Localisation of the mandibular canal using conventional spiral tomography: a human cadaver study

For certain surgical procedures (e.g. placement of implants), an accurate localisation of the mandibular canal is of utmost importance to avoid injuries to the neurovascular bundle. The aim of the present study was to evaluate, on human fresh cadavers (n = 6), the accuracy of conventional spiral tomography for the localisation of the mandibular canal. By means of the Cranex TOME multifunctional unit (Orion Corporation Soredex, Helsinki, Finland), tomographic slices were taken at 3 different locations in the left posterior mandible (distal to the mental foramen). The mandibles were then sectioned at these 3 sites with a microtome. With a digital sliding caliper, the following 3 measurements were performed both on the tomograms and the bone sections at the three sites: 1) distance from the crest to mandibular canal, 2) overall bone height and 3) bone width. Overestimations of the distance to the mandibular canal (8/18) ranged from 1.05 to 0.10 mm and underestimations from 0.30 to 1.36 mm. The same number of over- and underestimations occurred for the bone height (1.14 to 0.14 mm and 0.15 to 1.40 mm, respectively). The bone width scored more overestimations (10/18), ranging from 1.40 to 0.12 mm, while underestimations ranged from 0.25 to 1.35 mm. From the present results, it is concluded that spiral tomography using the Cranex TOME multifunctional X-ray unit provides accurate information and sufficient detail for preoperative planning of implant placement in the posterior mandible.