The early decay of a tooth is usually painless. There are essentially three causes for tooth decay: (1) bacteria in the mouth; (2) food for bacteria, and (3) susceptibility to decay such as heredity or age. Tooth decay is a gradual process, which ordinarily begins with the outer layer of enamel and then penetrates into the dentin and perhaps even on into the pulp. There is a general consensus that the process of decay begins with plaque formation. Plaque is food debris and their products, which form a sticky, concentrated film that adheres to the teeth. Decay usually begins with a small-pitted area on the surface of the bone that enlarges to create a soft spot of partially dissolved enamel. The process is kept alive by the addition of sugar in our food that promotes bacterial growth. The longer this process is untreated, the greater the rate of destruction until the decay reaches the dentin, the main substance of the tooth.