The Usefulness of Panoramic Radiography using a Lead Ruler for Dental Implant Planning

PURPOSE: If damage to the neurovascular bundle of the mandibular canal during dental implant surgery of the mandible is to be prevented, accurate measurement of the distance between the alveolar crest and the mandibular canal, as seen on panoramic radiographs, is important. The purpose of this study was to compare the accuracy of panoramic radiography using a lead ruler with that of computed tomography for the measurement of the distance between the alveolar crest and superior border of the mandibular canal and to evaluate the usefulness of panoramic radiography using a lead ruler. MATERIALS AND METHODS: For control study, panoramic radiography of the dry mandible was undertaken using a lead ruler, and computed tomography was added. The distances between the alveolar crest and the superior border of the mandibular canal and between the alveolar crest and the lowest border of the body of the mandible were measured at the level of the 2nd premolar to the 3rd molar. These measurements were compared with actual measurements of the dry mandible in the same areas. The cases of 87 patients[49 men, 38 women; age range, 20 -84 (mean, 42) years] who had undergone panoramic radiography using a lead ruler were reviewed. They were catergorized according to sex, the presence of teeth, and whether under or over 50 years of age. All measurements were compared and analyzed using the Student t-test. RESULTS: Measured values obtained from a panoramic radiograph using a lead ruler(magnification:100.32%+/-5.92) and from a computed tomograph(magnification:100.22%+/-5.55) deviated less from actual measurements on the dry mandible (p > 0.05). The distance from the 2nd premolar to the 3rd molar was greater in male adults (19.62 mm +/-3.95) than in female (17.54 mm +/-4.04) (p 0.05), except 2nd pre molar and 1st molar in the female. CONCLUSION: Panoramic radiography using a lead ruler is a simple and accurate modality for the presurgical planning of dental implant surgery. It is suggested that the successful long-term rate of dental implantation may be higher in dentulous male than in edentulous female molars.

Quantitative Morphologic Assessment of Thoracolumbar Vertebrae in Korean Women by Morphometric X-rayAbsorptiometry

PURPOSE: To compare the accuracy of lateral radiography of the spine with that of morphometric X-rayabsorptiometry(MXA) in vertebral morphometry, and to evaluate normal vertebral morphometry using MXA in Koreanwomen. MATERIALS AND METHODS: A spine phantom was constructed using copper pipe. Its anterior and posteriorheights were measured directly, with lateral radiographs and with MXA, and the values thus obtained were compared.Inter -and intra -observer variations were evaluated by three radiologists. The vertebral morphometry of 30 youngwomen volunteers were imaged using thoracic and lumbar lateral radiographs and MXA, and analysis included themeasurement of anterior and posterior heights from T4 to L4. We also obtained the vertebral morphometry of 200normal Korean women who underwent MXA between March 1995 and February 1996, though those with osteoporosis andother spinal lesions were excluded from this study. Thoracolumbar vertebral indexes were statistically correlatedwith age, height and bone mineral. RESULTS: There were no statistically significant differences in the heights ofspine phantom measured by MXA compared with actual size (mean difference=0.28mm). Simple radiographs weremagnified by 23.7% at a phantom-table distance of 15cm, and distortion ranged from 0.5% to 22.5%, depending onphantom level and phantom-table distance. In the study of volunteers, the magnification rate between a simpleradiograph and MXA was about 26.6%. Anterior height increased progressively from the thoracic to the lumbar spine,though posterior height peaked at L2, and L4 was less than anterior height. In Korean women, indices of vertebralmorphometry decreased significantly with aging, with the most prominent decrease occurring during the seventhdecade. The mineral density of spinal bone decreased markedly after the sixth decade. CONCLUSION: Radiographsshowed more magnification and distortion than did MXA, though between morphometric X-ray absorptiometry (MXA) andactual size, there was no significant difference. The vertebral morphometric indices of Korean women and referredbone mineral density may provide useful data for determining and evaluating follow-up changes in spinalmorphology.