Fluoride dentifrice is effective in preventive dental caries but may cause fluorosis, especially in young children. Reducing the concentration of fluoride from the regular concentration of 1,000 parts per million (ppm) to 500 ppm can reduce the risk for fluorosis but increases the risk of caries. Adding tricalcium phosphate (TCP) to the dentifrices may improve the efficacy of remineralization possibly allowing for a lower concentration of fluoride to reduce the risk of fluorosis. We studied this to inform future caries prevention efforts in children. We immersed 40 sound primary incisors into demineralizing solution (pH=4.4) for 96 hours at 37°C to create demineralized lesions. The 40 teeth were then divided into 4 groups of 10 teeth each. Group A: control (treated with deionized water only); Group B: treated with fluoride dentifrice at a concentration of 1,000 ppm; Group C: treated with fluoride dentifrice at a concentration of 500 ppm and 500 ppm TCP, and Group D: treated with fluoride dentifrice at a concentration of 1,000 ppm and 500 ppm TCP. The teeth were each subjected to 7 days of pH-cycling and the studied dentifrice was applied for one minute, 3 times daily during the 7 day period. After the 7 day period the teeth were each sectioned and examined with polarized light microscopy. The depths of demineralized areas were measured using Image-Pro plus software. A pair t-test was used to compare lesion depths before and after dentifrice treatment. Differences in mean lesion depths within each group were analyzed using the One-way ANOVA and LSD tests; a 95% confidence intervals were calculated. The mean lesion depths in all the groups before dentifrice treatment were not significantly different (p=0.143). The mean demineralized lesion depths after dentifrice treatment were significantly different by group (p=0.00). The mean demineralized lesion depth in Group A significantly deeper than the other groups (p=0.00). Group D had the shallowest depth, significantly shallower than the other groups (p=0.006). There was no significant difference in the mean demineralized lesion depth between Groups B and C (p=0.478). The mean demineralized lesion depth changed significantly after dentifrice treatment in all the groups (p=0.00). Group A was significantly deeper (p=0.00) and groups B, C and D were all significantly shallow. Group D had the greatest reduction in mean demineralized lesion depth (p<0.05). The 1,000 ppm fluoride plus TCP dentifrice gave superior remineralization than the 500 ppm fluoride plus TCP and the 1,000 ppm fluoride dentifrice. The 500 ppm fluoride plus TCP gave the same remineralizing effect as the 1,000 ppm fluoride dentifrice. TCP enhances remineralization on primary enamel when added to fluoride dentifrice. Our results show if TCP is added to fluoride dentifrice a lower concentration of fluoride is needed to provide the same benefit as fluoride dentifrice with a higher concentration of fluoride, reducing the risk of fluorosis in children.