Nerve injury with third molar removal

Oral Surgery Nerve injury with third molar removal Background.—Among the complications associated with impacted third molar removal are injury to the inferior alveolar nerve (IAN) and the lingual nerve (LN). Although these nerves can be injured during other procedures, the most common cause of damage to these nerves is third molar surgery. The result of such injury includes altered sensation and pain that can limit social interactions and daily functions such as speaking, eating, or drinking. These injuries can have a significant impact on the patient’s quality of life. The incidence of IAN or LN injury associated with third molar surgery was investigated using a Clinical Incident Review (CIR) process. In addition, factors predisposing to permanent neurologic injury were identified. Methods.—The database associated with a CIR process at the Royal Dental Hospital of Melbourne was the source of the information on IAN or LN injury after third molar surgery. The data gathered covered January 2006 to December 2009. The factors assessed included gender, age, operator class, anesthesia method, spatial relationship, depth of impaction, ramus relationship, proximity of the IAN as determined by orthopantomography, cone-beam computed tomography (CBCT) use, and side where the injury occurred. Results.—Surgical removal of mandibular third molars was performed in 10,160 cases, with 81 patients sustaining 84 neurologic injuries. The overall incidence of suffering nerve injury during third molar removal was 0.72%. The incidence of IAN injury during surgical removal was 0.68%, whereas that for LN injury was 0.15%. Temporary injury incidence to the IAN was 0.44%, and to the LN it was 0.069%. Permanent injury incidence was 0.24% and 0.079%, respectively. Symptoms of IAN injury did not resolve in 3 patients (4.3%) and resolved only partially in 21 patients (30.4%). For LN injuries, symptoms remained in 8 patients, of whom 5 (33.3%) had partial resolution and 3 (20%) had no relief. Follow-up extended from 1 month to 2 years, with a mean of 6.7 months. Most nerve injuries resolved completely within a month of injury, but mean complete resolution time was 4.3 months. The range of time for resolution was 2 weeks to 14 months for IAN injuries and 1 to 4 months for LN injuries.

Permanent IAN injury was more likely in patients over age 25 years, when surgery was done by staff dentists, during surgery under general anesthesia, and when mesioangular impactions were involved. The risk of LN was not affected by any factors, although most occurred in patients who had distoangular impaction. General anesthesia was used for 14 of the 15 LN injury cases, and 6 developed permanent tongue numbness. Three patients consulted a neurosurgeon when they experienced no improvement in sensation for 3 months. None of the patients suffering IAN or LN injury developed dysesthesia or pain. Discussion.—Injury to the IAN or LN nerve during third molar surgery can have a significant negative impact on the patient’s function and quality of life. The risk of injury should be minimized as much as possible, which involves careful preoperative clinical and radiographic assessment of the patient.

Clinical Significance.—The risk factors for suffering permanent IAN injury included increasing age, surgery performed by staff dentists, surgery performed under general anesthesia, and teeth with a mesioangular impaction. No risk factors for permanent LN injury were identified. Dentists should be cautious when evaluating patients before third molar surgery, noting if any of the risk factors are present and formulating specific plans to avoid injury to the IAN or LN.

Nguyen E, Grubor D, Chandu A: Risk factors for permanent injury of inferior alveolar and lingual nerves during third molar surgery. J Oral Maxillofac Surg 72:2394-2401, 2014 Reprints available from A Chandu, Melbourne Dental School, The Univ of Melbourne, Melbourne, VIC, Australia; e-mail: chandua@ unimelb.edu.au

Volume 60



Issue 3



2015

e101