Abstract: Objective To assess the effect of topical fluoride varnish in prevention of first permanent molar caries of school-age children and provide evidence for formulating caries prevention strategies. Methods Using cluster random sampling method, in November 2014, 666 children of 6-7 years old in the first grade of primary school in Dahua County, Guangxi province were randomly selected and divided into two groups. From November 2014 to May 2017, the children in the test group were treated with fluoride varnish every six months, along with oral health education; whereas children in the control group were only given oral health education. In November of 2014, 2016, and 2017, oral examinations were performed on all subjects to collect data on the first permanent molars and conduct statistical analysis. Results After 2 years of intervention, the incidence of dental caries in the first permanent molar in the test group was lower than that in the control group, and the difference was statistically significant (P<0.05). After 3 years of intervention, there was a significant difference between two groups on the prevalence and incidence of caries, mean DMFT and mean DMFS (P<0.05). The incidence of maxillary and mandibular first molar, fissure and proximal surface caries of first permanent molars in the test group were lower than that of control group, but there was no significant difference in the incidence of proximal surface caries (P>0.05). Conclusion The topical application of fluoride varnish is effective in prevention of caries of first permanent molars, and longer the exposure time of fluoride varnish, better the effect of prevention.

Key words: Key words: fluoride varnish, the first permanent molar, caries prevention