Dose response efficacy of sodium fluoride dentifrice at 9 and 21 months with supervised brushing.

PURPOSE To assess whether a fluoride dose response could be detected with a relatively small sample size in a short duration using a novel randomized, double-blind study design. METHODS Subjects (N = 644, with approximately 215 per group) with a mean age of 10.4 years old (9-12 years old) used a placebo dentifrice, an 1100 ppm F dentifrice or a 2800 ppm F dentifrice for the first 9 months of the study. Subjects in the placebo group were then switched to either 1100 ppm or 2800 ppm F dentifrice for the remainder of the study, while subjects in the fluoride groups continued with their original treatment assignments. Three calibrated examiners 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 results of this study are consistent with the previous results reported for sodium fluoride dentifrices. For all examiners, the 1100 ppm and 2800 ppm fluoride dentifrices delivered statistically significantly (P < 0.05) lower DMFS scores than the placebo control dentifrice at 9 months, while at 21 months the 1100 ppm and 2800 ppm fluoride dentifrices delivered statistically significantly lower DMFS scores compared to the both the placebo/1100 ppm and the placebo/2800 ppm dentifrice groups. In addition, one of the three examiners observed a directional (P = 0.11) dose response (2800 ppm F < 1100 ppm F) at 9 months, while at 21 months all three examiners observed evidence of a dose response, with one examiner observing a statistically significant difference between 1100 ppm and 2800 ppm F. Caries scores on occlusal surfaces provided the strongest evidence of an 1100 ppm F vs. 2800 ppm F difference.