Background and objective: Chemical solutions are used to disinfect the teeth. They are usually used in combination with mechanical methods. Studies indicated that chemical solutions have a major role in the removal of microorganisms and microbial plaques. However, they cause physical and mechanical changes in acrylic resins such as changes in color, hardness and roughness of surface. Increasing surface roughness over time will increase the microbial and food particles adhesion to the acrylic surface, resulting in irritation and inflammation of the oral mucosa. Adding 1% TiO2 to acrylic can improve its properties. The objective of this study was to evaluate the effect of two denture disinfectant agents on the surface roughness of conventional acrylic resin and TiO2-reinfirced acrylic resin. Methodology: This research was a In-vitro study. The samples of this research included 60 acrylic resin samples in 2 groups (each group included 30 samples) and each group included 3 sub-groups (10 samples in each subgroup). Resin samples were made with heat-cured acrylic reinforced with 1% TiO2. They were immersed in three solutions of water, solution prepared with NatureDent tablet, and1% sodium hypochlorite for three periods of 30, 60 and 90 days. The disinfectant solution was replaced each day and this process was repeated. Then, the samples were washed with distilled water and placed in a container filled with distilled water to ensure uniformity of storage conditions. Then, the surface roughness test was performed on each sample. The data were analyzed using descriptive statistical methods and two-way ANOVA, one-way ANOVA, T-test and Tukey HSD test and through SPSS.17 statistical software. In this study, p value less than 0.05 was considered significant. Results: a significant difference was seen in surface roughness on the days 1, 30, 60 and 90, and the statistical value of 0.00 was reported in all 4 periods. By changing the type of disinfectant, the statistical value of the test on the day 1 and 30 did not show significant difference(p>.05). However, this value was reported 0.00 on the days 60 and 90, indicating a significant change in surface roughness(p <.05). In examining the simultaneous effect of resin type and disinfectant type, the statistical value of the test on the day 1 ,30 and 60 did not show significant difference(p>.05). However, on the day 90, indicating a statistically significant difference(p <.05). Moreover, the results showed that the rate of increase in sodium hypochlorite solution was higher than that of NatureDent and the rate of change in roughness in 1% TiO2-reinforced acrylic resin was less than that of conventional acrylic resin. Conclusion: By adding 1% TiO2 to heat-cured acrylic, the denture resistance to the change in surface roughness versus two solutions of sodium hypochlorite and a NatureDent disinfectant tablet can be increased. In addition, with increasing of time, the effect of the type of disinfectant solution on the roughness increases. This effect is lower in TiO2-reinfirced acrylic resin that in conventional acrylic resin.
