Root canal therapy, also known as endodontic therapy, is a dental treatment to remove an infection from the inside of a tooth. During the procedure, the inflamed pulp is removed, surfaces inside the tooth are cleaned, and a filling is placed to seal the space. Root canal therapy is necessary when oral bacteria invade the pulp inside of the tooth, which can happen if a cavity is left untreated for a long time or a tooth becomes cracked or damaged due to trauma.