RESUMO
Conventional tomography is a cross sectional imaging modality that provides information about the width of the alveolar bone and the position of the critical anatomical structures such as mandibular canal in the lower jaw. In comparison with conventional CT, it is less expensive, more accessible and patients are exposed to much less radiation. The purpose of this study was to compare the accuracy and validity of spiral computed tomography and spiral conventional tomography. Ten fully or partially edentulous cadaver mandibles were selected. The specific points in anterior, canine, premolar, and molar regions were selected and imagings were performed with both radiographic systems. The distance between alveolar crest to superior border of mandibular canal, as well as mandibular height and width were measured by one oral and maxillofacial radiologist in two successive sessions. The tomography and CT scan [as gold standard] measurements were compared. This evaluation revealed that the absolute mean differences in measuring the vertical dimension in the anterior, canine, premolar, and molar regions were 1.43, 0.74, 0.87, and 0.81 millimeters respectively. The horizontal dimension measurements were 1.21, 0.92, 0.76, and 0.82 millimeters respectively. The absolute mean differences in measuring the vertical and horizontal dimensions were 0.65 and 0.91 millimeters respectively. All these measurements were with in limits of +/- 1 mm error except in the anterior region. Both measurements of vertical and horizontal dimensions had the tendency to be underestimated in anterior region. In measuring the vertical and horizontal dimensions, the validity of spiral conventional tomography were 90.49% and 73.02% respectively, and both were statistically significant [P < 0.001]. From the results of present study it can be concluded that the spiral conventional tomography is an accurate and reliable technique for measuring the vertical and horizontal dimensions in mandible