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CAD/CAM - international magazine of digital dentistry, Italian Edition, No.1, 2017

research _ computed tomography al information is obtained using computed tomography (CT). In edentulous mandibles, the location and course of the mandibular canal remain relatively unchanged in the cranial and caudal borders of the mandible, although some atrophy at the lingual and buccal external borders may occur.5 Recently, some anatomical structures in the jawbone, which are difficult to detect using conven- tional radiography, have been explored using CT.6-9 Investigations of mandibular accessory foramina and canals have drawn attention to anatomical variations of perimandibular neurovascularization.10-13 Although there is a wide range of dental CT equipment marketed as providing exact bone data at a 1:1 scale, several studies have shown discrepancies between radiographic CT measurements and clinical measurements taken directly from the bone.4,14-16 Furthermore, depending on the positioning of the patient when the CT mea- surements are taken, these discrepancies be- tween radiographic measurement and mea- surements taken from real bone can increase even further.17,18 In 2008, Cucchiarelli et al. compared the discrepancies between radio- graphic measurements with CT and mea- surements taken directly from 15 edentulous maxillae, using two different axial reference planes.19 The study showed distortions with regard to the real bone measurements, and these discrepancies were different for each of the two axial reference planes used. The aims of the present ex vivo study were to as- sess the accuracy of dental CT scans and to compare the discrepancies obtained when ei- ther the occlusal plane or the basal plane was used as the axial reference plane. _Materials and methods _Mandibles A total of 39 normal and dry mandibles from adult cadavers aged 35–83 (mean age of 50) were examined following state regu- lations, the study protocol having been ap- proved by the Murcia (Spain) City Hall Health Service. Thirty of these mandibles were eden- tulous and the other nine retained teeth. In order to homogenize the study, multiple ex- odontias were performed on the nine mandi- bles that retained teeth. _Marking the occlusal plane The occlusal plane was marked on the nine mandibles that retained teeth before the exodontias were performed. This was done by marking a line parallel to the teeth from the incisal edge of the central incisor to the ves- tibular cusps of the second molar (Fig. 1a). Once the occlusal plane had been marked, the teeth were extracted. For the 30 edentulous mandibles, the occlusal plane was established Figs. 1a-d_Marking the occlusal plane: (a) marking mandibles with teeth intact before multiple exodontias were performed; (b) marking edentulous mandibles; (c) placing the wax piece to simulate the occlusal plane; (d) wax piece divided into 18 parts with lead strips corresponding to the 18 tomographic slices taken of each mandible). Fig. 1 1_2017 17