 Group A - semi-annual application of 12 SDF; Group B - annual application of 12 SDF; Group C - semi-annual application of 38 SDF; Group D - annual application of 38 SDF. The children will be followed for 36 months in their kindergartens until they enter primary school. Clinical examinations at 6-month intervals will be conducted to assess whether the caries are arrested. Information on confounding factors, such as oral hygiene habits and the use of other fluoride agents, will be collected through a parental questionnaire at the baseline and follow-ups. 