To evaluate the effect of a combination of fluoride dentifrice and acidulated phosphate fluoride (APF) on enamel with incipient caries lesions.Bovine dental enamel blocks with artificial caries lesions were divided into four treatment groups and submitted to a pH-cycling model: (1) Placebo non-fluoridated dentifrice (PD); (2) Fluoridated dentifrice (FD), 1,100 ppm F; (3) APF (12,300 ppm F, pH 3.5) + PD; 4) APF+FD. APF was applied to enamel blocks of groups APF+PD and APF+FD before the pH-cycling regimen and all of them were exposed to dentifrice during the cycling.The results showed that 61-81% of the fluoride previously deposited in enamel by APF was released to the media during the pH-cycling. The final concentration of fluoride in enamel in the group APF+PD was lower than that before the cycling (P 0.05). FD treatment was significantly more efficient than PD in rehardening the enamel surface and increasing the hardness of the caries lesions. APF+PD treatment was not more efficient than PD in increasing enamel hardness and an additive effect of APF+FD was not observed.