The black decay of tooth root often indicates serious caries, patients should go to hospital immediately to avoid the acute inflammation caused by the massive growth of bacteria. Through imaging examination, it can be judged whether the blackened and decayed part involves the pulp, and according to different conditions, there are generally the following treatment measures: 1.Bedding treatment: Generally, if the root length is sufficient and the pulp is not involved, it can be treated by bedding restoration, and most patients can complete the restoration at one time; 2.Pacifying treatment: For those who have irritating pain during the operation, firstly, they can be treated by zinc oxide and other drugs If the damaged part of caries is close to the pulp and cannot be removed at one time, indirect pulp capping is usually carried out first to help promote the remineralization of damaged dentin and repair the dentin before treatment; 4.Root canal treatment: For those who have pulpitis, periapical inflammation or exposed pulp, root canal treatment is often carried out after removing the blackened and decayed part and installing the crown. And install the crown; 5.Extraction: the caries of milk teeth mainly occurs in children, and it can develop into pulpitis and periapical inflammation in a short time. Since the roots of the teeth are blackened and decayed, it is recommended to extract them as soon as possible to avoid the development of inflammation and affect the chewing function and the eruption of the subsequent permanent teeth. Severely damaged non-functional teeth can also be extracted with the advice of the doctor.