INFLUENCE OF THICKNESS INCREASE OF INTRAORAL AUTOPOLYMERIZING HARD DENTURE BASE LINERS ON THE TEMPERATURE RISE DURING THE POLYMERIZATION PROCESS

Statement of problem. Increasing the thickness of intraoral autopolymerizing hard denture base liners may result in a temperature rise and a burning sensation for patients. Purpose. The purpose of the study was to determine whether increasing the thickness of hard autopolymerizing reline resin increases the temperature of the basal seat area of a denture during the polymerization process. Material and methods. Four polyethyl methacrylate and 1 polymethyl methacrylate autopolymerizing reline resin products of 3 different thicknesses were tested. A cobalt-chromium edentulous maxillary cast was used to obtain 150 stone casts, 50 for each thickness of 1, 2, and 3 mm (n=10). Polystyrene record bases were filled with the autopolymerizing reline resin mixture and placed on the cobalt-chromium cast, which was mounted on a reline index, to serve as denture substitutes. Two thermal probes were used to monitor the temperature rise, which was recorded at 30-second intervals until no further increase was noted. Collected data were subjected to a 2-way ANOVA and the Tukey honestly significant difference test (alpha=.05). Results. The mean temperature increase for the chairside denture reline procedure ranged from 39.45 degrees C for the 1-mm thickness to 46.10 degrees C for the 3-mm thickness. The 2-way ANOVA found significant differences (P<.001) among the different reline resin materials and thicknesses tested. All materials produced an exothermic chemical reaction. An increase in thickness was always accompanied by an increased temperature. The Tukey honestly significant difference test found that the highest temperature increase for all 3 thicknesses occurred in the polymethyl methacrylate resin. Conclusions. The polymethyl methacrylate autopolymerizing hard denture base liner produced a significantly higher (P<.001) exothermic reaction than the other materials included in this study. One of the polyethyl methacrylate resins presented a higher exothermic reaction than the polymethyl methacrylate product at a 3-mm thickness, but the difference was not statistically significant. The polymethyl methacrylate resin presented the highest mean time to reach the maximum temperature for all 3 thicknesses.