The chewing surfaces of back teeth are not completely flat, but have pits and fissures which allows for food debris stagnation and bacterial increase. As cleaning of these areas is difficult even with the toothbrush, the germs, and the acids that are continuously produced provoke very rapidly dental caries.

Preventive fillings –sealants- come and fill these deep grooves of teeth smoothing the occlusal surface and making the cleaning with the toothbrush easier and more effective. It has been found that decay most usually develops in the first years after the appearance of teeth in the mouth. Therefore, preventive fillings –sealants- should be placed after the eruption of first molars and premolars in the mouth during childhood.