What Are The Common Repairs For Complete Dentures Or RPDs?
The types of materials most often used In repairs are Self-Cured Polymethylmethacrylate ( PMMA) and Triad Light Cured Composite material. These are used in the following way. First, hold the pieces of the fractured appliance together to evaluate their “fit”. If the segments don’t relate very accurately, we have a problem at this stage. Procedures in the next process:
• Final impression – elastomeric impression materials
• The final impression has to be placed in the mouth in its terminal position, and a full-arch irreversible impression in a rim lock or perforated stock tray has to be made. This impression relates RPD to the remaining teeth.
• Impression has to be poured with dental stone as soon as possible to create the working cast
What To Do When The Plaster Sets?
After the plaster sets, we have an index to relate the segments to the repair procedure itself. The denture is then lifted off the index and the edges of the broken segments are beveled toward the outer surface. This will provide fresh acrylic to allow a better repair as well as more surface area for the repaired acrylic to bond to.
We also have a large surface area for the new repair acrylic to form a bond with. The repair acrylic is checked out from the desk. Place some liquid and powder in dappen dishes and use a paintbrush to place the acrylic in the defect. Note the pre-moistening of the repair area with a monomer before placing the repair acrylic.
Triad Light Cure Alternative
As an alternative, the repair may be performed with Triad light cure material. If this technique is used, the fracture line must be given a thin coating of VLC bonding material. A small segment of pink Triad light-cured material is then placed along the fracture line and molded to fill the defect and blend with the surrounding acrylic. The plastic packet of the material is opened and a small piece of the material is cut from the sheet. The material is then shaped into a small rope and pressed into the defect at the fracture line. The material may be worked like clay at this point and blending with the surrounding material may be accomplished with a spatula and some repair acrylic liquid. The material has to be blended into the defect and the margins have to be smoothed with the spatula moistened with self-cure liquid as shown here.
Once the Triad material has been blended, it is coated with an air barrier coating before curing in the light curing unit. The reason for the coating is that the surface of the Triad is inhibited from fully curing if it is in the presence of air. The thickness of the air inhibited layer is very thin and this is the reason we don’t commonly use the ABC when making trays and base plates.
For the repair of a denture, however, we want the surface to be fully cured and use the air barrier coating. The denture is then placed in the curing unit and exposed to intense visible light for 10 minutes. The material used for the repair of the denture requires a longer curing time than the material used for trays and record bases.
The presence of air barrier coating on the surface ensures a complete cure of the outer surface of the material which provides a better finish to the cured denture. The completed repair is removed from the index and the area is smoothed with an acrylic bur. If the repair is done with self-cure acrylic rather than Triad, this procedure -will proceed in the same manner. After the repaired area is shaped and smoothed with a bur, the denture is polished with pumice and Bendick. The completed repair will blend and if it is done well it will be difficult to detect it.
Again, a broken flange was demonstrated here, but a fracture of a lower denture in half or any fracture of the base of a denture is handled in the same manner. In some cases, the matrix has been fabricated from medium-bodied PVS. The material can be removed from the denture easily. This will be the backing material when we perform a repair. The fracture line on the denture is “cleared out” and self-curing repair acrylic may be used to repair the defect.
Two types of self-cure acrylic and one “hybrid” repair combination can be used. The typical tooth repair involves an anterior tooth. By a chance the tooth will come out intact – in that case, it is just a matter of replacing the tooth with self-cure acrylic. If the tooth is fractured, which is the case here, we need to select another tooth of the same size and shade for repair. In the presented case (a broken tooth), the remains of the fractured tooth are removed with an acrylic bur.
Some care has to be taken to preserve the FGM area of the acrylic if possible. We have now created a recess into which the replacement tooth may be secured with self-cure acrylic. The replacement tooth has to be reshaped as well. It is common to shorten the cervical area of the replacement tooth. Additionally, the lingual surface needs to be reshaped and we can see that a groove has been placed on the lingual surface of the tooth. The groove gives more surface area for the repair acrylic to bond to help increase the retention of the replacement tooth in the denture repair. Reshaping the tooth is a trial-and-error procedure.
Fitting The Replacement Tooth
Here we can see that enough structure has been removed to allow the replacement tooth to “fit” into the recess provided. The tooth has not been secured with acrylic at this time; it is just set in the recess to check for fit. For the repair itself, self-cure acrylics are used. It is easier to use them by placing liquid and powder in separate dappen dishes and using a fine brush. Dip in liquid, pick up a small segment of powder, and place it around the tooth to be repaired. The brush is cleaned in between each increment of acrylic by dipping it in liquid and cleaning it on a paper towel as shown here. It may be helpful to “tack” the tooth in place with small amounts of sticky wax at the incisal edges where the circles are.
Once the acrylic has cured which takes about 5 minutes, the repair area is smoothed with a bur, and the area is polished with pumice and a wet rag wheel. Once smoothed with pumice the area is brought to a high shine using Bendick and the repair is completed.