A total of 254 children were examined 36 months after a single application of sealant. In 128 children, 201 permanent first molars were treated with Delton, and, in 126 children, 205 permanent first molars were treated with Nuva-Seal. Delton was completely retained on 80% of all paired permanent first molars, partially retained on 10%, and completely lost on 10% of the study teeth. Nuva-Seal was completely retained on 60% of all paired permanent molars, partially retained on 21%, and completely lost on 19% of the study teeth. Delton was 69% effective in preventing occlusal caries on permanent first molars three years after a single application. Nuva-Seal was 39% effective in preventing occlusal caries on permanent first molars three years after a single application. Both sealants have been shown to prevent dental caries on permanent first molars of children three years after a single application.