Tooth decay refers to an area on a tooth that has been destroyed by acids created by bacteria in dental plaque. Plaque is a sticky material made of mucus and saliva, food particles, and bacteria. Even after a thorough cleaning, plaque begins to form within hours. The main cause of tooth decay is plaque. Bacteria in plaque feed mainly on simple sugars and starches in food.
Bacteria create an acid that gradually destroys the enamel of a tooth, forming a cavity.
Enamel is the outer, hard, glossy layer of the chewing surfaces of a tooth. This causes pain and the cavity gets bigger. Bacteria can next invade the exposed pulp at the center of the tooth and destroy the nerve. Early dental decay often causes no discomfort. After decay has destroyed much of the hard, outer portion of the tooth, you may get a toothache when you eat hot, cold, or sweet foods.