Objective: This study aimed to examine and compare the anti-caries effects of slightly acidic 1% NaF-HF gel when applied once or twice (7-day or 6-month interval) to mandibular first molars in 6- to 7-year-old children. Method and materials: This was a 1-year, multi-arm, placebo-controlled, double-blind, parallel-group randomized trial. In total, 1,077 schoolchildren from eight primary schools were allocated to one of the four study groups (group 1, single application; group 2, two applications with a 7-day interval; group 3, two applications with a 6-month interval; group 4, placebo control). The occlusal surfaces of permanent mandibular first molars were examined by three calibrated examiners who were blind to the group allocation at baseline and the end of the study. Caries reduction and prevented fraction was assessed.
Results: A total of 986 children completed the study. There was a statistically significant difference in the mean D1MFT increment across the groups (P < .001). The mean D1MFT increment was 0.37 in group 1 (single application), 0.18 in group 2 (two applications with a 7-day interval), 0.21 in group 3 (two applications with a 6-month interval), and 0.56 in the control group. The mean D2MFT increments (0.22 in group 1, 0.06 in group 2, 0.18 in group 3, and 0.50 in the control group) also showed a statistically significant difference across the groups (P < .001).
Conclusion: Subacidic 1% NaF-HF gel exerts a high preventive effect on caries (more than 40%) when applied twice at a 7-day interval in 6- to 7-year-old schoolchildren who do not use fluoride toothpaste in areas where drinking water is not fluoridated.