Effect of aging on mechanical properties of polymethyl methacrylate reinforced by nano zirconium or nano silver

Abstract Aim The purpose of this study was to evaluate the effect of aging process on the acrylic denture base reinforced by 5 wt% nano-zirconium (ZrO 2 ) or 5 wt% silver nanoparticles (AgNPs) regarding to flexural strength and surface hardness. Materials and methods A total of 45 heat-polymerized acrylic resin specimens were prepared with bar shape and were divided to three groups pure, modified with 5 wt% nano-ZrO 2 and 5 wt% AgNPs each group were subdivided into three subgroups according to immersion periods in artificial saliva ( n = 5). Flexural strength and surface hardness were measured after artificial saliva immersion at 37°C for 48 h, 3 and 6 months. One-way analysis of variance and Tukey multiple-comparison tests were used for data analysis ( P = 0.05). Results Flexural strength and surface hardness were improved by addition of 5 wt% nano-ZrO 2 or 5 wt% AgNPs as both groups compared to control group. Aging process for all groups showed significant decrease in flexural strength and surface hardness ( P < 0.001). Conclusion Addition of 5 wt% nano-ZrO 2 or 5 wt% AgNPs to polymethyl methacrylate showed an improvement in flexural strength and surface hardness and aging can significantly influence flexural strength and hardness of denture base resin even with nano-ZrO 2 or AgNPs addition.