Tooth Bleaching Effects on Colour Matching of Single-Shade Composite Restorations

Background: Tooth bleaching is a common cosmetic procedure, but it can result in colour mismatches with existing resin composite restorations. However, single-shade composite resins are designed to adapt to the colour of bleached teeth, potentially eliminating the need to replace restorations. Objective: To evaluate the effect of tooth bleaching on colour matching of single-shade resin composite restorations using instrumental and visual assessments. Methods: Round restoration preparations on the buccal and palatal surfaces of intact molars were restored with Charisma Diamond One or Palfique Omnichroma composite resins. Colour measurements were taken using a cell phone and image- processing software before and after restoration and again after 3 applications of a 35% hydrogen peroxide bleaching agent. Colour changes were calculated using whiteness (WID) and CIELAB colour difference (Delta E00) indexes. Visual assessments of colour match were also conducted by evaluators. Results: Both restorations and enamel exhibited comparable WID values after bleaching, and no significant changes in Delta E00 values were observed. However, evaluators assigned better colour matches to unbleached restorations. Conclusion: Instrumental colour measurements indicated that tooth bleaching did not significantly affect the colour match of single-shade resin composite restorations. However, visual assessments revealed poorer colour matching after bleaching.