Introduction & Objectives: Surface roughness affects beauty, hygiene, plaque retention and health of the gingival adjacent to the composite restoration. Many people use bleaching agents to beautify their teeth that may lead to changes in surface roughness. This study was designed to compare the silorane and methacrylate-based composites in bleached teeth.

 Materials & Methods: In this experimental study 48 composite resin disks were prepared and divided into 4 groups: P90, Z250, Z250XT and Z350XT (n=12). To determine the surface roughness, surface profile measurement of the samples was performed using profilometer. Samples of each diet group underwent 35% hydrogen peroxide in office whitening (Hpmax) in three 45-minute sessions one week apart. The secondary instances of surface profile was then measured. The data collected by the Kolmogorov-Smirnov test, one-way ANOVA, Tukey test and paired t- test at a significance level of 0.05 were analyzed using spss16. 

Results: There was a significant difference (P<0.05) in the surface roughness after bleaching on composite Z350XT with P90 and Z350XT with Z250. The surface roughness of all groups before and after bleaching showed a significant difference (P<0.05). 

Conclusion: The use of hydrogen peroxide 35% causes a significant increase in the surface roughness of composite P90, Z250, Z250XT and Z350XT.