ABSTRACT
Aim: This study investigated the effect of an in-office bleaching technique on lightness, color and surface roughness of two commercially available materials: a resin-modified glass-ionomer cement and a nanohybrid resin composite. Methods: Twelve disk-shaped specimens were prepared with both materials. The samples were bleached with 35% hydrogen peroxide. Bleaching was tested initially onto a smooth surface and later onto a polished one of the same specimens. The effect of the treatments on lightness and color was verified with a spectrophotometer. Surface roughness was measured with a digital surface roughness tester. The data were statistically analyzed by repeated measures ANOVA and post hoc Tukey's test (alpha = 0.05). Results: Significant variation in lightness and color was observed on the resin-modified glass-ionomer cement after the first bleaching procedure. Roughness increased significantly only after polishing the resin-modified glass-ionomer cement surface. Composite color variation was evident in the last observation period, but roughness and lightness variation due to bleaching and polishing was not significant. Conclusion: The bleaching treatment caused significant color alterations on the materials tested. This study observed that the application of in-office bleaching onto the glass-ionomer cement promoted clinically observable color alteration, and polishing after bleaching is contraindicated for this material. (AU)