The interventional study has proven that varnish containing 5% NaF is highly effective in preventing early childhood caries in 3-year-old children in the community: After 18 months of intervention, early childhood caries lesions (d1, d2) decreased from 100.0% to 66.1%, the dt index decreased from 4.3% to 2.6% and the ds index decreased from 4.5% to 2.9%.