The durability of cariostatic effect of school-based fluoride mouthrinsing was determined. Caries prevalence and incidence of 134 junior high school students (67 boys, 67 girls; fluoride group) who had participated in a fluoride mouthrinsing program (5times/week, 500ppm F) for 6 years in elementary school were compared with those of 222 students outside the program (control group) who had entered the same school at the same time.
Caries prevalence of the fluoride group was 27% (mean DMFT) lower than that of the control group 2 years after the end of the fluoride mouthrinsing program (p<0.001), and caries increment was 32% (new DMFT) lower in the 2nd to 3rd years of junior high school. Significant difference of caries incidence (mean DMFT increment) was observed between during and after fluoride mouthrinsing.
This result suggests that the cariostatic effect of fluoride mouthrinsing changed in a relatively short period after the end of the program. It is conceivable that such change was affected by caries increment of later erupted teeth, such as the second molars.