Risk stratification against inferior alveolar nerve injury after lower third molar extraction by scoring on cone-beam computed tomography image.

The study aimed to stratify the risk of inferior alveolar nerve injury (IANI) after lower third molar (LM3) surgery with a scoring system using identified predictive factors based on cone-beam computed tomography (CBCT) images. In a case-control study, the primary outcome was IANI occurrence. The control group included randomly selected patients without IANI. Predictor variables included patient demographics, surgical situations, Pell-Gregory classification, and inferior alveolar canal (IAC)-associated factors on CBCT. Study variables were analyzed using logistic regression models. Risk stratification was assessed by a scoring system that was constructed using independent predictors. The 858 patients who underwent LM3 surgery (1177 teeth) after CBCT scan were divided into case (25 patients, 2.9%, 27 teeth) and control (235 patients, 300 teeth) groups. In the multivariate model, lingual/inter-radicular position of IAC [odds ratio (OR) 7.21; P < 0.001; assigned score, 2], multiple roots closed to the IAC with cortical perforation (OR 3.72; P = 0.015; 1), and age > 30 years (OR 4.99; P = 0.008; 2) were associated with an increased IANI-risk. The IANI-risk scoring system could be stratified into low- and high-risk groups at a cutoff score of 3 (sensitivity, 68.0%; specificity, 90.6%; positive predictive value, 17.8%; positive likelihood ratio, 7.23). In conclusion, the high-risk group of IANI after LM3 surgery corresponded to individuals with multiple factors: lingual/inter-radicular IAC position to LM3, multiple roots with perforated IAC, and increased age (> 30 years). Raising awareness of the higher probability for IANI is needed for patients with multiple aforementioned factors.