Impacted lower third molar extraction: Lingual position of IAN near LTM ups risk of neurosensory deficits, study finds

The researchers reveal an increased risk of neurosensory deficits when the inferior alveolar nerve (IAN) is directly positioned lingually to the tooth roots, and the use of cone-beam CT improves the risk assessment and comprehensive presurgical anatomic information.

"The overall incidence rate of acute neurosensory deficits of the mandibular nerve within the first seven days after the extraction of an LTM was 5.9%, with IAN impairment constituting 48.5% of cases and lingual nerve deficits constituting 36.4%," the researchers reported.

The incidence rate of persisting deficits of the mandibular nerve was 1.3% of the removed teeth, impacting the IAN and lingual nerve in 0.8% and 0.5% of cases, respectively.

Neurosensory deficits are one of the leading complications that occur after impacted lower third molar extraction resulting in an impaired patient's quality of life. Marcus Rieder, Medical University of Graz, Graz, Austria, and colleagues aimed to evaluate the incidence of neurosensory deficits after lower third molar extraction and compare it radiologically to the corresponding position of the inferior alveolar nerve.

For this purpose, the researchers compiled all patients who underwent impacted lower third molar extraction between January and December 2019 in a retrospective study. Therefore, they assessed clinical data as well as preoperative radiological imaging.

The study led to the following findings:

• The study included 418 patients who underwent lower third molar extractions (n = 555). Of these, 5.9% had short-term (i.e., within the initial seven postoperative days) and 1.3% long-term (i.e., persisting after 12 months) neurosensory deficits documented.
• The inferior alveolar nerve position concerning the tooth roots showed apical position in 27%, buccal position in 30.8%, lingual position in 35.4%, and inter radicular position in 6.9%

The occurrence of neurosensory deficits at the mandibular nerve after lower third molar surgery is relatively rare.

According to the authors, their results are consistent with the majority of published studies found. "A lingual position of the IAN close to the LTM significantly increases the risk of nerve deficits. In this context, cone beam computed tomography scan use appears promising as it can improve risk assessment and provide comprehensive preoperative patient information," the researchers wrote.

"It is noteworthy that in our study, no decreased quality of life was observed in patients with persistent nerve deficits," they concluded.

Reference:

Rieder, M., Remschmidt, B., Schrempf, V., Schwaiger, M., Jakse, N., & Kirnbauer, B. (2022). Neurosensory Deficits of the Mandibular Nerve Following Extraction of Impacted Lower Third Molars—A Retrospective Study. Journal of Clinical Medicine, 12(24), 7661. https://doi.org/10.3390/jcm12247661