Complete sealant retention after 15 years was observed in 22.0% of cases, and partial retention in 35.0%. The degree of sealant retention affected the occurrence of occlusal caries in sealed teeth. Reduction in caries after 15 years was 36.0% when all first molars were sealed and 54.0% when all posterior teeth were sealed. Caries developed in 7.4% of teeth with complete sealant retention, in 15.0% of teeth with partial sealant retention, and in 31.0% of teeth with complete loss of sealant.