Autopolymerizing Resin: Sprinkle Method

This method involves applying the resin to segments of the arch, waiting for initial set, and then forming other segments. Because of the need for extended use of uncombined monomer liquid, this technique is most safely performed under a hood or in a well-ventilated area.

The master cast, which has been blocked out, soaked, and coated with separating medium, is held in one hand and tilted so that the first segments to be formed are parallel to the floor. These areas are moistened by monomer liquid dispensed by an eyedropper. Polymer powder is then sifted onto the moistened areas until the liquid is slightly oversaturated (i.e., until some of the powder remains dry). More liquid is added, followed by more powder, until the material reaches a uniform thickness of about 2 mm. The last layer added should be powder to minimize the likelihood of unwanted movement of material. The cast is held in position until initial set is achieved. Then the cast is rotated to bring another segment parallel to the floor, and the resin is added until the desired thickness is achieved. Again, initial set is allowed to occur.

Autopolymerizing Resin: Finger-Adapted Dough Method

An alternative that involves less exposure to monomer begins by mixing approximately 2 tablespoons of the polymer with monomer in the proportion recommended by the manufacturer. When the mix has first lost its stickiness and has achieved a dough-like consistency, it should be rolled into a 2-3 mm thick sheet for application to the master cast. Another approach for making the mandibular record base with this material is to form the dough-like polymer into a 1/2-inch roll, place it over the ridge crest, and adapt it to the bearing area. With either method, the material must be gently but continuously adapted and readapted to the cast until the resin no longer springs away or rebounds from the cast.

Curing the Autopolymerizing Resin

With either the sprinkle-on or dough method, when the resin has achieved initial set the cast should be immersed in warm water in a pressure pot that is then pressurized to at least 20 psi for 20 minutes. After the resin is cured, the record base can be removed from the cast by placing a lab knife at the distal buccal area between the resin and the cast, using a gentle rocking, twisting motion. For both arches, begin along the posterior borders and move toward the incisor area.