A tooth may appear gray because of pulpal necrosis, usually due to extensive caries penetrating the pulp, or because of hemosiderin deposited in the pulp after trauma, which may or may not have devitalized the pulp. Minocycline can cause permanent discoloration of fully formed teeth in adults. It also darkens bone, apparent as discoloration of the overlying gingiva and mucosa if they are thin. In ultraviolet light, affected teeth fluoresce a color characteristic of the specific tetracycline given, rather than white. In congenital porphyria, both the deciduous and permanent teeth are brown but fluoresce red from the pigment deposited in the dentin.
Congenital hyperbilirubinemia causes a yellowish tooth discoloration.
Defects in tooth enamel may be caused by the abnormal calcium metabolism associated with rickets, which results in enamel hypoplasia. A rough, irregular band forms in the enamel when abnormal calcification occurs. Any prolonged febrile illness during odontogenesis can produce a permanent narrow zone of chalky, pitted enamel, visible after the tooth erupts. Thus, the age at which the disease occurred and its duration can be estimated from the location and height of the band. Amelogenesis imperfecta, an autosomal dominant disease, causes severe enamel hypoplasia.