It is of clinical importance to arrest the development of approximal caries at an early stage. The potential for initial caries to develop into manifest lesions has motivated studies on the use of sealants to arrest the progression of caries on both occlusal and approximal tooth surfaces.

Therefore, the aim of the present study was to follow-up and examine after 3.5 years, the efficacy of sealing caries-free or non-cavitated mesial surfaces of first permanent molars abutting lesions on the distal surfaces of second primary molars. The null hypothesis tested here was that preventive and therapeutic sealants do not prevent the development or slow the progression of dental caries over a period of 3.5 years in comparison to non-sealed control surfaces.

The study population comprised 121 schoolchildren aged 8 to 10 years in a high-caries community in Valparaiso, Chile. They were examined clinically and radiographically, divided into 3 groups, and treated accordingly: children in Group A had no carious lesions on the approximal surfaces of 05d-6m and received no sealants; those in group B had active caries on 05d and received a preventive sealant on the caries-free 6m; and those in group C had active caries on 05d with an initial active lesion on 6m and received a therapeutic sealant on 6m. After 3.5 years, standardized follow-up radiographs were obtained for the children that remained.

Inclusion Criteria:

• children with high rate of caries in the primary dentition
• active caries on the distal surfaces of the second primary molars at least on both sides of the mouth
• children with no lesions on the adjacent tooth surfaces on the second primary and first permanent molars were included as a general control group

Exclusion Criteria:

• children using medication containing sucrose or with a negative effect on salivary flow
• children using orthodontic devices
• children who refuses to participate