Sealants are used to fill in narrow grooves in a tooth that cannot be adequately cleaned by brushing. In some cases, the tooth structure has fine grooves or pits that accumulate plaque because the grooves are too narrow to allow even one bristle into them. To help prevent future cavities, the dentist seals the tooth. The sealant is a coating that seals the grooves and pits, helping to keep your teeth healthy.