A root canal is typically done whenever the decay or injury to the tooth invades the inner part of the tooth where the pulp is. This is where the nerve and the blood supply are located. When a root canal is done, the inner portion of the pulp is removed, along with any infection that may have invaded the inside walls of the tooth. Then a sealer material is placed to fill the hole so that new infection can’t get into the tooth. Generally, by removing the nerve and blood supply to the tooth, it can potentially weaken a tooth and therefore, it is common to protect the integrity of the tooth by placing a crown over the tooth.