If the tooth is black after filling, according to the specific reason, it can be remedied by secondary repair, crown repair or sandblasting and polishing. 1. Secondary repair: After filling a cavity and black, there may be secondary caries, which requires secondary repair, removing the original tooth repair, cleaning up the blackened caries, and then repairing the tooth. 2. Crown restoration: If the cavity is black after filling, and if there is a black situation, it means that the pulp of the tooth may have been necrotic. In this case, it is necessary to remove the filling of the filling, and then remedy the situation by root canal treatment, and finally, crown restoration of the tooth. 3. Sandblasting and polishing: Blackened teeth can be caused by poor dietary habits, eating foods with melanin, and bad habits such as smoking and drinking. In this case, teeth can be cleaned by sandblasting to remove the black deposits. To summarize, when people have a cavity filling and then black, they should seek medical attention to find out the cause, and then treat and repair the tooth according to the specific cause of the disease.