Comparison of cone-beam computed tomography and osteometric examination in preoperative assessment of the proximity of the mandibular canal to the apices of the teeth.

The risk of postoperative neurosensory impairment after extraction of a third molar will be greater if the inferior alveolar nerve is in close proximity to the apices of the root. Precise preoperative evaluation of the relative positions of the nerve and the mandibular apices is important to protect the nerve from mechanical irritation. The aim of this study was to assess the accuracy of cone-beam computed tomography (CT) in the identification of the positional relations of the mandibular third molar and the inferior alveolar canal using Rood's criteria. Panoramic images of 10 dry hemimandibles were obtained, and 20 teeth each with one of Rood's criteria indicating close relations to the mandibular canal were selected. Cone-beam CT images of the selected points were obtained. The closest distance between the apex of the root and the inferior alveolar canal was measured on cross-sectional cone-beam CT images. The same measurements were made on the corresponding osteometric sections with digital callipers. The intra-class correlation coefficient (ICC) was used to measure the consistency between the two measurements as the reference method, and showed that there was a high level of inter-rater agreement (r>0.90). The mean (SD) deviation of cone-beam CT measurements from the gold standard osteometric measurements was small at 0.30 (0.24). There were almost perfect matches between cone-beam CT and gold standard measurements. Cone-beam CT is an accurate technique to measure the proximity of the mandibular apices to the alveolar nerve.