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 which accumulate plaque, not because the person doesn't brush, but because they're too narrow to allow even one bristle into them. These grooves or fissures can develop decay over time. So the dentist will brush on a coating that seals the grooves and pits, making it possible to brush off all the plaque and keep your teeth healthy. Sealants are usually placed on the permanent molars when they first erupt into a child's mouth.The first molars usually erupt around the age of six, and the second molars around the age of twelve, so the dentist may advise sealants at these ages.