Effect of heat treatment of polymethyl methacrylate powder on mechanical properties of denture base resin.

ABSTRACT

OBJECTIVES: The aim of this research was to investigate the effects of heat treatment of polymethyl methacrylate powder on mechanical properties of denture base resin. METHODS: PMMA powder was applied after heat treatment at 100°C for 2h (code HT100) or 130°C for 2h (code HT130). The test specimens were fabricated from autopolymerizing resin to investigate the flexural properties of denture base resin cross-linked with methacrylated dendrimer, the surface microhardness of PMMA beads, and the thickness of the swollen layer of PMMA beads. The specimens were autopolymerized, and all specimens were stored in 37°C water for 24h. Half of the specimens were immersed in 37°C water for an additional 6 months (water storage period 24h and 6 months). The flexural strength and flexural modulus (n=10/group) were measured with a three point bending test. Statistical analysis was performed using ANOVA and the Newman-Keuls test at a significance level of 0.05. RESULTS: Heat treatment and the water storage period had a significant effect on flexural strength. The flexural strength of HT130 showed significantly higher values than in other groups. The surface microhardness of PMMA beads of HT130 showed a significantly greater microhardness than other groups. The thickness of a swollen layer of PMMA beads of HT100 and HT130 was significantly decreased. CONCLUSIONS: The flexural strength and the surface microhardness were increased after heat treatment at 130°C. The thickness of a swollen layer of PMMA beads was decreased after heat treatment.