Endodontics, more commonly known as root canal therapy, is a procedure where the nerves of the tooth are removed. This is often due to the fact that decay has reached far enough into the tooth to start effecting the pulp of the tooth . The nerve, or pulp, of the tooth can become infected, necrotic, or dead and will typically cause pain leading to necessary removal of the nerve. The tooth may be sensitive during treatment and can remain tender for a time after treatment. 

One of the main reasons root canals fail is hard to detect tooth fracture caused either before treatment  or after treatment if a crown is not placed. Teeth with root canals are more brittle than other teeth and a crown is usually necessary to strengthen and preserve the tooth. Root canal therapy is typically done to avoid the extraction of a tooth, however, if a crown is not placed the tooth may fracture and an extraction may be needed.