4 years after root canal treatment for braces, the tooth is all rotten, it is recommended to remove the braces, and then oral examination and film evaluation, and then decide whether to extract or re-root canal treatment after crown restoration. 4 years after root canal treatment for braces, the tooth is all rotten, may be inside the abutment teeth formed secondary caries, at this time most of the crowns are not close, and the crowns if there is a role in blocking the image, it is recommended that the crowns are removed first, and then filming is carried out. If the crown is mostly decayed or the effect of root canal treatment is not good, it can be extracted directly; if the root tip is not inflamed, the effect of root canal treatment is good, and the residual crown has enough support, it can be considered to remove the decayed tissues and then re-crown restoration or pile crown restoration; if the residual crown is more and the effect of root canal treatment is not good, it can be considered to re-crown restoration after root canal treatment. It is recommended to go to a regular hospital stomatology department to determine the treatment plan after examination by a physician.