Effects of Dentifrices Differing in Fluoride Content on Remineralization Characteristics of Dentin in vitro

OBJECTIVES The aim of this study was to compare the caries preventive effect of highly fluoridated dentifrices and gels on sound dentin as well as on artificial dentin caries-like lesions. METHODS Bovine dentin specimens (n = 240), with 2 different surfaces each (1 sound surface [sound treatment (ST)] and one caries lesion [demineralized treatment (DT)]), were prepared and randomly allocated to one highly (6 × 120 min demineralization/day [H]) and one lowly cariogenic (6 × 60 min demineralization/day [L]) pH-cycling model. Treatments during pH-cycling (28 days) were: brushing 2×/day with: 0 ppm F [H0/L0], 1,450 ppm F [H1,450/L1,450], 2,800 ppm F [H2,800/L2,800], 5,000 ppm F [H5,000/L5,000], 5,000 ppm F plus TCP [H5,000+TCP/L5,000+TCP], and 12,500 ppm F [H12,500/L12,500] containing dentifrices/gels. Dentifrice/gel slurries were prepared with deionized water (1:2 wt/wt). Differences in integrated mineral loss (∆∆Z) and ∆ lesion depth were calculated between values before and after pH-cycling using transversal microradiography. RESULTS The correlation between ΔΔZDT and F- was strong for the highly (rH = 0.691; p < 0.001) and moderate (rL = 0.500; p < 0.001) for the lowly cariogenic model, indicating a fluoride dose-response for both. Significant differences for ΔΔZDT and ΔΔZST could be found between H0, H1,450, H5,000, and H12,500 as well as L0, L5,000, and L125,000 (p ≤ 0.046; analysis of covariance [ANCOVA]). Except for 0 ppm F-, no significant difference in ΔΔZST and ΔΔZDT could be found between the highly and lowly cariogenic model (p ≥ 0.056; ANCOVA). CONCLUSION For both pH-cycling conditions a dose-response for fluoride could be revealed. For elderly people with exposed root surfaces, the use of gels containing 12,500 ppm F instead of regularly (1,450 ppm F) or highly (5,000 ppm F) fluoridated dentifrices should be further investigated, as it offered higher caries-preventive effects in vitro.