Effect of Four Bleaching Regimens on Color Changes and Microhardness of Dental Nanofilled Composite

Objective. The purpose of this study was to compare the color changes and microhardness of a nanocomposite after four bleaching regimens. Materials. Twenty-five specimens (n = 25) were made with a nanocomposite resin (Filtek Supreme XT). The specimens were divided into five groups equally (n = 5): bleaching groups and control group, as follows: G1: artificial saliva at 37 degrees C; (control) G2: hydrogen peroxide (HP) at 7%; G3: hydrogen peroxide (HP) at 35%; G4: carbamide peroxide (CP) at 10%; G5: carbamide peroxide (CP) 35%. Color measurements were made with spectrophotometer using CIELAB color scale. The Vickers hardness (VHN) measurements were performed at the top surface. The data were analyzed with two-way Analysis of Variance. Results. DeltaE and VHN mean values into the groups were not statistically different, however, the VHN mean values before and after storage and bleaching showed statistically significant differences. Conclusion. Nanocomposite samples showed no significant alteration (color and microhardness) after bleaching. Thus, no replacement of restorations is required after bleaching.