Visual color compatibility of monochromatic and polychromatic composite resins under a combined bleaching protocol: an in vitro study

Restorative dentistry seeks to simplify aesthetic procedures while maintaining optimal color integration. This objective has catalyzed the development of monochromatic composite resins utilizing structural color technology. This study compared the color compatibility of a monochromatic resin (Omnichroma) and a polychromatic resin (Filtek Z350 XT) at various dental bleaching stages. Thirty Class V cavities were prepared in 15 human third molars (shade A3) and allocated into two groups: R1-P (polychromatic) and R2-M (monochromatic). Specimens underwent in-office bleaching (35% hydrogen peroxide) followed by at-home treatment (22% carbamide peroxide). Color compatibility was assessed at five time points (T1–T5) by two blinded evaluators. Statistical analysis (Kappa, Mann-Whitney, and Friedman tests; a=0.05) revealed no significant differences between groups at any stage. Longitudinal data indicated a transient decrease in compatibility during bleaching (T3) due to enamel dehydration, which stabilized post-rehydration (T5). In conclusion, the monochromatic resin demonstrated chromatic adaptation equivalent to the polychromatic material following post-bleaching stabilization.