The effects of treated time of acidulated phosphate fluoride solutions on enamel erosion

The aim of this study was to reevaluate the treatment time of topical application of acidulated phosphate fluoride (APF) solution. Bovine intact enamel was treated with APF solution (pH 3.5, 9,000 ppm F) for 0, 1, 2, 3, 5, and 10 min. Fluoride penetration into the enamel was determined using electron probe micro analyser (EPMA), and the hardness of APF-treated demineralized enamel was evaluated via the micro Vickers technique. Micro Vickers hardness (HV) was significantly different in enamel treated with APF for 1 min and that treated for >2 min, and also between enamel treated for 2 and that treated for 3 min in samples demineralized for 2 h. No significant difference in the surface roughness (Ra) by confocal laser scanning microscopy was evident at the 3 and 5 min time points. The results of the EPMA analysis, HV, and Ra tests suggest a clinically beneficial effect of APF when applied for 3 min.