A root canal treatment (RCT) is a common dental procedure designed to save a tooth whose soft inner tissue, or pulp, has become infected or inflamed due to deep decay or injury. The treatment involves removing the diseased pulp, cleaning and disinfecting the inner chambers, and then sealing the space to prevent bacteria from re-entering. While RCT has a high success rate, the possibility of the tooth failing to heal or becoming reinfected remains a concern. Failure means bacteria have returned or were never fully eliminated, leading to the recurrence of symptoms and a threat to oral and general health.
Recognizing Signs of Reinfection
The most common indicator that a root canal has failed is the return of discomfort or the persistence of pain long after the initial healing period. Patients often report a dull ache or sensitivity, especially when biting down or applying pressure to the affected tooth. This recurring pain signals that the infection has likely re-established itself within the root canal system or the surrounding bone tissue.
Another visible sign of reinfection is localized swelling or tenderness in the gum tissue near the treated tooth. Sometimes, a small, pimple-like bump, known as a fistula or gum boil, may appear on the gum line, which can drain pus and result in a foul taste or odor. The tooth itself may also begin to darken or change color, indicating internal damage or lingering bacterial activity.
Root canal failure happens for a few primary reasons related to the original procedure or subsequent restoration. The complex anatomy of a tooth can include very narrow, curved, or extra root canals that may have been missed or incompletely cleaned during the first treatment, leaving bacteria behind. A crack or fracture in the tooth or a faulty crown or filling can also allow new decay and bacteria to leak back into the sealed root canal system, causing reinfection.
Risks of Leaving an Infection Untreated
Ignoring the signs of a failed root canal allows the bacterial infection to progress, leading to localized destruction. The most immediate consequence is the formation or enlargement of a periapical abscess, a pocket of pus that collects at the tip of the tooth root. This collection of pus creates pressure and can erode the surrounding jawbone tissue, causing bone loss that compromises the tooth’s stability.
The infection is not always contained to the area immediately around the tooth root. If the abscess bursts, the infection can spread into the soft tissues of the face and neck, potentially causing cellulitis. Cellulitis is a rapidly spreading bacterial skin infection that can cause swelling and may compromise the airway, requiring immediate medical intervention.
In less frequent cases, bacteria from the dental infection can enter the bloodstream, traveling to other parts of the body. This can lead to systemic complications, such as infections in other organs or sepsis. Sepsis is a response to infection that can cause organ failure, emphasizing that an untreated dental infection is a medical risk.
Treatment Options for a Failed Root Canal
When a root canal is confirmed to have failed, the first and most common course of action is non-surgical retreatment. This procedure is similar to the initial root canal but involves reopening the tooth, removing the existing filling material, and using specialized instruments to thoroughly clean and disinfect the entire canal system. The endodontist searches for missed or accessory canals and then re-seals the tooth with fresh material, aiming to eliminate the persistent bacteria.
If non-surgical retreatment is not feasible due to a complex obstruction or if the infection persists, a surgical procedure known as an apicoectomy may be recommended. This microsurgical approach involves accessing the infection directly through the gum tissue, bypassing the crown of the tooth. The endodontist removes the infected tissue, trims the tip of the tooth root (the apex), and places a small filling to seal the root end, promoting bone healing.
The final option, considered when the tooth structure is compromised by fracture or extensive bone loss, is extraction. Removing the tooth is necessary to eliminate the source of infection and prevent further damage to the jawbone. Following extraction, the space should be replaced to maintain proper bite function and prevent adjacent teeth from shifting. Replacement options include a dental implant, which serves as a new artificial tooth root, or a fixed dental bridge.