This study aims to verify the actual possibility of using silver diammine fluoride (SDF) in arresting enamel caries lesions on occlusal surfaces of primary molars in babies. Besides, the cost-efficacy and also parental acceptability of using SDF will be evaluated. For this, 100 babies 1-3 years will be examined and treated in a mobile dental unit, which will temporarily be parked in public schools of Barueri, Sao Paulo, Brazil. The caries diagnosis will be conducted using the International Caries Detection and Assessment System (ICDAS). Babies with initial lesions will be randomized concerning the treatment in Group A (SDF) and Group B (fluoride varnish). Participants will be examined in the baseline and followed by 6, 12, 18 and 24 months. As primary outcome, caries progression into dentine will be considered. Acceptability reported by parents after treatments, the time and estimated money spent for treating will also be collected. Social and biological data that could be related to efficacy of techniques will be also collected. Multilevel analyses will be performed to check which technique will be most effective and possible factors associated to its efficacy. Discomfort, acceptability and costs will be compared between/among the approaches used to arrest enamel caries lesions.