Effect of Water Storage on the Microhardness of Acrylic Resins

Objectives: The hardness of denture base is an important feature to resist wear. In this study, the Vicker′s microhardness (VMH) of heat-, chemical-, microwave- and visible light-cure acrylic resin denture base materials after 12 months of water storage was evaluated. Methods: 6 specimens for each heat, chemical, microwave and visible light polymerization method with a total number of 24 acrylic resin specimens were prepared. VMH measurements were made before and after storage in distilled water at 37°C for 1 day, 1 week and 1-12 months monthly. 5 indentations were made on each specimen and the average VMH value was calculated. Data was statistically analyzed with Kruskal-Wallis and Dunn′s multiple comparison tests (p≤ 0.05). Results: Highest VMH values were obtained from visible light-cure acrylic resin specimens except after 1 and 3 months of storage periods and lowest VMH values were obtained from chemical-cured acrylic resin specimens (p≤ 0.01). Heat-cured acrylic resin specimens had the highest VMH values at the end of 1 and 3 months of storage but the difference with visible light-cure resins was statistically insignificant (p>0.05). Conclusion: Considering the findings of this study it can be concluded that after water storage for 12 months, visible light cure resins are more resistant to wear than heat-, chemical- and microwave-cure resins.