Acute Apical Periodontitis

Acute apical periodontitis is acute inflammation of the periodontal ligament around the root apex of a tooth, causing pain on biting and tenderness to percussion. The pulp is usually necrotic or irreversibly inflamed, though the condition can also follow trauma or high restoration.

It is the first stage of the apical disease that leads to chronic apical periodontitis, abscess and cyst, and it is among the commonest causes of acute dental pain.

Pathophysiology. Bacteria and their products leave the root canal through the apical foramen and trigger acute inflammation in the apical periodontal ligament, with oedema and a rise in pressure that sensitises nociceptors.

Non-infective causes are occlusal trauma from a high filling or crown, bruxism, overinstrumentation or overfilling during root canal treatment, and orthodontic force.

Moderate to severe localised pain on biting, a feeling that the tooth is elevated or too high, and tenderness to touch and percussion. The pain is often constant, dull and throbbing, and may be worse on lying down.

There may be mild tenderness of the overlying alveolar mucosa but no swelling. A deep carious lesion, large restoration, previous trauma or earlier root treatment is common. Mobility is normal or slight.

Facial swelling, trismus, fever, floor of mouth swelling or difficulty swallowing indicates spreading infection and needs urgent assessment, because the tooth is no longer a simple periapical problem.

• Tenderness to percussion and palpation, with sensitivity testing: cold and electric pulp tests are negative in a necrotic pulp and can be delayed or exaggerated in an irreversibly inflamed pulp.
• Periapical radiograph: normal appearance or slight widening of the periodontal ligament space, with no radiolucency in acute disease. A radiolucency points to chronic apical periodontitis.
• Occlusal assessment with articulating paper to find a high spot.
• Examine for a cracked tooth using transillumination, a bite test and periodontal probing for an isolated narrow deep pocket.
• Check temperature, trismus, swelling and lymph nodes to exclude spread. Blood tests are not needed unless there is systemic illness.

Differential diagnosis.

• Irreversible pulpitis
• Chronic apical periodontitis and acute apical abscess
• Cracked tooth syndrome and vertical root fracture
• Periodontal abscess
• Maxillary sinusitis
• Occlusal trauma and bruxism
• Trigeminal neuralgia and other non-odontogenic orofacial pain

• Definitive treatment of the cause: root canal treatment of a necrotic or irreversibly inflamed pulp, or extraction when the tooth cannot be restored. Opening the canal for drainage and cleaning relieves pain quickly.
• Occlusal adjustment for a high restoration or traumatic contact.
• Analgesia: ibuprofen 400 mg orally every 6 to 8 hours with food (maximum 2400 mg daily, and avoided with active peptic ulcer, renal impairment, anticoagulants or in late pregnancy), with paracetamol 1 g every 6 hours (maximum 4 g daily, 3 g in low weight, liver disease or chronic alcohol use). Combined regular dosing is more effective than either alone for 48 to 72 hours.
• Antibiotics are not indicated for localised acute apical periodontitis without systemic spread. For swelling, fever or spread: amoxicillin 500 mg orally three times daily for 3 to 5 days, with metronidazole 400 mg three times daily added for severe infection, or clarithromycin 500 mg twice daily if penicillin allergic. Reduce amoxicillin to twice daily when eGFR is 10 to 30 and to once daily when under 10.
• Do not leave the tooth in occlusion if percussion pain is severe in a tooth awaiting treatment, and avoid biting on it.

Special groups. Pregnancy: treat with paracetamol and local measures, avoid ibuprofen after 28 weeks, and use penicillin if antibiotics are required. Diabetes and immunosuppression lower the threshold for antibiotics and prompt treatment.

Monitoring. Review after root canal treatment or extraction within 1 to 2 weeks for pain and swelling, and radiographs at 6 and 12 months to confirm periapical healing.

Referral and escalation. Refer to an endodontist for complex anatomy, retreatment or a suspected fracture. Same day maxillofacial referral for facial swelling extending to the floor of mouth or neck, trismus, difficulty swallowing, fever with systemic upset or airway compromise.