Lateral Periodontal Cyst

Lateral periodontal cyst is a developmental odontogenic cyst arising beside the root of a vital tooth, with no inflammatory cause. It is uncommon, making up about 1 to 2% of jaw cysts.

It is found mostly in adults in their fifth to seventh decades, with a strong preference for the mandibular canine and premolar area, followed by the maxillary incisor region. Most are under 1 cm in diameter.

Pathophysiology. The cyst probably arises from rests of the dental lamina (rests of Serres) in the periodontal ligament, or from reduced enamel epithelium, and it grows slowly.

The lining is thin, non-keratinised epithelium with focal thickenings (plaques) of clear, glycogen rich cells. The botryoid odontogenic cyst is a multilocular, grape like variant with a higher recurrence rate.

Almost always asymptomatic and found by chance on radiographs. A few present with a gingival swelling, a bluish swelling of the interdental papilla or mild tenderness. The adjacent teeth remain vital, and are not mobile.

Gingival lesions (gingival cyst of the adult) are seen as a small bluish dome at the gingival margin.

• Periapical or panoramic radiograph: a round or teardrop shaped, well corticated radiolucency, 1 cm or less, lateral to the root and between the roots, with divergent roots in some. The lamina dura of the adjacent tooth is usually intact.
• Cold and electric pulp tests: the adjacent teeth respond normally, which separates the lesion from a lateral radicular cyst.
• Cone beam CT for larger lesions or surgical planning.
• Histology of the excised lesion: thin non-keratinised epithelium of one to a few cell layers with plaque like thickenings of clear cells, and a fibrous wall with little inflammation.
• Biopsy to exclude keratocyst and other lesions with a similar appearance.

Differential diagnosis.

• Lateral radicular cyst from a lateral canal
• Odontogenic keratocyst
• Botryoid odontogenic cyst
• Unicystic ameloblastoma
• Glandular odontogenic cyst
• Periapical cemento osseous dysplasia
• Periodontal abscess and intrabony defect
• Central giant cell granuloma

• Enucleation with conservative curettage, taking care to preserve the vitality and attachment of the adjacent teeth. Recurrence of the unicystic lesion is uncommon.
• Send the specimen for histology to confirm the diagnosis and to exclude odontogenic keratocyst and neoplasm.
• Botryoid or multilocular lesions: more thorough enucleation with peripheral curettage, and long term review, because recurrence reaches about 30% in reports with lower certainty.
• Gingival cysts: local excision with a scalpel under local anaesthesia, with no recurrence in most.
• Antibiotics are not needed for uncomplicated cases. For 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), 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 for 2 to 3 days.

Monitoring. Radiographs at 6 and 12 months, then annually for 3 to 5 years, with a longer period for botryoid lesions. Monitor the vitality of adjacent teeth.

Referral and escalation. Refer to oral and maxillofacial surgery for biopsy and enucleation. Refer urgently if the lesion grows, is multilocular, or histology is not typical.