Root canal retreatment is a procedure done on a tooth that has previously had a root canal but has not healed correctly. Although root canal treatments are highly successful, there are times when retreatment is necessary. The need for a root canal retreatment can be a sign of many things. It could be due to new infection, decay, the tooth being fractured, or the possibility of a complex anatomy of a tooth that could not be fully treated in the initial procedure. This would not necessarily indicate that the initial root canal failed.