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  • Title: Effect of microwave sterilization and water storage on the Vickers hardness of acrylic resin denture teeth.
    Author: Campanha NH, Pavarina AC, Vergani CE, Machado AL.
    Journal: J Prosthet Dent; 2005 May; 93(5):483-7. PubMed ID: 15867760.
    Abstract:
    STATEMENT OF PROBLEM: Acrylic resin denture teeth soften upon immersion in water, and the heating generated during microwave sterilization may enhance this process. PURPOSE: Six brands of acrylic resin denture teeth were investigated with respect to the effect of microwave sterilization and water immersion on Vickers hardness (VHN). MATERIAL AND METHODS: The acrylic resin denture teeth (Dentron [D], Vipi Dent Plus [V], Postaris [P], Biolux [B], Trilux [T], and Artiplus [A]) were embedded in heat-polymerized acrylic resin within polyvinylchloride tubes. For each brand, the occlusal surfaces of 32 identical acrylic resin denture posterior teeth were ground flat with 1500-grit silicon carbide paper and polished on a wet polishing wheel with a slurry of tin oxide. Hardness tests were performed after polishing (control group, C), after polishing followed by 2 cycles of microwave sterilization at 650 W for 6 minutes (MwS group), after polishing followed by 90-day immersion in water (90-day Wim group), and after polishing followed by 90-day storage in water and 2 cycles of microwave sterilization (90-day Wim + MwS group). For each specimen, 8 hardness measurements were made and the mean was calculated. Data were analyzed with a 2-way analysis of variance followed by the Bonferroni procedure to determine any significance between pairs of mean values (alpha=.01). RESULTS: Microwave sterilization of specimens significantly decreased (P <.001) the hardness of the acrylic resin denture tooth specimens P (17.8 to 16.6 VHN), V (18.3 to 15.8 VHN), T (17.4 to 15.3 VHN), B (16.8 to 15.7 VHN), and A (17.3 to 15.7 VHN). For all acrylic resin denture teeth, no significant differences in hardness were found between the groups MwS, 90-day Wim, and 90-day Wim + MwS, with the exception of the 90-day Wim + MwS tooth A specimens (14.4 VHN), which demonstrated significant lower mean values (P <.001) than the 90-day Wim (15.8 VHN) and MwS (15.7 VHN) specimens. CONCLUSIONS: For specimens immersed in water for 90 days, 2 cycles of microwave sterilization had no effect on the hardness of most of the acrylic resin denture teeth.
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