Your natural back teeth have cracks and grooves in it. It is very easy for food particles to remain even after good brushing since the toothbrush bristles can’t get into these cracks. The food particles can cause cavities. Sealants are simple procedure where a liquid is placed into the grooves and then becomes solid and protects blocks the cracks.
Sealants are one of the best ways to prevent future cavities on back teeth. CDC has shown that people without sealants are three times more likely to get future cavities!