Black teeth are not a specific condition they are result of various bad habits and diet. The common causes of black teeth are smoking, tobacco chewing and caffeine. In the regions of Asia people have black teeth due to betel. Chewing betel gives brown color to the teeth. Poor dental hygiene can also cause teeth discoloration in old age. Many diseases can also cause teeth blackening by damaging enamel, the hard surface of teeth. One of the most common causes of teeth blackening is chemotherapy treatment in cancer patients. Some dental materials which are used to restore the teeth in old people can also give a black color to teeth. Because of aging the natural covering of teeth which is called enamel gets worn away due to this underlying layer dentine is visible which is yellow in color.