There may be several causes for the root canal treated tooth becoming painful. For some scenarios, such as fractured root, extraction would be the best option. But for others, such as an infection (e.g. due to an extra canal that may have been missed during treatment), it maybe possible to re-treat the tooth through the crown. Since it's best to keep your natural tooth for as long as possible, you may want to get another evaluation, possibly by an Endodontist (Root canal specialist) who can perform tests/CT scan to determine the cause.
