RESUMO
Objective: To evaluate the progression of caries around orthodontic brackets after the enamel has been exposed to lacteal products containing probiotics. Methods: Orthodontic brackets were bonded to the enamel surfaces. The test specimens were randomly divided into six groups: G1-negative control; G2-positive control, exposed to culture environment only (without microorganisms); G3-exposed to the cariogenic environment and the fermented cow's milk without probiotic; G4-exposed to the cariogenic environment and fermented cow's milk with probiotic; G5-exposed to the cariogenic environment and yogurt without probiotic; and G6-exposed to the cariogenic environment and yogurt with probiotic. The groups were placed in brain heart infusion medium, supplemented with 2% sucrose and with 1x106 cells/ml of Streptococcus mutans and Streptococcus salivarius (ATCC). The Shapiro-Wilk, Levene, Student t, Kruskal-Wallis, and Mann-Whitney tests were used. Results: all groups exposed to the ATCC strains showed lower final microhardness, compared to the negative control (p0.05). Conclusions: Lacteal products are not able to prevent the progression of caries around orthodontic brackets.