Surface roughness of different composite resins subject to in-office bleaching

This study used atomic force microscopy to evaluate the effects of an in-office dental bleaching protocol on the surface roughness of 3 resins: microfilled, microhybrid, and nanofilled. Two disks of each resin were prepared and evaluated. Twenty-four areas (5 x 5 µm) were scanned using an atomic force microscope. Then, each disk was treated with 35% hydrogen peroxide activated by a light emitting diode. After bleaching, the disks were scanned again. Data from the 24 areas before and after bleaching were evaluated qualitatively using topographical and 3-dimensional images, as well as profile lines. Quantitatively, roughness data (mean roughness and root mean square) were statistically evaluated using standard ANOVA and Student-Newman-Keuls tests (P < 0.05). The bleaching procedure increased roughness for each resin analyzed. Based on the results, it was concluded that in-office bleaching with 35% hydrogen peroxide-based gel significantly increased the surface roughness of microfilled, microhybrid, and nanofilled resins.