Evaluation of the relationship between mandibular third molar and mandibular canal by different algorithms of cone-beam computed tomography

Introduction: Knowledge of the exact location of the inferior alveolar nerve (IAN) bundle is a very important factor for safe and quick removal of bone. The aim of this study was to evaluate the relationship between the mandibular third molar and the mandibular canal by different algorithms of cone-beam computed tomography (CBCT).Materials and Methods: In this cross-sectional study 94 mandibular CBCT images taken with CSANEX 3D machine (Soredex, Finland), in which there was close proximity between the wisdom teeth and the inferior alveolar nerve, were selected using convenience sampling technique. Vertical and horizontal relationships between the mandibular canals and the third molars were depicted by three different image processing algorithms of Nerve option, Panorama and Cross-sectional. Data were analyzed with SPSS 20 by calculating kappa ratio and by using  chi-squared test (α=0.05). Results: There were significant differences (p value < 0.05) in the vertical and horizontal relationships between the three different image processing algorithms. Kappa ratio for comparison of the vertical distance between the Nerve option view and Cross-sectional view was 0.713 (p value < 0.001). Kappa ratio for comparison of the vertical distance between the Panoramic view and Cross-sectional view was 0.696 (p value < 0.001). Kappa ratio for comparison of the horizontal distance between the Nerve option view and Cross-sectional view was 0.283 (p value < 0.001). Kappa ratio for comparison of the horizontal distance between the Panoramic view and Cross-sectional view was 0.197 (p value = 0.001).Conclusion: The results of this study showed differences in the position of the inferior alveolar nerve with different views of CBCT. Therefore, to determine the exact relationship between the nerve and tooth the use of only one view is not enough and it  is better to use different views of CBCT for better diagnosis. Key Words: Cone-beam computed tomography, Mandibular nerve, Mandibular third molar