A dental sealant (also called a pit and fissure sealant) is a plastic, professionally-applied material that is put on the chewing surfaces of children's back teeth to prevent cavities. Sealants provide a physical barrier so that cavity-causing bacteria cannot invade the pits and fissures on the chewing surfaces of teeth.

First permanent molars erupt into the mouth at about age 6 years. Placing sealants on these teeth shortly after they erupt protects them from developing caries in areas of the teeth where food and bacteria collect. If sealants were applied routinely to susceptible tooth surfaces in conjunction with the appropriate use of fluoride, most tooth decay in children could be prevented.