Effect of in-office bleaching agents on the surface roughness and morphology of different dental composites: an AFM study.

The aim of this study was to evaluate, using atomic force microscopy, the effect of two different bleaching agents on the modification of dental composites materials. This modification will be judged by analyzing the variation of surface roughness and surface morphology of two different composites: one containing nanoparticles and other consisting of microhybrid resin. The bleaching was performed by using two different concentrations of hydrogen peroxide: HP Blue (20% hydrogen peroxide) and Whiteness HP Maxx (35% hydrogen peroxide). Disks of Esthet X and Filtek™ Z350 composites were used. Atomic force microscopy was used for analyses of the same place of the sample before and after treatment. A total of 12 analyses were performed per group (n = 12). The samples were analyzed qualitatively by evaluating morphological changes in the images and quantitatively by using roughness parameters (Ra). Data were analyzed statistically using Kruskal-Wallis, Mann-Whitney, and Friedman tests (P < 0.05). Changes were observed both qualitatively and quantitatively only in the groups where Esthet X resin was used. The use of hydrogen peroxide bleaching agents caused changes only in the surface of microhybrid composites, with no changes being observed in the composite containing nanoparticles. Despite being even significant, these alterations are clinically slight and can be eliminated by polishing them.