If the only remaining root is in the gum, surgical extraction is required in most cases. If the damage is in a flush gingival or subgingival position of 1-2mm and the root length is sufficient, the tooth may still have some retention value. The shape and function of the affected tooth can be restored by root canal treatment, crown lengthening, and pile core crown restoration. For residual roots that have no retention significance, extraction of the root is required under local anesthesia. To determine whether the root remnant can continue to be used, firstly, the root exists and most of the crown is missing, there is no way to apply general crown restorations; secondly, the root must be of sufficient length, as seen by x-ray of the subgingival root and length, and the crown to root ratio after crown restoration should be at least 1:1 ratio; in addition, the periodontal tissue should be healthy, after perfect root canal treatment, and there can be sufficient clearance when the upper and lower jaws bite together, one tooth plus pile crown gap. If the above conditions are met, the residual root can be utilized.