The Effect of Staining Beverage on Color Alteration During In-office Tooth Bleaching

Sixty-three eligible participants (25 males and 38 females, mean age 26.5 years) with at least one maxillary tooth demonstrating shade A3 or darker will be recruited and randomly allocated into 3 groups (n = 21), according to the different staining beverage used in this clinical trial: Coffee for group C, Tea for group T, and distilled water for group W. All participants will receive in-office tooth bleaching with 40% hydrogen peroxide (Opalescence Boost PF 40%) for the maxillary anterior teeth (2 sessions, with a 1-week interval). The participants will be instructed to use only the provided beverage rinses for 30 seconds, four times daily. Colour parameters (CIE L\*, a\*, b\*) will be measured with a spectrophotometer (Vita Easyshade Advance 4.0) at baseline (T1), after the first bleaching session (T2), after the second bleaching session (T3), 1 week after the completion of in-office bleaching (T4), and 3 weeks after the completion of in-office bleaching (T5). The colour differences (ΔE) and whiteness index (W) will also be calculated. The data will be statistically analysed through repeated ANOVA and Tukey's test (α = 0.05).