Age and Risk of Inferior Alveolar Nerve Injury After Removal of Lower Third Molars Close to the Mandibular Nerve

Extraction of lower third molars (3 Ms) carries a risk of inferior alveolar nerve (IAN) injury. Anatomical proximity is a well-known risk factor, although the effect of patient age remains insufficiently explored.

The study purpose was to measure the association between age and IAN injury among patients whose 3 Ms are close to the mandibular canal.

This case-control study included patients at increased risk for IAN injury due to close proximity of the lower 3 Ms to the mandibular canal, as assessed by preoperative cone-beam computed tomography. The exclusion criteria were poor preoperative CBCT, cysts or tumours related to the 3 Ms, intake of drugs related to osteonecrosis of the jaws, and previous radiotherapy.

The exposure variable was age.

The outcome variable was IAN neurosensory status. Cases were defined as IAN neurosensory deficit at 1 month after extraction.

The following covariates were analyzed: sex, body mass index, operated side, 3 Ms position (Pell and Gregory and Winter classifications), number and shape of the roots, IAN position (lingual, buccal, or apical), ostectomy, and tooth sectioning.

Univariate associations were explored with simple binary logistic regression, reporting crude odds ratios (ORS). The adjusted OR for age was calculated using multivariate binary logistic regression using Stata 14.2. Statistical significance was set at P < .05.

A total of 219 patients (60% female) were screened; the mean age was 28.2 ± 10.7 years. Thirty-seven subjects (16.89%) presented an IAN neurosensory deficit 1 month postextraction (cases). These cases were compared with 111 randomly selected subjects without IAN impairment from the initial cohort of 219 patients. The risk of IAN neurosensory deficit increased with age (adjusted OR per year = 1.06; 95% CI, 1.01 to 1.11; P = .008). Impaction depth (OR = 9.29; 95% CI, 2.44 to 35.39; P = .001) and lingual position of the IAN (OR = 3.09; 95% CI, 1.06 to 9.03; P = .039) were also associated with increased risk. Each additional year of age increased the adjusted OR of neurosensory deficit by 6%.

IAN neurosensory deficit occurred in 16.89% of subjects. Age was a statistically significant independent risk factor of IAN injury and should be considered in preoperative planning.