Color stability and staining susceptibility of direct resin-based composites after light-activated in-office bleaching

This study evaluated color stability and staining susceptibility of five direct resin-based composites (RBCs) subjected to light-activated in-office bleaching with 40% hydrogen peroxide (HP). The test materials included 5 RBCs, which consisted of one nano-filled, one sub-micron, one bulk-filled, and two nano-hybrid RBC types. Ten disc-shaped specimens of each RBC were fabricated and divided into bleaching (BLE) and non-bleaching (CON) groups (n = 5 for each group). Specimens were then immersed in red wine solution over 4 h. A spectrophotometer was used to obtain Commission Internationale de l’Eclairage (CIE) L*a*b* parameters for each of the following periods tested: before bleaching (T_BA), after bleaching (T_BL), and after staining (T_ST). Color stability and staining susceptibility were evaluated using two metrics, CIEDE2000 color differences (∆E₀₀ ) and whiteness variations using the whiteness index (∆WI_D). Data were analyzed using repeated measures two-way analysis of variance (ANOVA) (α = 0.05). Statistically significant and clinically unaccepted ∆E₀₀ and ∆WI_D were observed for all tested specimens between T_BA and T_BL . The nano-hybrid type RBCs showed the highest discoloration among materials after bleaching treatment. The BLE group exhibited significantly higher ∆E₀₀ and ∆WI_D than the CON group for all the tested RBCs between T_BA and T_ST . The sub-micron type RBC showed the highest discoloration among materials after immersion in the red wine. Conclusion. The light-activated in-office bleaching with 40% HP’s influences on color and whiteness index were material-dependent. The use of bleaching treatment also increased the susceptibility to red wine for all RBCs.