What is a root canal?

It is a procedure used to save an abscessed tooth by removing the dental pulp (nerve), usually if the tooth is dead or has had the pulp exposed (due to cavities or fractures). After the pulp is removed and any infection has been resolved, the hollow area left behind after the nerve is removed is filled in with a rubber-like material called gutta-percha. Before the days of root canals, most damaged teeth needed to be replaced.

Answer

When a cavity has reached the living part of the tooth, the pulp where the nerve lies, the dentist proceeds to heal the tooth with a root canal in order to avoid a bacterial infection. Once the bacteria have penetrated the pulp, the tooth must be devitalized or have its living tissue removed. The external tooth is still held fast by the root, but in most cases needs to have a cap or splint fitted.