Tooth decay, also known as dental caries, is the destruction of the tooth enamel. The tooth enamel is the hard, outer layer of the tooth. Tooth decay can affect anyone. Next to the common cold, tooth decay is next in terms of the most common diseases in our lifetime. But it has proven to be more concerning in children. According to the American Dental Association, tooth decay is the single most common continuing disease in children. It is more common than asthma, childhood obesity, and diabetes.