10 March 2020

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Mandibular Third Molar Extraction: Coronectomy to avoid IAN Injury

Alessandra Abbà

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Surgical extraction of impacted mandibular third molar is a common treatment performed with a therapeutic or prophylactic aim. Complications associated with this practice are various; nonetheless, the most severe side effect is the damage of the Inferior Alveolar Nerve (IAN). In fact it can lead to temporary or permanent paresthesia, hypoesthesia or dysesthesia of the lower lip, teeth, gingiva and skin over the chin affecting the quality of life of the patient.
The most common risk factor is correlated to the proximity of the root to the IAN canal. One of the solution proposed to avoid the risk of this complication, is the coronectomy technique which consist in lefting the root of the teeth in the alveolar socket. 

This study published on Journal of Clinical and Diagnostic Research wants to evaluate the effectiveness of this technique in patients with high risk for inferior alveolar nerve damage.

Matherials&Method:
18 patients between the age of 18 to 40 years and with the characteristic described above, were selected for this prospective clinical study. Twenty impacted third molars were evaluated both clinically and radiographically (no CT scan was taken).
After the subministration of anesthesia and the execution of the flap, the crown was sectioned transversely at the level of the cemento-enamel junction into crown and root and carefully fractured to avoid luxation of the root; the remaining roots were at least 2mm-3mm below the crest of the lingual and buccal side.  For two years patients were evaluated regularly every six months for IAN deficit, lingual nerve deficit, pain, dry socket, infection or other complications.

Results:
The procedure was successfully performed on 18 third molars and two patients had failed coronectomy. All patients completed a minimum of two years follow up. One patient had pain on the soft tissue around the coronectomy site attributed to enamel lipping. One patient had post-operative paresthesia in the lateral border of tongue which resolved after a month. Radiographic evaluation showed coronectomy was adequate in 15 cases, bone formation around the retained roots were observed in 14 cases and root migration was observed in five cases at two year follow-up.
However none of the patients had IAN injury and none required second surgical removal. There was no incidence of post-operative infection and none required second surgical intervention.

Conclusins:
Coronectomy procedure is effective in reducing inferior alveolar nerve injury following third molar surgery, even in high risk cases. In fact it reduces morbidity and has very low incidence of complications. Although numerous studies supporting this theory, the procedure remains controversial due to the risk of infection and other complications arising from the roots left.

(Photocredit: Dr. Giulia Palandrani)

For additional information: Evaluation of Outcome Following Coronectomy for the Management of Mandibular Third Molars in Close Proximity to Inferior Alveolar Nerve.