Accuacy of spiral tomography, panoramic views and parallel periapical radiographic techniques in evaluating the distance between alveolar crest and superior border of mandibular canal

Implants are commonly used in the treatment of fully or partially edentulous patients. Placement of implants requires careful radiographic evaluation of the surgical site so that side effects and neurovascular trauma to the superior wall of the mandibular canal would be avoided. The aim of this study was to assess the accuacy of spiral tomography, panoramic views and parallel periapical radiographic techniques in evaluating the distance between the alveolar crest and the superior border of mandibular canal. Three dried human mandibles were used in this descriptive/analytical study. Three metal pieces were glued to the left side and three to the right side of each mandible. Subsequently, a 5-mm-thick layer of wax was placed on the surface to simulate the soft tissue. Periapical and panoramic radiographs and spiral tomographs were taken from each mandible. Then the mandibles were sectioned and the actual distance between the alveolar crest and the superior border of mandibular canal was measured in each region. Data was analyzed by t-test and repeated measures ANOVA (α = 0.05). The results showed that of the three techniques evaluated only periapical radiographs did not exhibit any significant differences from the actual measurements (p value < 0.05). In addition, there were no significant differences between panoramic and tomographic techniques (p value < 0.05). Based on the results of the present study, parallel periapical technique is recommended for evaluation of implant placement sites and measuring of bone height in the mandible, although tomography can be used to measure bone width.