Dentigerous Cyst

A dentigerous (follicular) cyst is the second commonest odontogenic cyst, accounting for about 20 percent of jaw cysts, and the commonest developmental cyst. It arises from fluid accumulation between the reduced enamel epithelium and the crown of an unerupted tooth, attached at the cement enamel junction. The mandibular third molar (about 50 percent), maxillary canine, maxillary third molar and mandibular premolar are the most affected teeth. Peak age is 10 to 30 years, with male predominance.

Pathogenesis involves fluid accumulation within the follicle after the crown has formed, due to pressure from an impacted tooth, obstruction of venous outflow and inflammation. Radiographs show a unilocular radiolucency with the crown projecting into the cyst. Dentigerous cysts expand slowly, displace teeth, thin the cortex, and can reach a large size, up to several centimetres.

Complications are pathological fracture, infection, and rarely transformation of the lining into ameloblastoma (about 0.1 to 1 percent) or mucoepidermoid or squamous cell carcinoma. Recurrence after enucleation is low (under 2 percent).

• Usually asymptomatic and found on radiographs when investigating a missing or unerupted tooth.
• Painless swelling of the jaw, facial asymmetry, displacement of teeth, delayed eruption of a permanent tooth.
• Pain, swelling, and fever if infected.
• Large cysts: egg shell crackling on palpation, thinned cortex, pathological fracture.
• Maxillary cyst: sinus involvement, nasal obstruction, and ocular symptoms.
• Red flags: rapid growth, pain, paraesthesia, ulceration, cortical perforation, multilocular appearance, or radiographic root resorption (consider ameloblastoma or other tumour).

• Panoramic radiograph: well defined, unilocular radiolucency around the crown of an unerupted tooth, with a sclerotic border, attached at the cement enamel junction; variants are central (crown surrounded), lateral (crown partly), and circumferential (crown and root).
• Cone beam CT: localisation, relation to the inferior alveolar canal and maxillary sinus, thinning or perforation of cortex; differentiates from tumour.
• Aspiration: straw coloured fluid (cholesterol crystals), protein content above 4 g/dL.
• Histopathology of the whole specimen: thin non-keratinised stratified squamous lining 2 to 4 cells thick, with connective tissue wall containing mucous cells, possible inflammation; excludes keratocyst, ameloblastoma.
• Blood tests are not required; inflammatory markers if infected.
• Exclude odontogenic keratocyst, ameloblastoma (unicystic), enlarged dental follicle (follicular space of under 3 mm), adenomatoid odontogenic tumour, calcifying odontogenic cyst, and radicular cyst.

• Small cysts in children with a developing tooth: marsupialisation or decompression (a window excision with an acrylic drain, irrigated with saline twice daily) to allow eruption of the involved tooth, with orthodontic traction; usually decreasing in size over 3 to 12 months.
• Enucleation with extraction of the associated tooth (when not salvageable) under local or general anaesthesia: complete removal of the cyst lining, with bone curettage; preserve the inferior alveolar nerve.
• Large cysts (over 3 cm) near the inferior alveolar nerve or at risk of fracture: marsupialisation or decompression for 3 to 9 months followed by enucleation.
• Tooth preservation: if the tooth can erupt, use orthodontic extrusion; extraction if impacted in poor position or if lesion is large.
• Mandibular fracture risk: soft diet; fixation if fracture.
• Perioperative: amoxicillin 500 mg orally every 8 hours for 5 days when infected or undergoing extensive surgery, or cefazolin 1 g intravenously once at induction; paracetamol 1 g every 6 hours and ibuprofen 400 mg every 8 hours for analgesia.
• Always send the whole cyst for histology to exclude ameloblastoma, keratocyst, or carcinoma.
• Follow up: clinical and radiographic review at 6 and 12 months, then yearly for 2 to 3 years; bone fill is expected within 6 to 12 months.
• Counselling: the cysts are benign with good prognosis; histological confirmation and follow up are essential.