RESUMEN
OBJECTIVE: To conduct an in vitro evaluation of the effect of casein-phosphopeptide and amorphous calcium phosphate with fluoride [CPP-ACPF] upon the calcium [Ca] and phosphorus [P] composition and morphology of dental enamel and dentin after the application of two bleaching agents: 37.5% hydrogen peroxide [HP]) and 35% carbamide peroxide [CP]. MATERIALS AND METHODS: The crowns of 40 extracted human teeth were divided into four groups (n=10 each). The crowns were sectioned along the cervical-incisal axis, and each half was embedded in acrylic resin, leaving a window 3mm in diameter to explore the enamel or dentin (according to the study group involved). Groups 1a and 1b corresponded to the two halves belonging to the same tooth and were treated with HP applied to enamel three times for 10min. Afterwards, CPP-ACPF was applied in group 1b for five minutes. The same procedure was carried out in groups 2a and 2b, but application was done on dentin. Groups 3a and 3b were treated with CP applied to enamel once for 30min. Posteriorly, CPP-ACPF was applied in group 3b for five minutes. Groups 4a and 4b were treated in the same way as groups 3a and 3b, but application was done on dentin. The morphological changes were evaluated using confocal laser scanning microscopy (CLSM), and the changes in Ca and P composition were assessed by environmental scanning electron microscopy coupled to a microanalytical system (ESEM+EDX). Comparisons between groups were made using the Kruskal-Wallis test, and Duncan test was applied for two-by-two comparisons, with a significance level of p<0.05. RESULTS: Both HP and CP produced similar changes in enamel morphology and produced no changes in dentin. Groups treated with CPP-ACPF after bleaching improved the percentage of Ca and P. Statistical significance was reached only in the case of the percentage of Ca in enamel (group 1b versus group 1a, p=0.01) (group 3b versus group 3a, p=0.03). CONCLUSIONS: The application of CCP-ACPF for five minutes on the enamel surface after tooth bleaching is effective in restoring the Ca lost as a result of the bleaching process, while their effect in dentin could not be demonstrated.