Estimation of optimal amount of fluoride dentifrice for adults to prevent caries by comparison between fluoride uptake into enamel in vitro and fluoride concentration in oral fluid in vivo.

Fluoride dentifrice has been accepted widely for use in caries prevention and its effectiveness has been confirmed. In order to enable the use of fluoride dentifrice effectively in daily brushing, the present study was performed to examine the relationship between fluoride uptake and the amount of fluoride dentifrice used and brushing time for adults. We examined the relationship between fluoride uptake into the surface layer (4-6 microm)of enamel and the active fluoride concentration in vitro and the relationship between the amount of fluoride dentifrice (1,000 ppmF) used and the fluoride concentration in oral fluid in vivo. It became clear that fluoride uptake into the enamel was increased at the concentrations of 300 ppmF or more. Fluoride uptake at 300 ppmF was increased for 2 min and became saturated thereafter. The results of the relationship between the fluoride concentration in the oral fluid and the amount of fluoride dentifrice used indicated that the amount of dentifrice that could maintain the mean fluoride concentration at 300 ppm or more for 2 min was 1.0 g or more. From these results, the recommended amount of fluoride dentifrice (1,000 ppmF) is 1.0 g or more for adults.