A disease in which the mineralized tissues of the tooth undergo progressive destruction from the outside surface of the tooth. It is caused by bacteria that colonize the tooth surface and, under certain conditions, produce sufficient acids to demineralize the enamel covering of the tooth crown or the cementum covering the root, and then the underlying dentin. As the destruction of the dentin progresses, along with breakdown of the organic components, the bacteria invade the dead tissue and enter the pulp chamber. The pulpal tissue becomes infected and the typical toothache may ensue. The infection can ultimately destroy the pulpal tissue and extend out through the apical openings of the roots and into the surrounding periodontal tissues.