Comparative evaluation of different bleaching agents on the color stability, hardness and surface roughness of novel indirect esthetic restorative materials

Background To evaluate the effect of various bleaching agents of on color, surface roughness and microhardness of indirect restorative materials with different manufacturing methods. Methods Specimens of 3D-printed resin, milled-resin, and conventional resin were produced according to the manufacturer’s instructions (N = 50/group). After initial color, microhardness, and surface roughness measurements each group was divided into 5 subgroups: control group, 16% carbamide peroxide (Whiteness Perfect), 35% hydrogen peroxide (Whiteness HP Blue), 16% carbamide peroxide (Opalescence PF), and 40% hydrogen peroxide (Opalescence Boost). After bleaching procedure final color, microhardness and surface roughness of specimens were measured. Color change values were statistically analyzed with Kruskal-Wallis tests followed by Mann-Whitney-U tests (p < 0.05). The microhardness and surface roughness values were analyzed with two-way ANOVA and Tukey-HSD tests (p < 0.05). Results Material type and bleaching agent had a significant impact on color stability ( p  = 0.001). For all bleaching agents, conventional resin group showed the highest color change ( p  < 0.05). The type of indirect restorative materials had a significant impact on microhardness, while bleaching agents did not ( p  > 0.05). Conclusions Type of indirect restorative materials and bleaching agents had an impact on color, and surface roughness. Bleaching agents had no impact on microhardness of tested materials.