effect of in-office carbamide peroxide-based tooth bleaching system on wear resistance of silorane-based and methacrylate-based dental composites

objectives: several studies have assessed the characteristics and properties of silorane-based composites and adhesive systems. considering the extensive application of tooth-whitening agents, possible deteriorative effects of tooth bleaching agents on these restorative materials must be studied. the aim of this study was to evaluate the effect of an in-office carbamide peroxide-based tooth bleaching agent on the wear resistance of a silorane-based and a conventional microhybrid dimethyl methacrylate-based dental composite with two different application times.   materials and methods: thirty cylindrical specimens were made of z250 and p90 dental composite resins (n=15 for each composite). samples made of each composite were divided into three groups (n=5) for immersion in an in-office bleaching agent (opalescence® quick 45%) for either three or eight hours or saline solution (control). wear tests were conducted after bleaching using a pin-on disk apparatus under the load of 40n at a constant sliding speed of 0.5 ms -1 for a sliding distance of 300 m. the samples were weighed before and after the wear test. repeated measures anova was used to statistically analyze the obtained data (α=0.05). results: there was a significant decrease in the weight of samples after the wear test (p<0.001). however, no significant difference was found among groups in the mean weight of samples before and after the wear test (p>0.05).  conclusion: bleaching for three or eight hours using 45% carbamide peroxide had no deteriorative effect on the wear resistance of z250 and p90 composites.