Dose Response Efficacy of Sodium Fluoride Dentifrice at 9 and 21 Months with Supervised Brushing

Objective: This was a randomized, double-blind study conducted for 21 months (mos.) 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. Methods: Subjects (N=644, ~215 per group) with a mean age of 10.4 years old (9-12 y.o.) used a placebo, an 1100 ppm F or a 2800 ppm F dentifrice for the first 9 mos. of the study. Subjects in the placebo group were then switched to either 1100 ppm or 2800 ppm F dentifrice. Subjects in the fluoride groups continued with their original treatment. Three calibrated examiners measured visual-tactile caries as DMFS that was supplemented with a radiographic examination at baseline, 9 and 21 mos. Results: The results are consistent with previous results reported for NaF dentifrices. For all examiners, the 1100 ppm and 2800 ppm F dentifrices delivered statistically significantly (p<0.05) lower DMFS scores than the placebo at 9 mos., while at 21 mos. the 1100 ppm and 2800 ppm F dentifrices delivered statistically significantly lower DMFS scores versus both the placebo/1100 ppm F and the placebo/2800 ppm F dentifrice groups. One examiner observed a directional (p=0.11) dose response (2800 ppm F < 1100 ppm F) at 9 mos., while at 21 mos. all three 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. Conclusion: The effectiveness of the two fluoride dentifrices was observed at 9 mos. These outcomes were still present at 21 mos., confirming that caries benefits can be observed in time frames as short as 9 mos. with approximately 200 subjects per treatment group.