Assessment of the proximity between the mandibular third molar and inferior alveolar canal using preoperative 3D-CT to prevent inferior alveolar nerve damage
OBJECTIVE The purpose of this study was to locate the mandibular canal in relation to the impacted mandibular third molar by conventional cross-sectional tomography. METHOD AND MATERIALS Conventional axially corrected cross-sectional tomograms of 347 successive impacted mandibular third molars of 234 patients referred for removal of the impacted teeth were acquired with a Scanora x-ray unit. The images were assessed for location of the mandibular canal and the impacted mandibular third molar. Descriptive analysis was performed. RESULTS Examination of the tomograms revealed the alveolar nerve to have, in relation to the mandibular third molar, a lateral (buccal) course in 53.6% (n = 186), a course between the roots in 26.8% (n = 93), a lingual course in 13.0% (n = 45), and an inferior course in 6.0% (n = 21). Supplementary canals were found in 6.3% (n = 22). Two of the tomograms (0.6%) could not be evaluated, in 1 case because of incorrect patient positioning, resulting in an incorrectly adjusted transverse cut, and in the other case because of a mandibular carcinoma. CONCLUSION Conventional axially corrected cross-sectional tomograms offer additional information in cases where there is a close relationship between impacted third molars and the alveolar nerve (superimposition of the roots and the canal, grooving, or a varied direction of the canal on the panoramic radiograph) and may contribute to a higher level of intrasurgical safety.