Effectiveness of different carbamide peroxide concentrations used for tooth bleaching an in vitro study

Objectives: This in vitro study evaluated the effectiveness of three carbamide peroxide concentrations used for tooth bleaching treatments. Material and Methods: Sixty bovine staining (baseline) and randomized into four groups (n=15), according to the bleaching agent concentration: distilled water (control), 10% (CP10), 16% (CP16) or 37% (CP37)carbamide peroxide. CP10 and CP16 were covered with 0.2 mL of the respective bleaching gels, which were applied on enamel surface for 4 h/day during two weeks. Samples of CP37 were covered with 0.2 mL of the bleaching gel for 20 min. The gel was light activated by two 40-s applications spaced by 10-min intervals. The gel was renewed and applied 3 times per clinical session. This cycle was repeated at 3 sessions with 5 days of interval between them. Tooth shade evaluations were done with a digital spectrophotometer at T0 (baseline), T1 (after 1-week of treatment) and T2 (1-week post-bleaching). Tooth shade means were statistically analyzed by Kruskal-Wallis and Friedman???s tests and color parameters were analyzed by two-way ANOVA and Tukey???s test (p<0.05). Results: At T1 and T2 evaluations, CP37 group showed lower shade mean change than CP10 and CP16 at T1 (p