Effects of Water Pressure during Polymerization on Mechanical Properties of Autopolymerized Resins

Abstract

Purpose: This study evaluated the effects of water pressure on the mechanical properties and tensile bond strength of autopolymerized resins during polymerization at room temperature using a dental pressure pot with chair-side ease of handling.Methods: Four different autopolymerized resins (Unifast II, Unifast III, Provinice, and Miky Plus) were used. Specimens were fabricated by the brush-on technique. In the pressure group, specimens were polymerized in a dental pressure pot under 0.2 MPa water pressure at room temperature. In the non-pressure group, specimens were polymerized on bench. The 2 groups were compared for dimensional accuracy, 3-point bending, and tensile bond strength. Data were statistically analyzed by two-way analysis of variance (ANOVA) with Tukey’s multiple comparison test at a significance level of α=0.05.Results: Two-way ANOVA indicated that both resin and pressure had significant effects on the polymerization shrinkage rate (PSR). Interaction between resin and pressure was also significant. The PSR was lower in the pressure group than in the non-pressure group. The PSRs of Unifast II and Miky Plus were greatly improved by pressure polymerization. Significant differences in flexural strength were observed between the 2 groups. The flexural strength significantly increased under pressure. No significant differences in tensile bond strength were observed between the 2 groups.Conclusion: The dimensional accuracy and flexural strength of autopolymerized resins were significantly improved by the application of water pressure during polymerization. No significant changes in tensile bond strength were observed following pressure application at room temperature.