Does the extent of cortical perforation of the inferior alveolar nerve canal by the roots of third molar teeth seen on cone beam computed tomography predict postoperative paraesthesia? - A prospective clinical study

The aim of this study was to assess the extent of cortical perforation in millimetres (mm) in inferior alveolar nerve (IAN) canal on coronal section of cone beam computed tomography (CBCT) to predict IAN injury in high risk patients. We also analysed relation of position of canal and number of roots with likelihood injury to IAN. We conducted a prospective clinical study of 100 high risk patients in which 78 patients had cortical perforation which was verified by CBCT. 13/78 of 3rd molars were associated with IAN injury at 1 month post extraction. Out of those, only 3 had a permanent decrease in sensation and remaining 10 had temporary paraesthesia. Owing to the large number of patients with cortical defects, we further sub-categorised them into five groups based on cortical perforation: Type 1 – No involvement, Type 2–1 - 3 mm, Type 3–4 - 6 mm, Type 4–7 - 9 mm, Type 5 – more than 9 mm. All of the 8 patients who had more than 6 mm (Type 4 and Type 5) had some sensory disturbance whereas no IAN injury was found in patients of type 1 and type 2. There were 5/23 who had nerve injury in type 3. The association between cortical perforation and IAN injury was statistically significant (p - <0.0001). Extent of cortical perforation can be a reliable predictor to predicate IAN injury prior to lower third molar extraction. In addition, the presence of abnormal sensation was significantly associated with different canal positions (p -