Chronic Apical Periodontitis

Chronic apical periodontitis is long standing inflammation and bone resorption around the root apex of a tooth, driven by infection of the root canal system. It is usually painless or mildly symptomatic and is found on a radiograph as a periapical radiolucency.

It is the commonest result of untreated pulp necrosis and of failed root canal treatment. A sinus tract draining to the gingiva or skin marks the chronic suppurative form.

Pathophysiology. Bacteria and their products persist in the canal and apical region. The host response, with T and B cells, macrophages and osteoclasts, resorbs the lamina dura and cancellous bone around the apex, forming a granulomatous lesion.

Persistent or secondary infection, an extraradicular biofilm, a cyst, a missed canal or a coronal leak explains failure after treatment.

Often asymptomatic and discovered on routine radiographs. Some report mild tenderness to biting, a discoloured crown, a bad taste, or a recurrent gum boil. The tooth may be tender to percussion and palpation, with normal or slightly increased mobility.

A sinus tract opens on the attached gingiva or alveolar mucosa, and a cutaneous sinus on the chin or cheek can be misread as a skin lesion. Acute flare up produces pain and swelling, and spreading swelling, fever or trismus needs urgent assessment.

• Sensitivity testing: cold and electric pulp tests are negative in a necrotic pulp. Test neighbouring teeth for comparison.
• Periapical radiograph shows a well defined or diffuse periapical radiolucency with loss of the lamina dura. A lesion under 2 mm may not be visible.
• Cone beam CT for suspected missed canals, root fracture, large lesions, or planning of surgery. It is more sensitive than plain films for periapical bone loss.
• Trace a sinus tract with a gutta percha point and a radiograph to find the source tooth.
• Periodontal probing to exclude a narrow isolated pocket from a vertical root fracture or endo perio lesion.
• Biopsy of a persistent lesion after treatment, to exclude cyst, tumour or other disease.

Differential diagnosis.

• Periapical granuloma and radicular cyst (cannot be told apart on radiographs alone)
• Acute apical abscess in flare up
• Periapical cemento osseous dysplasia (vital pulp)
• Osteomyelitis of the jaw
• Langerhans cell histiocytosis and other bone lesions
• Odontogenic keratocyst and central giant cell granuloma
• Metastasis and lymphoma of the jaw
• Normal anatomy such as the mental foramen or incisive canal

• Orthograde root canal treatment: access, working length, shaping with irrigation using sodium hypochlorite 1 to 5.25% (usually 2.5%) with 17% EDTA for smear layer removal, intracanal calcium hydroxide dressing for 1 to 4 weeks, and a sealed root filling with a coronal seal. Primary treatment heals in roughly 85 to 90%, and retreatment in roughly 70 to 80%, with lower success when a large lesion or a missed canal is present.
• Retreatment of a failed root filling, or apical surgery (root end resection about 3 mm with retrograde filling using a calcium silicate cement) when retreatment is not possible or has failed.
• Extraction when the tooth cannot be restored, is fractured vertically or the patient declines root treatment, with curettage of granulation tissue.
• Antibiotics have no role for the chronic lesion. For acute exacerbation with swelling or systemic upset: amoxicillin 500 mg orally three times daily for 5 days, adding metronidazole 400 mg three times daily when infection is severe, or clindamycin 300 mg four times daily in penicillin allergy. Reduce amoxicillin to 500 mg every 12 hours when eGFR is 10 to 30.
• Analgesia: ibuprofen 400 mg every 8 hours with food and paracetamol 1 g every 6 hours (maximum 4 g daily, 3 g in low weight or liver disease), for a short course.
• Anticoagulated patients and those with bleeding disorders need the INR or factor status checked before surgery, and local haemostatic measures.

Special groups. Diabetes, immunosuppression and bisphosphonate or denosumab treatment make healing slower and raise the risk of osteonecrosis after extraction, so root canal treatment is preferred where the tooth is restorable.

Monitoring. Clinical and radiographic review at 6 and 12 months, then annually for up to 4 years. Healing means a shrinking radiolucency and absence of symptoms. Failure at 12 months with an enlarging lesion needs retreatment, surgery or extraction.

Referral and escalation. Refer to an endodontist for retreatment, calcified canals or surgery, and to oral and maxillofacial surgery for large lesions, suspected cyst or tumour, or extraction in a patient at high risk of osteonecrosis. Urgent referral for spreading swelling, trismus or fever.