Lateral Periodontal Cyst Aspiration — ORE Part 1 MCQ

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ModerateOral PathologyLateral Periodontal Cyst AspirationORE Part 1

A 30-year-old patient presents with a well-defined unilocular radiolucency between the roots of the lower left canine and first premolar. Both teeth are vital. The radiolucency is approximately 6 mm in diameter with a thin corticated border. Aspiration yields a thin straw-coloured fluid. What is the most likely diagnosis?

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Correct answer: B — Lateral periodontal cyst

Explanation lettering: E = shown as A · A = shown as B · D = shown as C · C = shown as D · B = shown as E

Lateral periodontal cyst (LPC) is the correct diagnosis. The clinical and radiographic presentation is pathognomonic: a well-defined, unilocular radiolucency in the inter-radicular region of the mandibular canine–premolar zone, measuring <1 cm, with intact cortication, asymptomatic presentation, and associated with vital teeth. The straw-coloured fluid on aspiration is consistent with LPC cystic fluid. Radicular cyst (B) and periapical granuloma (C) are inflammatory lesions requiring non-vital teeth with endodontic pathology—excluded here. Traumatic bone cyst (D) is typically painless but yields minimal or blood-tinged fluid and lacks the well-corticated border. Odontogenic keratocyst (E), although unilocular in some cases, arises from odontogenic epithelium in different locations (often posterior mandible), presents with yellowish or keratinous aspirate, and is not classically inter-radicular in vital teeth. LPC is a developmental, non-inflammatory cyst that represents 0.4–0.7% of odontogenic cysts and is distinguished by its vital-tooth association.

Reference: The lateral periodontal cyst: aetiology, clinical significance and diagnosis. PubMed 11202873. https://pubmed.ncbi.nlm.nih.gov/11202873/ (2001); Guided Bone Regeneration in the Treatment of Lateral Periodontal Cysts. PMC 12152507. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12152507/ (2024).