Coronectomy Sequale: A 5-Year Follow-up Study

The extraction of symptomatic mandibular third molar (M3M) teeth that exhibit radiographic signs of involvement with the inferior alveolar canal (IAN) carries significant risk of morbidity that can be avoided with Coronectomy. This treatment modality allows the surgeon to limit or eliminate the risk of temporary and permanent damage to the IAN.  Few studies have investigated the long-term sequelae of the coronected root. This retrospective observational cohort study was carried out to assess and report on the status of the coronected root following a coronectomy procedure.

All coronectomy procedures were carried out at a single Oral Surgery unit in London, England over a 5-year period with clinical and radiographic follow-up to assess the status of the coronected root in patients who underwent this procedure under local anaesthesia, intravenous sedation and general anaesthesia. Dental panoramic radiographs (DPT) taken prior to the procedure were compared to those taken at subsequent post-operative review appointments to assess the degree and migration pattern of the retained root(s).

Data was collected to include demographic details, degree and angulation of impaction, incidence of infection and dry socket, nerve morbidity, measurements of root migration measured and calibrated on DPT radiographs, and the incidence of subsequent removal of the coronected roots.

150 coronectomies were included in the study of which the male/female ratio was 2:3. The results showed that 61% of retained roots following a coronectomy procedure migrate coronally from their original position and radiographically exhibit the presence of a radiolucent appearance apical to the coronected root.  Of these, 73% were female and 68% were either mesially or vertically impacted. Patients below the age of 30 years exhibited a higher degree of root migration that was statistically significant. The incidence of infection and dry socket was less than 4%. There were no incidences of IAN injury. 5% of the cohort developed postoperative problems requiring subsequent surgical removal of the coronected root(s), which also resulted in no IAN injury.

Root migration is often listed as a complication of coronectomy, however this study has demonstrated that although root migration does occur, it is not associated with any symptoms nor complications in the vast majority of cases. The low rate of subsequent removal of the retained roots was either due to eruption into the mouth or symptoms that persisted beyond the acceptable healing phase, and still did not result in any morbidity to the IAN. Root migration is therefore a sequelae of coronectomy most likely due to disimpaction of the M3M which has erupting potential, but is not a complication unless the retained coronected roots require extraction. Coronectomy is therefore a safe and risk reducing technique for treating M3M which exhibit close proximity to the IAN. 

References:

Long, H., Zhou, Y., Liao, L., Pyakurel, U., Wang, Y., Lai, W. Coronectomy vs. total removal for third molar extraction: a systematic review. J Dent Res. 2012;91:659–664

Leung, Y.Y., Cheung, L.K. Coronectomy of the lower third molar is safe within the first 3 years. J Oral Maxillofac Surg. 2012;70:1515–1522.