The chewing surfaces of the molar and premolar teeth have grooves — “fissures” — that make them vulnerable to decay. These fissures can be deep, are difficult to clean, and can be narrower than even a single bristle of a toothbrush. Plaque accumulates in these areas, and the acid from bacteria in the plaque attacks the enamel and cavities can develop.  Dental sealants provide extra protection for the grooved and pitted areas by providing a smooth surface covering over the fissured area.