In-office bleaching treatment effect over enamel microhardness from bulimic patients

Frequently, bulimic patients seek to improve their esthetic appearance by dental bleaching. Objective: considering that both bulimia and dental bleaching can alter dental structure and that there are different bleaching treatments, the aim of this study was to assess the effect of associating two demineralizing processes (in-office bleaching and bulimia) on the microhardness of tooth enamel. Methods: 30 fragments of included human third molars were used, and divided into 3 groups: G1 – simulated bulimia (0.01 HCl, 2x/day, 21 days); G2 – simulated bulimia and in-office bleaching treatment (38% hydrogen peroxide; weekly); G3 – in-office bleaching treatment. During the intervals, all fragments were kept individually in daily collected natural saliva at 37oC. Knoop microhardness tests (KHN, 25g, 5s) were performed before, during (7 and 14 days) and after treatments (21 days). Factorial ANOVA and Tukeyxs test were used to compare treatments (capital letters) and time (small letters). Results: as mean ± SD, Initial: G1=355.7±96.6Aa, G2= 342.6±81.8Aa and G3=282.2±94.6Aa; 7 days: G1=218.9±69.4Aab; G2=212.7±47.0Ab; G3=192.7±101.1Aab; 14 days: G1=191.3±38.3Ab; G2=200.4±48.7Ac; G3=250.3±54.6Aa; final: G1=146.6±22.8Ab; G2=146.5±16.6Ac; G3=146.9±17.2Ab. Conclusion: significant mineral loss occurs both after in-office bleaching treatment and/or bulimic simulation.