Good oral hygiene - brushing and flossing daily - and a healthy diet are the best way to prevent plaque build-up in the mouth. But even the most thorough brushing does not always reach the deepest indentations in the back teeth (molars). Dental sealants fill in these depressions, preventing bacterial formation that causes tooth decay and other damage. In a procedure that takes only a few minutes per tooth, the dentist cleans the tooth, applies an acid solution to roughen the surface, and bonds a plastic sealant to the tooth. A special light may be used to speed the hardening process. Sealants can help both adults and children, and may be re-applied every few years.