Darkening of teeth is common in two cases: first, darkening of teeth caused by pulp necrosis; second, darkening of teeth caused by dental caries. It is necessary to go to the endodontic department of the hospital for detailed examination and check the vitality of the pulp to determine. If the tooth is black due to pulp necrosis, if not treated, it will easily cause periapical inflammation. It is recommended to do root canal treatment as early as possible, drill the pulp cavity, get rid of the necrotic pulp, prepare the root canal, rinse and disinfect, finally fill the root canal, and do crown restoration treatment after two weeks. If the tooth is black caused by tooth decay, it is suggested to fill the tooth as early as possible to avoid the possibility of pulpitis and even pulp necrosis if the tooth decay continues to aggravate. Drink more water, keep good oral hygiene habit and eat less sweet food.