Tooth rotten only the root is called stump, if the stump has no obvious lesions, can be retained without extraction, if the stump has lesions, the treatment effect is not good should be extracted, specific as follows. 1. Residual root without obvious lesions: the residual root can be retained after perfect root canal treatment, and the periapical tissue without obvious lesions. Pile core crown repair or overdenture repair can restore the shape and function of the crown of the affected tooth. Preservation of the residual root is beneficial in maintaining the alveolar bone height and preserving the periodontal proprioceptors. If the root meets the criteria for a crown, it can be restored. 2. Disease in the residual root: If there is inflammation in the residual root or periapical tissues, and the effect of treatment is not good, it should be extracted as soon as possible to avoid the formation of a chronic lesion, which may cause local infection. It is recommended to go to the hospital, with the help of the doctor for targeted treatment.