the pieces of the denture together. We use sticky wax to bond these splints to the denture pieces. After the denture pieces are splinted together, turn the denture over and inspect it to see that the pieces are still in very close approximation. If they are not, the pieces will be need to be separated and reassembled so that they fit precisely together. 12. You can use polyvinylsiloxlane putty to block out a little bit of the undercuts, but you must not have blocked out any closer than 2 mm on the edge of the flange, so that this will be able to be imprinted in the repair casts vestibular area. Use bent pieces of wire, such as paperclips, with the loop end embedded in the putty to provide the mechanical retention that is necessary to hold it securely to the cast. Once the putty has hardened, use mounting plaster to pour the repair cast. 13. Once the cast has hardened, remove all the splinting material and sticky wax from the surface of the dentures. Clean off any debris from the cast, and replace the denture pieces back on the cast to see if they fit precisely into the index formed by the cast. You will need to be sure that they fit precisely into the grooves in the cast and over the ridge areas before removing any acrylic from the repair site. 14. You will then cut back the acrylic in the area of the fracture about 11/2 mm from the polished side of the dentures, and about 1 mm from the tissue side of the dentures. This will provide a space that is tapered from 3 mm wide on the polished side to 2 mm wide on the tissue side in the repair site, which will allow sufficient access for the acrylic to be placed throughout its entirety. 15. Remove enough acrylic from the polished surface side of the denture to allow a gap of 8-10 mm. This process is called “rabbeting”and provides an increased surface area that affords a stronger joint between the old and new acrylic. The top picture to the right shows the bevel from the tissue surface to the cast. The bottom picture on the right shows the extended surface area provided by the removal of acrylic from the polished surface of the denture and increase the amount of bonding surface for the acrylic. 16. ALCOTE, a tin-foil substitute is used to paint the area under the site to be repaired. Then the denture parts are placed on the cast luted in place with sticky wax. A large amount of visual and working access is provided by the rabbeting and beveling. 17. The “brush-bead” method is used to apply repair acrylic to the denture in this exercise. Two dappen dishes containing monomer and polymer are arranged close to the denture and they bend-a-brush is dipped in the liquid monomer, then in the polymer powder. This will cause a small bead to form on the wetted end of the brush. Successive beads are placed in the repair site to make the repair. 18. These pictures show the operation of applying the beads of acrylic to the repair site. The steps in the process are: (1) Wet the fragment edges with monomer. (2) Moisten brush in monomer and dip it in polymer. (3) Brush bead the wet polymer on the repair site. (4) Add additional acrylic until the entire site is slightly over-filled. 19. 20. The repair cast with the denture attached is placed in a water bath to cure. While the denture is curing, the brush is dipped in monomer and dried thoroughly on a paper towel to remove any residual acrylic to prevent ruining the brush. If this step is forgotten, the acrylic will harden and the brush will be ruined. 21. The secret of forming a good quality acrylic in the repair site is to add extra acrylic to overbuild the repair site area, which will assure that there is sufficient thickness of high quality acrylic. Moisture from the water bath can cause a rough surface to form, and this added thickness will allow sufficient acrylic to be removed from the external surface so that the surface that is left is very dense. The denture is then removed from the repair cast and the tissue side is inspected to verify that it has been repaired. 22. The denture is removed from the cast and checked to make sure that the acrylic is of good quality and covers all the desired areas. If there is still a defect present, a small amount in of acrylic is brush-beaded into the defect to slightly overfill the area, cured, and cut back as close to the original form as possible. 23. The denture is placed against the opposing denture or cast of the restored arch and inspected to ensure that the two occlude properly. If the occlusion is off, then the repair is not accurate, and the registration has been destroyed during the process of repairing the denture. Another possibility is that the patient may have given you a mismatched set in hopes of getting a new denture made for free. 24. After ensuring that the dentures fit together properly, remove the excess acrylic with a denture bur and use abrasives and polishing agents to polish the repaired area, taking care to not over-polish the area or the teeth. Also be sure to change the polishing wheel for each abrasive. 25. Clinically, the repair site on a complete denture will be almost imperceptible to the naked eye. Here is a lower complete denture that was repaired in the clinic. Can you tell where this denture has been repaired? You have to look closely to discern the repair site because the repair acrylic blends together so precisely with the original acrylic. This is how a repair should look!
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