When decay reaches the nerve of a tooth, the nerve becomes infected. We call this infection an abscess. One of the ways the dentist treats this infection is to do a “root canal” procedure. This treatment involves removing all of the infection inside the tooth, cleaning out the infected canals, and filling those canals with a medicated filling. Once all of the infected nerves and blood supply have been removed the tooth is now technically “dead” and becomes very brittle. (You can think of a root canal tooth like a dead tree branch that snaps easily when bent.) The canals are then filled and the tooth is sealed off to prevent bacteria from entering the canals. To protect and strengthen a root canal treated tooth, the dentist will rebuild the tooth, and cover it completely with a “cap” or a crown.