Plaque develops when foods containing carbohydrates (sugars and starches), such as milk, soft drinks, raisins, cakes, or candy are frequently left on the teeth. Bacteria that live in the mouth thrive on these foods, producing acids as a result. Over a period of time, these acids destroy tooth enamel, resulting in tooth decay. Plaque can also develop on the tooth roots under the gum and cause breakdown of the bone supporting the tooth.