Unusually sited lower third molar

Background

An ectopically positioned third lower molar is a rare occurrence,1 with maxillofacial surgeons more commonly dealing with impacted lower third molars.2 The aetiology is unclear, but theories postulated to explain the displacement of third molars include aberrant eruption, trauma and ectopic formation of tooth germ.3 While some are discovered as an incidental finding after routine examination, it is often pain swelling and trismus that cause the patient to seek medical care.1 Eighty per cent of facial abscesses are related to dentoalveolar pathology and should be considered as the most likely cause.

Case presentation

A 60-year-old female patient was admitted under our care on New Year’s Eve following a stay of several days with our ENT colleagues at a satellite hospital for treatment of suspected parotitis. She presented with significant facial swelling (figure 1), pain, left lower lip paresthesia and trismus limited to around 1 cm mouth opening. Ultrasound scan showed a normal parotid gland but an abnormal collection and area of infection arising from the mandible. A CT scan and OPG radiograph revealed an ectopic tooth placed high up in the posterior ramus/condyle. There was no clear evidence of an associated cyst or other pathology, but there was significant erosion of the cortical bone perforating through to the buccal aspect (figure 2). The patient was clinically stable but remained an inpatient for 3 days receiving intravenous antibiotics and steroids to treat the acute infection and inflammatory response. The swelling reduced and her trismus subsided.

Ectopic third molars without pathology or symptoms can usually be left in situ,2 but in this case, the tooth was found to be the source of the pain, swelling and trismus, and the patient was worked up for an elective operation. An extended wisdom tooth incision to the coronoid process allowed subperiosteal dissection either side of the ramus to the posterior border with lingual nerve protection used throughout using lower border retractor (figure 3). This also reduced the chance of medial displacement of the tooth. Fortunately, the inferior alveolar nerve had been pushed to the posterior border of the ramus, so the lingual bone could be burred to improve access and the tooth was removed lingually without sectioning using a curved Warwick James to mobilise through the buccal defect. The ramus was well curetted during surgery both lingually and buccally under direct vision and no samples for histopathology were found. It is possible that some lining may have remained lingually close to the nerve, but nothing convincing that was safe to remove was seen or sampled. Although this was not directly observed, a communication into the mouth from the lingual aspect of the mandible most likely led to the infection of the ectopic tooth as there was no evidence of cystic change. The other differentials would be a dentigerous cyst, or from a haematogenous origin. During the operation, we also removed the lower right molar teeth, which had periapical pathology.

Clinical management of ectopic third molars must always take into account patient symptoms, surgical risk, pathology and patients wishes.1 2 4 This case demonstrates a good approach for removing an ectopic third molar from the mandibular posterior ramus/condyle while avoiding morbidity.

Outcome and follow-up

The patient recovered fully postoperatively, and the sensory disturbance to her lower left lip completely resolved a couple of weeks after the operation. At 6-month follow-up, she has no presenting complaints. There are also signs of bony infill on subsequent radiographic imaging. (figure 4).