Sir, a 39-year-old male was referred to the maxillofacial department by his general dental practitioner (GDP) regarding a persistent extra-oral sinus. The GDP correctly identified an infected lower left second molar (37) and therefore extracted the tooth and prescribed amoxicillin as an adjunct. However to the GDP's surprise, the discharging sinus did not heal and continued to ooze pus for a further three months.

The unsightly appearance of the nodule had become increasingly embarrassing for the patient. His medical history was unremarkable. There was no history of pain, restricted mouth opening or foul taste intra-orally. Follow-up appointments showed uneventful healing of the extraction socket with no sign of intra-oral suppuration.

Extra-oral examination revealed a 1 cm erythematous, smooth nodule present on the left angle of the mandible. Although it was discharging yellow pus, it was not associated with dental pain, paraesthesia, fever or night sweats. The microbiology report from a pus swab showed beta-haemolytic strep sensitive to penicillin.

An OPG not only revealed several carious teeth but also discovered a foreign body of unknown origin present in the anatomical position of the left angle of the mandible (Fig. 1; Fig. 2 shows a 3D reconstruction). Imaging showed severe destruction of alveolar bone from the left angle and ramus of the mandible with close proximity to the inferior dental nerve canal. Although the CT mandible confirmed that the inferior nerve canal was not compromised, it showed a well-defined spicule of dense material measuring approximately 1.2 cm in length. Initial impressions of this spicule were remnants of the extracted tooth along with bony sequestrum. Features of this CT mandible almost certainly represented features of an ongoing chronic infection with the differential diagnoses as follows; retained dental fragment, osteomyelitis and bony sequestrum.

Figure 1
figure 1

OPG revealing the foreign body in the left angle of the mandible

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Figure 2
figure 2

Three-dimensional reconstruction of the foreign body's position

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The sinus tract was removed and the dense spicule retrieved under general anaesthetic. The histopathology from the foreign body showed dead lamella bone with a small amount of slough around its periphery. The bone was of dense lamellar pattern suggestive of an origin from the cortex of the mandible. This concluded that the spicule was bony sequestrum associated with a mandibulo-cutaneous sinus. Dental pathogenesis, osteomyelitis and bony sequestra should therefore be considered as differential diagnoses of extra-oral cutaneous sinus tracts within the head and neck region.1