Objective: This study aimed to assess possible differences in results provided by two
shade guides and a spectrophotometer used to measure the color changes during tooth bleaching.
Method: Fifty-six patients underwent two sessions of in-office tooth bleaching with a 35% hydrogen
peroxide with a week of an interval between them. The color evaluation was performed using shade
match with two guide scales (Vita Classical, and Vita Bleach Guide) and a spectrophotometer providing
CieLab data. The color was assessed at baseline and 7 days after each session, and 30 days
after the last session. Data from scales were arranged in scores according to lightness (lowest to
highest) and the color changes were calculated based on baseline data. For CieLab data, ΔL, Δa, Δb,
and ΔE were calculated for each assessment time. Differences between the color changes observed
in each session were assessed by Wilcoxon test (α = 0.05). Friedman`s test and One-way repeated
measures ANOVA were used to analyze color changes among the assessment times. Spearman`s test
was used to evaluate the correlation between the shade guide scores and data from Cielab.
Results: All methods of color measurement demonstrated any additional effect of second bleaching
session on color change, and stable color after 30 days (p < 0.001 for all methods). Both shade guide
scales presented low correlation coefficients with ΔL, and moderate coefficients with Δb, Δa, and
Conclusion: Despite the weak/ moderate correlation among the methods used to measure tooth
color, all methods showed similar results of tooth bleaching effectiveness.