 A dental sealant is a thin coating that's painted on teeth. It's a quick, easy, and painless way to help prevent cavities in children. Sealants prevent the most cavities when applied soon after permanent molars come in. That's about age 6 for first molars and age 12 for second molars. Sealants can protect against cavities for up to nine years. They can be applied in dental offices or using portable dental equipment in community settings like schools.