RESUMO
OBJECTIVE: This study attempted to clarify the mechanisms of action of fluoridated acidic liquid dentifrices against dental caries. DESIGN: In the in vitro leg, enamel specimens were submitted to a pH-cycling model, treated with distinct dentifrices (0, 550 µgF/g pH 4.5 and pH 7.0, 1100 or 5000 µgF/g pH 7.0) and analyzed using hardness. Alkali-soluble fluoride (F) deposition was quantified on pre-demineralized specimens treated with the dentifrices. In the clinical leg, 2-to-4-year-old children who had been using liquid dentifrices for 6 months (550 µgF/g pH 4.5 or pH 7.0 or 1100 µgF/g pH 7.0) had their plaque samples collected 5 and 60 min after the last brushing. Fluoride uptake in whole plaque was evaluated. RESULTS: The reduction of the pH had a partial preventive effect on subsurface hardness loss only. [F] had a significant influence on the deposition of fluoride, surface and subsurface hardness loss. In vivo, the reduction of the pH was able to significantly increase plaque F uptake, leading to similar levels as those found for the neutral dentifrice containing twice [F]. CONCLUSION: The results obtained from in vitro studies whose design does not include the presence of dental plaque should be interpreted with caution.
