Efficacy of Computed Tomography Based Evaluation for Risk of Inferior Alveolar Nerve Damage

Abstract

Purpose : The aims of this study were to evaluate the incidence of inferior alveolar nerve (IAN) injury and various risk factors of IAN damage, and to assess the efficacy of CT on the evaluation for risk factors of IAN damage after lower third molar removal.

Patients and Methods : This study included total 735 patients who underwent surgical procedures for the 3rd molar extraction between January 2000 and August 2009 and total number of teeth was 1058 lower third molars. Among them, 271 teeth were additionally examined by dental computed tomography (CT). The prediction variables for IAN damage such as age, Pederson difficulty index, radiographic risk signs through panoramic view or CT scan were evaluated statistically, and sensitivity, specificity, positive predictive value, and negative predictive value were calculated about each radiographic risk sign.

Results: Total 5 cases (0.5%) out of 1058 lower third molar extraction cases showed symptoms of IAN damage after surgical procedures. Patient age, darkening of root on panoramic radiograph, and contact or intrusion of root into IAN on CT scan may be related with IAN damage after extraction, but the incidence of IAN damage is too low to verify statistical significance. Pederson difficulty index seems not reliable prediction factors for risk evaluation of IAN injury. The presence of risk sign(s) on CT scan had positive predictive value of 0.4%, and absence of these had a negative predictive value (99.3%).

Conclusion: The incidence of persistent (over 6 months) and temporary (less than 6 months) IAN damage is 0.2%, 0.3% respectively. Although usefulness of CT scan as a positive predictor is limited due to very low incidence of IAN damage, preoperative CT scan seems to be an efficient approach of negative prediction for risks of IAN damage during lower third molar extraction.