Sealants are a protective coating that is applied to the deep crevices and grooves on the biting surface of the permanent back teeth. Due to the depth of the grooves, difficulty keeping these areas clean, and the modern diet, these grooves are at a high risk for developing cavities. Sealants fill in the grooves, decreasing the chances for the formation of cavities in these areas. While they do not protect teeth on the flat surfaces and in between, sealants have a long track record of helping to reduce cavities.
Since the placement of sealants requires a fairly high level of cooperation in order to be successful, they are usually not placed on the baby molars, especially when children are younger. Additionally, the grooves on baby molars are not typically as deep as the grooves on permanent teeth.