Effect of three concentrations of sodium fluoride dentifrices on clinical caries

Purpose: To assess whether the anti-caries effectiveness of three concentrations of fluoride dentifrice (placebo, 500 ppm F^- and 1450 ppm F^-) could be differentiated with small sample sizes in short time frames. Materials and Methods: A controlled fluoride (F) dose-response study was conducted in concurrence with a supervised school oral hygiene regimen to assess whether dentifrices with increasing fluoride levels could be differentiated with small sample sizes in short time frames. The study was a randomized, double-blind study conducted for a period of 21 months. Subjects (N=657 with ∼219 per group) were randomized to placebo dentifrice, 500 ppm F^- dentifrice or 1450 ppm F^- dentifrice treatments for the first 9 months of the study. Subjects in the placebo group were then switched to either 500 ppm F^- or 1450 ppm F^- dentifrice for the remainder of the study, while subjects in the fluoride groups continued with their original treatment assignments. A calibrated examiner measured visual-tactile caries as DMFS that was supplemented with a radiographic examination at baseline, 9 months and 21 months for each subject. Results: The mean caries increments at 9 months were 0.35 surfaces, 0.34 surfaces, and 1.28 surfaces for the 1450 ppm F^-, 500 ppm F^-, and placebo groups, respectively. The mean caries increments at 21 months were 0.21 surfaces, 0.26 surfaces, 1.75 surfaces and 1.90 surfaces for the 1450 ppm F ^-, 500 ppm F^-, placebo/1450 ppm F^-, and placebo/500 ppm F^- groups, respectively. The 500 ppm F- and 1450 ppm F^- fluoride dentifrices delivered statistically significantly (P< 0.05) lower DMFS scores than the placebo control dentifrice at 9 months, while at 21 months the 500 ppm F^- and 1450 ppm F^- fluoride dentifrices delivered statistically significantly lower DMFS scores as compared to the both the placebo/500 ppm F^- and the placebo/1450 ppm F ^- dentifrice groups. There was no evidence of a dose response (1450 ppm F^- < 500 ppm F^-) at 9 months or at 21 months. In this study, the effectiveness of the two fluoride dentifrices was observed at 9 months and these outcomes were still present at 21 months, confirming that caries benefits can be observed in time frames as short as 9 months with approximately 200 subjects per treatment group.