Sealants When teeth are developing, depressions and groves form in the chewing surfaces of the enamel. These features are called "pits and fissures". They are impossible to keep clean, because the bristles of a toothbrush cannot reach into them. Therefore, pits and fissures are ideal places for plaque and bits of food to become lodged. Placing a thin covering (a sealant) over the pits and fissures can reduce the risk of decay.