The root of the tooth is a little black may be pigmentation, may also be caries, tetracycline and other conditions. 1. Physiological phenomenon: usually poor living and eating habits, often smoking, drinking alcohol, and often drink coffee, resulting in localized pigmentation of the teeth, which will appear in the root of the black a little bit of the situation. 2. Caries: usually due to the simultaneous presence of bacteria, diet, host factors. Patients often appear in the teeth white plaque, yellow-brown spots, etc., if not treated in time, but also gradually formed cavities, which can also appear in the root of the black a little bit of the situation. Some patients may also be accompanied by tenderness and other symptoms. 3. Tetracycline teeth: mainly due to the teeth in the development of mineralization period, taking tetracycline drugs. Patients often appear teeth staining, generally the onset of the initial tooth color to yellow-based, with the prolongation of the disease and age development, but also gradually changed to brown or dark gray, which can also be manifested as a bit of black root. It is recommended that patients with black teeth, according to the cause of the disease, under the guidance of the doctor to take reasonable treatment measures.