The chewing surfaces of back teeth are rough and uneven because they have small pits and grooves. Food and germs can get stuck in the pits and grooves and stay there a long time because toothbrush bristles cannot brush them away. Germs in the mouth use the sugar in food to make acids. Over time, the acids can make a cavity in the tooth. Sealants are thin, plastic coatings painted on the chewing surfaces of the back teeth. They keep out food and germs. The most important reason for getting sealants is to avoid tooth decay.
Source: National Institutes of Health
Anatomy, Patient Education
October 21, 2015