Radicular Cyst

Radicular cyst is an inflammatory odontogenic cyst at the apex of a non-vital tooth, lined by epithelium derived from rests of Malassez. It is the commonest cyst of the jaws, making up about 55 to 65% of odontogenic cysts.

It is found mostly in adults between the third and sixth decades, most often in the anterior maxilla. Many cause no symptoms and are discovered on radiographs.

Pathophysiology. Pulp necrosis causes chronic periapical inflammation. Epithelial rests of Malassez proliferate under the influence of cytokines and growth factors and form a cavity lined by stratified epithelium.

The cyst expands by osmotic fluid accumulation, bone resorption and pressure, and lies within a granulation tissue wall. A residual radicular cyst can persist after removal of the tooth.

Usually painless, and often found on radiographs. A slow growing swelling, expansion of the cortex with an egg shell crackle in large cysts, displacement or loosening of neighbouring teeth, and a non-vital tooth.

Acute infection gives pain, swelling, fever and discharge. Large mandibular cysts can weaken the bone and cause a pathological fracture, and a maxillary lesion can extend into the nose or sinus.

• Periapical radiograph or panoramic radiograph: a round or oval, well defined, corticated radiolucency at the apex of a non-vital tooth, typically 5 to 20 mm. Lesions over 10 mm are more likely to be cysts, but radiographs cannot reliably separate cyst from granuloma.
• Cone beam CT for size, relation to the sinus, nasal floor and mandibular canal, and surgical planning.
• Cold and electric pulp tests: negative for the tooth involved.
• Aspiration of straw coloured fluid with cholesterol crystals supports diagnosis, and bloody or purulent fluid indicates other lesions or infection.
• Histology of all tissue removed: non-keratinised stratified squamous epithelium with a thick, inflamed wall, cholesterol clefts, Rushton bodies and foam cells.

Differential diagnosis.

• Periapical granuloma and abscess
• Odontogenic keratocyst
• Periapical cemento osseous dysplasia (vital teeth)
• Lateral periodontal cyst
• Nasopalatine duct cyst (for anterior maxillary lesions)
• Ameloblastoma, central giant cell granuloma and other cystic or tumour like lesions
• Maxillary sinus retention cyst

• Small cysts under about 10 mm: root canal treatment of the non-vital tooth with calcium hydroxide dressing for 1 to 4 weeks, with healing in most cases. Review radiographs at 6 and 12 months.
• Larger, persistent or symptomatic cysts: enucleation and curettage with apicectomy (root end resection of 3 mm and retrograde filling with calcium silicate cement), or extraction with enucleation when the tooth is unrestorable. Send all tissue for histology.
• Large cysts near vital structures (inferior alveolar nerve, sinus, tooth germs): decompression or marsupialisation with a tube or obturator kept for 6 to 12 months and irrigated daily with saline, with later enucleation if a residual cavity remains. This reduces size and spares structures.
• Bone grafting or membrane use for large defects is optional.
• Antibiotics only for acute infection with spread: amoxicillin 500 mg orally three times daily for 5 days (reduce to 500 mg every 12 hours at eGFR 10 to 30), plus metronidazole 400 mg three times daily if severe, or clindamycin 300 mg four times daily in penicillin allergy.
• Analgesia: paracetamol 1 g every 6 hours (maximum 4 g daily) with ibuprofen 400 mg every 8 hours with food.

Monitoring. Radiographs at 6 and 12 months, then annually for 2 to 3 years, to confirm bone fill. Persistent lesions are re-biopsied.

Referral and escalation. Refer to oral and maxillofacial surgery for large lesions, those near vital structures or with uncertain diagnosis. Urgent referral for rapid growth, numbness, pathological fracture or infection with spread.