Painless mandibular expansion around an unerupted third molar

§Case presentation

A young adult referred after a routine OPG taken for orthodontic assessment showed a large pericoronal radiolucency around an unerupted 38.

§Chief complaint

Gradual swelling at the back of the lower jaw noticed 6 months ago

§Medical & dental history

• 01Fit and well, no medication
• 02No allergies, non-smoker
• 0338 never erupted
• 04No pain, occasional food packing distal to 37

§Clinical examination

• 01Smooth bony hard expansion of the left mandibular buccal plate from 37 to the angle
• 02Overlying mucosa normal, no discharge or sinus
• 0338 clinically absent; 37 vital and non-tender
• 04Inferior alveolar nerve sensation intact, no trismus

§ figuresFigures (3)

Verified open-access images only, reproduced for education under their stated licences · no AI-generated or illustrative artwork · Dentigerous Cyst figures pending faculty review.

§Differential diagnosis

§Final diagnosis

Dentigerous cyst associated with impacted 38

A well-corticated unilocular radiolucency attaching at the CEJ of an unerupted tooth, with a pericoronal space greater than 5 mm and no root resorption, is typical. Histology is mandatory because unicystic ameloblastoma and OKC are radiographically indistinguishable.

§Investigations

• 01Pulp sensibility testing of 36 and 37 — both vital
• 02Aspiration — straw-coloured fluid, protein rich, no keratin
• 03Enucleated specimen sent in full for histopathology

§Radiology

• 01OPG — unilocular corticated radiolucency 35 mm attached at the CEJ of 38, crown displaced towards the lower border
• 02IOPA of 37 — intact lamina dura, no root resorption
• 03CBCT — buccal and lingual cortical thinning, inferior alveolar canal displaced inferiorly but cortication preserved

§Treatment plan

• 01Enucleation of the cyst with removal of 38
• 02Preserve 37 — vital and unaffected
• 03Full histopathological examination of the lining

§Surgical procedure

• 01Local anaesthesia with IAN block, buccal envelope flap 36 to retromolar region
• 02Buccal bone removal, tooth sectioned and delivered, lining enucleated intact
• 03Careful protection of the inferior alveolar neurovascular bundle at the cyst floor
• 04Cavity irrigated with saline; primary closure with 3-0 resorbable sutures

§Histopathology report

Cyst lined by thin, non-keratinised stratified squamous epithelium 2-4 cells thick, without rete ridges, on a loose fibromyxoid connective tissue wall containing odontogenic epithelial rests. No dysplasia, no ameloblastic change. Dentigerous cyst.

§Follow-up & outcome

• 011 week — uneventful healing, no paraesthesia
• 026 months — radiographic bone infill, socket consolidating
• 0324 months — near-complete ossification, no recurrence

Outcome: Complete bony healing with preserved inferior alveolar nerve function and no recurrence at 2 years.

§Discussion

• 01Dentigerous cysts are the second most common odontogenic cyst and most often involve mandibular third molars and maxillary canines.
• 02Large lesions in children can be treated by marsupialisation to allow the tooth to erupt and to protect adjacent structures.
• 03Mural ameloblastoma or mucoepidermoid carcinoma arising in the lining is rare but is the reason every specimen is examined histologically.

§Clinical pearls / learning points

• 01A pericoronal radiolucency over 5 mm around an impacted tooth is a cyst until histology says otherwise.
• 02Preserve the inferior alveolar nerve — dissect the cyst floor under direct vision.
• 03Marsupialisation is the conservative option when the associated tooth can still erupt.

§Viva questions

§MCQs

§Related diseases

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