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 dental slabs (6x6x3 mm) were obtained, sequentially polished, submitted to artificial 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, tooth shade was significantly lighter than at baseline for all treatment groups, considering the color parameters δl*, δa*, δb*, δe* (p<0.001) or tooth shade means (p<0.001). cp37 group showed lower shade mean change than cp10 and cp16 at t1 (p<0.01), but this difference was not statistically significant at t2 (p>0.05). conclusions: one week after the end of the treatment, all carbamide peroxide concentrations tested produced similar tooth color improvement.