Incidence and risk factors for nerve injuries in mandibular third molar surgery

The inferioralveolar (IAN), lingual (LN) and long buccal nerves (LBN)are the three terminal branches of the trigeminal nerve which are susceptible to injury during surgical extraction of impacted mandibular third molars. While it is not always possible to accurately predict the patients that will be affected with these complications, understanding and identifying the risk factors may allow the adoption of appropriate technique and expertise for specific cases. We embarked on this study to document the incidence and duration of injury to the inferior alveolar nerve (IAN), lingual nerve (LN) and long buccal nerve (LBN) following the operative removal of impacted mandibular third molars and to identify the associated radiographic and operative risk factors.

Pre- and postoperative neurosensory tests were performed for seventy nine patients who had surgical extraction of unilateral impacted mandibular third molars to determine the incidence and duration of complicating nerve injuries. The risk factors for nerve injury were determined among the radiographic variables and documented operative events.

The incidence reported were 6.6% for IAN, 2.6% for LN and 4.0% for LBN; all but one of the nerve injuries resolved within 2 weeks. Depth of impaction (Pell & Gregory Level C) and linguo-version were the significant risk factors for IAN and LN injuries respectively while no risk factors was detected for LBN injury. Some significant operative events were associated with nerve injuries.

Nerve injury in third molar surgery can be predicted based on some radiographic risk factors and some unforeseen intraoperative events. Most of the injuries are transitory in nature.