Sealants are a preventive treatment used mostly on the back teeth. In many teeth, the occlusal or chewing surface has fine grooves or pits where plaque accumulates. These grooves are too narrow to allow even one bristle of a toothbrush into them. These grooves can develop cavities over time. The dentist brushes on a coating that fills in and seals the grooves and pits, making it easy to brush off all the plaque and keep your teeth healthy.