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

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 degrees C for 2 h (code: HT100) or 130 degrees C for 2 h (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 degrees C water for 24 h. Half of the specimens were immersed in 37 degrees C water for an additional 6 months (water storage period: 24 h 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 degrees C. The thickness of a swollen layer of PMMA beads was decreased after heat treatment. (C) 2014 Elsevier Ltd. All rights reserved.