Sealants are a preventative measure used to fill in the narrow grooves on a tooth that cannot be adequately cleaned by brushing. In some cases, the tooth structure has fine grooves or pits which accumulate bacteria and plaque. These may turn into cavities over time. A sealant is a clear material applied to the top surfaces (chewing surfaces) of those teeth that do not already have a cavity or a filling. Sealants act as barriers to seal the deep grooves and pits on your back teeth (molars and premolars), preventing cavities from developing.