Abstract
The purpose of this study was to explain how limited cone beam X-ray CT (Ortho-CT) is useful for the diagnosis of temporomandibular joint (TMJ) disorders. It uses a 4-inch image intensifier and small conical beam with an exposure field of 3.0cm in height and 3.8cm in diameter. Images in three sectional planes can be reconstructed from the data of one exposure in approximately ten minutes. Each voxel is an orthocubic figure whose sides are 0.136mm, and the imaging area consists of 240, 280, and 280 voxels respectively. Since the exposure field is small, the dose is very low compared with ordinary CT examination. The Ortho-CT and X-ray tomography were used in this study. The subjects were TMJ disorder patients. X-rays of 26 joints of 13 TMJ disorder patients were token to compare Ortho-CT with hypocycloidal tomography for the assessment of osseous structures of TMJ. Taking both mandibular condyle and articular eminence with one Ortho-CT is better than hypocycloidal tomography for observation of osseous structures. In conclusion, the results of this study suggested that Ortho-CT images are an excellent means for diagnosis of bone change of TMJ disorders.
