Sealants are typically applied to teeth as a preventive measure against tooth decay after the permanent teeth have erupted. However, sealants can be applied to healthy teeth. Dental Sealants last from three to five years, but it is fairly common to see adults with sealants still intact from their childhood. A dental sealant only provides protection when it is fully intact, so if your sealants come off, let your dentist know, and schedule an appointment for your teeth to be resealed.