Root canal treatment (endodontics) is a necessary procedure when decay has reached the center of the tooth—the pulp—which contains a network of nerve fibers and blood vessels. One of the first symptoms of bacterial penetration into the tooth’s center is pain triggered by hot or cold stimuli that does not subside. Pain during chewing may also occur, and patients often cannot identify which tooth is affected. In some cases, the tooth may be completely painless due to a slowly progressing infection.

Bacteria can then travel through the root canals to the bone, causing inflammation known as a periapical lesion. A periapical lesion may remain dormant for some time, grow without causing symptoms, or produce symptoms so mild that they go unnoticed.

When a periapical lesion begins to grow, it can enter an acute phase marked by swelling and intense pain, or it may manifest quietly as a fistula. In all these situations, the treatment of choice is root canal therapy or tooth extraction. If the periapical lesion continues to grow even after root canal filling, a minor surgical procedure—an apicoectomy—is required to remove the tip of the root along with the lesion.