Root canals are hollow areas in the roots of teeth that contain blood vessels and nerve tissue that give the tooth hot and cold sensation, and the ability to feel pain from an infection. When the pulp becomes infected through decay or as a result of trauma, root canal therapy, which is the act of removing the pulp and canal nerve tissue from a tooth and filling the space with a sealing, inert material will usually make the tooth stop hurting.
This is typically done by opening a hole in the top of the tooth and using a series of files and a disinfecting solution, cleaning, sterilizing and sealing what would otherwise be a source of infection for the tooth. At the end of the root canal treatment appointment, a post and core build-up are often done to avoid having the tooth break before the crown can be done. Following the root canal therapy, it is usually advisable to protect the compromised tooth with a crown, to minimize the possibility that the tooth may crack under function.
A common mistake that patients make is that once they have the root canal therapy done and the pain goes away, they often do not understand that the tooth should get a crown on the tooth. After the time and expense of having root canal therapy on a tooth, it can be disheartening to have the tooth break and have to be extracted because the patient chose to delay getting a crown on a tooth that was treated with a root canal.