Tooth movement and dimensional change of denture base materials using two investment methods.

This in vitro investigation evaluated methods of investing a maxillary denture (1) by using a silicone rubber and gypsum base covering all the artificial teeth and (2) by following the generally accepted procedure of investing in a total gypsum environment. The amount of vertical opening found in dentures processed with silicone investment was approximately the same as for those processed with the all-gypsum technique, the horizontal movement of the teeth was more lingual in the silicone investment technique. Comparing the weight of the residual impression between the denture base of acrylic resin and the master die showed no significant difference between the silicone investments and the gypsum technique. The relined denture base provided a more accurate fit than a heat-cured denture processed in both types of investment, silicone and all-gypsum. Finally, a special device was developed that permitted tooth movement in processed dentures to be measured simply and accurately.