Poor oral hygiene for teeth black common causes, as follows: 1, smoking, drinking tea: mostly by adults smoking or drinking tea after not timely cleaning of the oral cavity, resulting in smoke plaque, tea plaque deposited on the surface of the teeth caused by scaling or sandblasting treatment to clean up the surface of the teeth pigmentation, which restores the teeth itself color; 2, eating colored foods: such as chocolate, cola, etc., mostly in children, if children have completed the tooth replacement, the teeth can be cleaned by scaling or sandblasting treatment at about 12 years old. If a child has completed tooth replacement, he or she can undergo scaling or sandblasting at around 12 years of age to clean the surface of the teeth. In daily life, it is recommended that children brush their teeth in time after eating colored foods to avoid tooth color changes; 3. Tooth necrosis: the loss of blood supply due to tooth necrosis, which leads to tooth darkening. In this case, dental treatment should be carried out first, followed by crown restoration on the surface of the tooth to make the tooth look more beautiful.