Evaluation of genotoxicity and efficacy of at-home bleaching in smokers: a single-blind controlled clinical trial.

OBJECTIVE: This single-blind controlled study evaluated the genotoxicity and efficacy of at-home bleaching in smokers and nonsmokers. METHODS: We selected 60 patients with central incisors A2 or darker: 30 smokers (experimental group) and 30 nonsmokers (control group). The bleaching was carried out with 10% carbamide peroxide for three hours a day for three weeks. The color was evaluated using a shade guide, Vita Bleachedguide 3D-Master, at baseline, during bleaching (first, second, and third weeks), and one week and one month after bleaching. Smears were obtained with a moistened wooden spatula from marginal gingiva. All the cytologic smears were stained with Giemsa solution. From each slide, 1000 cells were examined under 40x magnification and where micronuclei (MN) were located, they were examined under 100x magnification. The change in shade guide units at the different assessment periods and the frequency of MN were subjected to a two-way repeated measures analysis of variance and Tukey test (alpha=0.05). RESULTS: In both groups we detected a whitening of approximately 4 to 5 shade guide units, without color rebound after one month (p>0.05). The frequency of MN was significantly higher in the experimental group than in the control group, regardless of the bleaching treatment (p>0.001). CONCLUSION: The efficacy of bleaching does not appear to be affected by the smoking habit. Additionally, at-home bleaching did not induce DNA damage to the gingival tissue during the bleaching period.