Decay often occurs on the chewing surfaces of the back teeth. These surfaces have deep grooves and pits. The bristles of a toothbrush (blue) cannot enter deep into these grooves to remove the plaque, or bacteria, within these grooves. Thus, bacteria lodged within these deep grooves (or fissures) can easily cause decay.
Sealants are thin coatings placed on the teeth to prevent decay. They are painless to place on the teeth and no drilling is done in the teeth.
They are often placed on the molars, premolars and even front teeth that may have grooves that may get easily decayed.
Fluoride is effective on the smooth surfaces of the teeth. So together, sealants and fluoride, help to prevent decay on all surfaces of the teeth.