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

research _ computed tomography Table 3_Distribution of discrepancies in millimeters observed in each of the 18 sagittal tomographic slices in relation to the axial reference plane used (Pearson’s chi-squared test). Basal plane (n = 18) Occlusal plane (n = 18) n (%) n (%) Discrepancies ≤ 0.5 mm > 0.5 mm 10 (55.56) 1 (5.56) 8 (44.44) 17 (94.44) p-value 0.001 nificant errors would occur, but if the slices were less than 1.5 mm, even if the CT pro- cedure were performed erroneously to some extent, the results would not show much variation and would be more precise. In 2004, Hanazawa et al. compared data obtained by means of a modified CT system and a conventional CT device with real mea- surements taken directly from cadaver man- dibles, finding discrepancies in 90% of the measurements taken with the modified CT system compared with the direct measure- ments and in 87.5% of those taken with the conventional CT device, the discrepancies be- ing approximately 1 mm.25 These radiographic discrepancies can lead to iatrogenic lesions during implant treat- ment, which are of particular concern in pos- terior mandibular regions, where they can produce lesions of the mandibular canal. In this regard, Klinge et al., who studied sensitivity and accuracy in locating the man- dibular canal using cadaverous mandibles, observed that when the accuracy in deter- mining mandibular canal position was evalu- ated, comparing the extent of error with the true value, the error was up to 1 mm in 94% of the CT measurements, but 39% with to- mography, 17% with panoramic radiography and 53% using intra-oral radiography.23 Similar discrepancies between mandibular canal positions determined radiographically using CT and measurements taken directly from the bone have been observed by other authors.15,16,26 Similarly, numerous authors have ob- served small variations between the precision of three-dimensional preoperative imaging and the final surgical positions of the den- tal implants, with variations ranging between 0.7 mm and 1.0 mm,2,27 due to the discrepan- cies between CT measurements and the real _references 1. Ostman PO. Immediate/early loading of dental implants. 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