After crowning, root canal treatment is not recommended for this tooth, although this is not absolutely the case. Clinically, if a metal crown is worn and it is determined that there is no problem with the tooth itself, but only a certain amount of inflammation at the root tip, then it is indeed possible to consider further pulpotomy on the crown, after which extraction, root canal expansion and root canal treatment can be performed on the tooth. However, it is relatively less common, especially for porcelain crowns, if the pulp is opened on the crown, it is likely that the crown will be destroyed in the process of pulp opening, so for teeth that have been crowned, once the problem occurs, in most cases it is necessary to remove the crown and then perform root canal treatment.