Effect of APF gel application time on enamel demineralization and fluoride uptake in situ.

This in situ crossover and blind study was conducted to investigate the effect of professional acidulated phosphate fluoride (APF) gel application time on the subsequent inhibition of enamel demineralization. During 3 phases of 28 days each, 15 volunteers wore palatal appliances containing 4 enamel blocks, which were subjected to 3 treatment groups: not treated (control) and pre-treated with APF gel for 1 or 4 min. Dental plaque was allowed to accumulate on the blocks and the appliances were immersed in 10% sucrose solution 3 times a day simulating a cariogenic challenge. After each phase, the blocks were removed to evaluate enamel demineralization and concentration of fluoride (F) remaining after the cariogenic challenge. F formed on enamel was determined in additional enamel blocks subjected only to APF gel application. APF gel was efficient in reducing enamel demineralization (p<0.05), irrespective of the application time (p>0.05). Also, the concentration of the F formed and retained on enamel was significantly higher after APF gel application (p<0.05), but the effect of time of application was not statistically significant (p>0.05). The results suggest that APF application for either 1 or 4 min is equally efficient to increase F concentration in enamel and reduce enamel demineralization.