Friction and Wear of Polymethyl Methacrylate Reinforced by Silica and Zirconia Nanoparticles as Dental Materials

In this study, unfilled PMMA and two groups of specimen composites of polymethyl methacrylate (PMMA) were investigated. The first group was reinforced with different contents of SiO2 nanoparticles ranging from 2.5 wt. % to 15 wt. % in order to obtain the optimum composition of the mixture that maintains the excellent tribological properties over that of the unfilled PMMA. The second group was prepared by adding zirconia (ZrO2) nanoparticles of content ranging from 2.5 % to 7.5 % to the composite containing 7.5 wt. % SiO2 nanoparticles. The effect of reinforcing PMMA with silica and zirconia nanoparticles on the wear and friction was investigated under dry sliding conditions, constant sliding velocity of 2 m/s and different applied normal load values, 5, 10, 15, 20 and25 N. The time of experiment was 600s. Based on the experiments carried out in the present work, it was found that wear resistance and friction coefficient of the composites were significantly influenced by SiO2 and ZrO2 nanoparticles contents. The lowest wear value in (PMMA/SiO2 nanoparticles) composite was obtained for 7.5 wt. % of silica nanoparticles, while for PMMA/SiO2 and ZrO2 nanoparticles was reported for 7.5 wt. % of silica and 5 wt. % of zirconia nanoparticles.