Periapical Abscess

A periapical abscess is a localised collection of pus at the apex of a tooth root, resulting from infection of necrotic pulp tissue that spreads through the apical foramen into the periapical bone. It follows untreated dental caries, trauma, failed root canal treatment or cracked teeth. Pulp necrosis is the necessary precursor, and the infection is polymicrobial with mainly anaerobes (Fusobacterium, Prevotella, Porphyromonas, Peptostreptococcus) and streptococci.

The condition lies on a spectrum: asymptomatic apical periodontitis with a periapical granuloma or radicular cyst, chronic apical abscess with a draining sinus tract, and acute apical abscess with pain and swelling. Radiographic periapical lesions occur in about 30 to 50 percent of adults with dental infections. The abscess tracks through the cortical plate according to root position and muscle attachments, and can create a sinus on the gingiva or skin. This article addresses the periapical pathology and the endodontic approach to management.

• Acute: severe throbbing spontaneous pain, pain on biting and tooth elevation (feeling that the tooth is too long), swelling of the gingiva or vestibule, tenderness to percussion.
• Tooth non-responsive to cold and electric pulp tests.
• Fluctuant swelling, mobility, and lymphadenopathy; fever and malaise in more advanced infection.
• Chronic: little or no pain, intermittent bad taste, gingival or cutaneous sinus tract with a pus draining opening, which relieves pain.
• Radicular cyst in the long standing lesion, usually asymptomatic.
• Red flags: facial swelling, trismus, difficulty swallowing, floor of mouth swelling, fever over 38.5 degrees C, periorbital oedema or ocular signs (upper tooth), immunosuppression, diabetes.

• Clinical examination: caries or large restoration, discoloured tooth, tenderness to percussion and palpation, sinus tract, mobility, probing depth to exclude periodontal source.
• Pulp sensibility tests (cold spray, electric pulp test): non-responsive in necrotic pulp; compare with adjacent teeth.
• Periapical radiograph: periapical radiolucency (widening of periodontal ligament space in early abscess; well defined radiolucency of 5 to 10 mm or more in chronic disease); cone beam CT for complex cases.
• Gutta percha tracing of sinus tract using a size 25 cone to identify the offending tooth.
• Check temperature, trismus, airway, hydration; blood tests (white cell count, C-reactive protein, glucose) in systemic illness.
• Exclude periodontal abscess, lateral periodontal cyst, cemento osseous dysplasia, maxillary sinusitis, trigeminal neuralgia, and neoplasm.

• Remove the source of infection: root canal treatment (access cavity, working length determination, chemomechanical preparation with sodium hypochlorite 2.5 to 5.25 percent irrigation, calcium hydroxide intracanal dressing for 1 to 2 weeks, then obturation with gutta percha) or extraction if the tooth is not restorable.
• Establish drainage: through the root canal system, by incision of a fluctuant swelling under local anaesthesia (lidocaine 2 percent with adrenaline 1:80 000, up to 4.4 mg/kg), or by extraction.
• Analgesia: ibuprofen 400 mg orally every 8 hours with food with paracetamol 1 g every 6 hours (children: ibuprofen 5 to 10 mg/kg every 8 hours, paracetamol 15 mg/kg every 6 hours); avoid opioids unless severe.
• Antibiotics are not required for localised abscess with drainage. Give antibiotics for systemic involvement, spreading cellulitis, trismus, immunosuppression: amoxicillin 500 mg orally every 8 hours for 5 days (children: 15 mg/kg three times daily; maximum 500 mg), adding metronidazole 400 mg every 8 hours for 5 days for poor response; penicillin allergy: clindamycin 300 mg orally four times daily for 5 days or azithromycin 500 mg once daily for 3 days.
• Failed root canal: retreatment or apicoectomy (root end resection with retrograde filling using calcium silicate cement) when conventional retreatment fails.
• Follow up: clinical review at 24 to 48 hours for drainage, radiograph at 6 to 12 months to confirm healing (lesion shrinkage), and at 4 years for success.
• Prevention: dental caries control, regular dental review, protective sports guards, early treatment of trauma.