Correlation Among Methods to Measure Tooth Color in Clinical Trials Evaluating Tooth Bleaching

Abstract

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. Methods: 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 ΔE. Conclusion: Despite the weak/ moderate correlation among the methods used to measure tooth color, all methods showed similar results of tooth bleaching effectiveness.