In vitro Fluoride Uptake in Human Dental Enamel from Four Different Dentifrices

The in vitro fluoride uptake in human dental enamel treated with four different dentifrices was evaluated using a standardized technique. The fluoride concentration in two symmetrical areas of buccal surfaces of newly erupted premolars was analyzed in eight subsequent layers. One of the areas was treated with the dentifrice and the other served as a control. Fluoride gradient curves were computed for the two areas and the differences in the fluoride concentration at various distances from the enamel surface was calculated. Application of a dentifrice resulted in a small increase in the fluoride concentration of the enamel surface. After 1 h of treatment, however, the fluoride uptake was confined to the outer 5 μm of the enamel surface. No definite relationship was found between the fluoride ion activities in the dentifrice slurries applied to the tooth surface and the fluoride uptake. The small fluoride uptake in the enamel from the dentifrices, containing fluoride, may possibly be one reason for the moderate caries reduction obtained by daily use of fluoride-containing dentifrices.