Comparison of transverse strength and dimensional variations between die stone, die epoxy resin, and die polyurethane resin.

This study compared transverse strength and dimensional variations of die stone, epoxy resin, and polyurethane resin. The polyurethane resin was tested unfilled, then filled with 20%, 40%, and 60% silica, by weight. Transverse strength was evaluated for five test strips for each material, and an original calibration plate technique closely simulating intraoral conditions was introduced to evaluate dimensional accuracy. Two series of five measurements for dimensional variations were recorded on each test strip. The first series was 15 minutes after removal from mold and the second series of 5 minutes a week later. The results were computed with a parametric ANOVA and Scheffe's test at 95% confidence level (p < or = 0.05). These results confirmed that die stone recorded the least dimensional change but was rigid and brittle, whereas epoxy resin and polyurethane resin had suitable mechanical properties including greater dimensional variations. Incorporating silica filler in polyurethane resins also reduced their transverse strength and sponsored minimal dimensional variations.