Background and Aim: This study aimed to evaluate the effects of bleaching on surface roughness and color of two types of composite resins namely Gradia (hybrid microfilled) and Omnichroma (super-nano filled), subjected to two polishing methods.
Materials and Methods: In this in vitro study, 100 composite specimens (50 Gradia and 50 Omnichroma) were fabricated and divided into two groups for polishing with disc and bur systems. The baseline surface roughness and color parameters (L*, a*, b*) were recorded. The specimens were immersed in a tea solution for 24 days to simulate staining, followed by in-office bleaching with 38% hydrogen peroxide. Surface roughness and color parameters were re-measured post-bleaching. Statistical analysis was performed using repeated-measures ANOVA to assess the effects of bleaching, polishing method, and composite type (alpha=0.05).
Results: The interaction effect of polishing method and composite type on surface roughness was not statistically significant (P>0.05). A significant change was observed in ΔL after polishing compared with the baseline (P = 0.018), indicating an increase in lightness for Omnichroma. For Δa, Gradia composite polished with disc exhibited significant redness after immersion in tea (P=0.022), while Δb results showed that Gradia had a significant shift to yellowness across all stages (P<0.05).
Conclusion: The results showed that the surface roughness of both Gradia and Omnichroma composite resins increased after bleaching. Gradia exhibited more pronounced ΔE, particularly turning redder after immersion in tea, whereas Omnichroma displayed better color stability. These findings suggest that material selection and polishing methods are critical in maintaining esthetic outcomes in bleached composite restorations.