Imperfections in plaster surfaces caused by the release of hydrogen gas of polyvinylsiloxane impression materials

Abstract

Purpose: The purpose of this study was to evaluate the number of bubbles of hydrogen liberation from different polyvinylsiloxane impression materials. Material and Methods: A metallic stainless steel jig containing six receptacles, like trays, was constructed to accommodate the impression materials. The molds were poured immediately, and at 1 hour, 12 hours and 24 hours in order to evaluate the number of bubbles present in each sample. Each sample was made of improved stone (type IV), totaling 48 samples for each polyvinylsiloxane impression material. After setting, the surface of each sample was inspected under a light microscope at 40x magnification and the number of bubbles was recorded. Results were submitted to statistical analysis by ANOVA and Tukey Test (p=.05). Results: ANOVA test showed statistically significant differences among the polyvinylsiloxane impression materials, as determined by the number of bubbles (p<.05). The Tukey test showed statistically significant differences among the three groups (p<.05). Conclusions: Statistical differences were found between addition silicone with regard to the ideal time to wait for the plaster cast, showing that Aquasil results in fewer bubbles in plaster, followed by the President and Simply Perfect samples.