A root canal infection occurs when bacteria infiltrate the soft tissue, known as the pulp, inside the tooth’s root canal system. The pulp contains nerves and blood vessels; infection leads to inflammation and tissue death. If the infection extends beyond the tooth’s tip, it causes inflammation in the surrounding bone and ligament, which is medically termed apical periodontitis.
The primary cause of bacterial invasion is deep, untreated tooth decay, which provides a pathway into the pulp chamber. Other common entry points include cracks or fractures. Re-infection of a previously treated tooth can occur if the tooth was not properly sealed, if the final crown or filling leaks, or if complex anatomical variations were undetected.
Recognizing the Signs of Infection
Recognizing symptoms quickly allows for timely treatment and saving the tooth. The most common sign is a persistent or severe toothache that worsens when chewing or applying pressure. This pain is often accompanied by increased sensitivity to hot or cold temperatures, which may linger after the stimulus is removed.
Visible signs include swelling of the gum tissue near the affected tooth, sometimes extending into the face or neck. A specific sign is a fistula, a small, pimple-like bump on the gum that may discharge pus. Dentists confirm the infection through clinical examination, testing the tooth’s response to pressure and temperature, and using X-rays to visualize inflammation or bone loss at the root tip.
Non-Surgical Treatment Options
The initial and most common approach is non-surgical Root Canal Retreatment (Re-RCT). This intervention is necessary when a previous root canal treatment failed to eliminate bacteria or when the tooth becomes reinfected. The goal of retreatment is to access the internal system again to save the natural tooth structure.
The process begins by carefully removing existing filling material and restorative materials, such as a crown or post, to access the root canals. Specialized instruments are used to clean and reshape the entire canal system, eliminating bacteria and infected tissue. This mechanical cleaning is paired with antimicrobial irrigation solutions, such as sodium hypochlorite, to dissolve debris and disinfect microscopic spaces.
Once the canals are cleaned, disinfected, and dried, they are sealed with an inert, biocompatible material, most often gutta-percha. A temporary filling is placed immediately to protect the tooth until a permanent restoration is completed. Oral antibiotics are not the primary treatment for localized infections but may be prescribed if the infection has spread, causing significant facial swelling or systemic symptoms.
Surgical Procedures for Persistent Infection
If non-surgical retreatment is unsuccessful or anatomically impossible, surgical options are necessary to clear the persistent infection. The most frequent endodontic surgery is an apicoectomy, which involves removing the infected tissue and the very tip of the tooth’s root. The procedure is performed through a small incision in the gum to access the bone and the root end.
After the infected root end is removed, a small filling, called a retrograde filling, is placed into the remaining root tip to fully seal the canal system and prevent further bacterial leakage. This procedure is highly targeted and allows the endodontist to treat infections that stem from complex root structures or small accessory canals that were inaccessible during the non-surgical phase. Apicoectomy preserves the tooth when the infection is localized to the root tip area.
Extraction becomes the final option if the infection is extensive, the root is fractured, or if the tooth’s structural integrity is compromised beyond repair. Removing the entire tooth eliminates the source of infection and prevents its spread to the jawbone or surrounding tissues. If extraction is necessary, the tooth should be replaced with a prosthetic option, such as a dental implant or a fixed bridge, to maintain proper bite function and prevent adjacent teeth from shifting.
Long-Term Prevention and Follow-Up Care
Successful treatment depends on follow-up care to prevent recurrence and protect the treated tooth. Following the cleaning and sealing of the canals, a permanent restoration, such as a crown, must be placed without delay. The final crown provides a durable, bacteria-resistant seal and protects the treated tooth structure from fracturing under chewing forces.
Maintaining excellent oral hygiene, including regular brushing and flossing, prevents new decay or gum disease from compromising the tooth’s seal. Regular dental check-ups are necessary so the dentist can monitor the healing of the surrounding bone and tissue. Follow-up X-rays are taken at intervals, such as six months or one year, to ensure the bone infection has fully resolved and the tooth remains healthy.