Effect of different bleaching procedures on the color match between the tooth and different composite resins

Objectives. Achieving a proper color-match between tooth and restoration after bleaching treatments is clinically challenging. Bleaching treatments could often result in a significant color mismatch with existing composite restorations, which remain unaffected by the whitening procedure. The aim of this in vitro study is to investigate the effect of different bleaching procedures on the color-match between tooth and restoration previously performed with several different composites. Materials and methods. The shade of 60 extracted sound teeth was instrumentally detected to fit specific parameters (VITA A2,A3,B3,C2-C4,D3,D4). A standardized class-V cavity (2x4x4mm) was performed buccaly, 1 mm above the cemento-enamel-junction. Teeth were randomized in 3 groups (n=20), according to the composite used for the restorations: Venus Pure Pearl (VP), Venus Pure Diamond (VD)Dflow, Venus Pure One Bulk (VB). CIEDE2000 color differences (ΔE00) between tooth and restoration were calculated, excluding specimens that did not respect perceptibility criteria (ΔE00 ≤1.8). Half specimens (n=10) were treated with Cavex Bite&White, a 25% in-office H2O2 gel (Cavex Bite&White), and half with Vivida Home Kit, a 6% home-use H2O2 gel (Vivida Home Kit,). An intraoral spectrophotometer detected CIELAB (L*,a*,b*), C* and h° color coordinates. Tooth – restoration ΔE00 and Whiteness Index (∆WID) were calculated 24h after the restoration (T0), 24h (T1) and 2 weeks after bleaching process (T2). Additionally, a visual analysis was performed at T0 and T2 by 16 dental professional observers (50% males and 50% females, with at least 5 years of experience) to evaluate the clinical color-match. Results. Instrumental evaluation revealed significant differences in ΔE00 values between T0, T1 and T2 within each group (adjusted p-values range from 0.00049 to 0.00834), while no significant differences were found between groups when compared at each individual timepoint. No significant WID differences were found between groups, except for VP treated with 6% H2O2 gel which showed a significant difference trend (adjusted p-values = 0,057) between T0 and T2. Conversely, the visual analysis conducted by the 16 observers at T0 and T2 demonstrated an improvement in the color-match between the tooth and the composite restorations after the bleaching procedures. Conclusions. While the instrumental data showed an increase in ΔE00 values, suggesting a worsening of the color-match between tooth and restoration after bleaching, the visual analysis revealed a clinical improvement in color integration. Since visual perception is more clinically relevant in dentistry than device-provided data, these findings highlight a significant discrepancy between spectrophotometric analysis and human clinical judgment, suggesting that the color-match after bleaching may be more successful than instrumental data indicate.