here have been many persons suffering from TMJ disorders with varying symptoms in temporo-mandibular joints (TMJ). Many devices for the X-ray examination have been made for the detection of the morphological changes in the osseous components of TMJ, and more than scores of radiographic methods have been reported. Panoramic radiography has. been also utilized to find out the morphological changes in osseous TMJ, as this kinds of machine have been developed. However, the panoramic methods seem to be rarely used in routine x-ray diagnosis of the TMJ, notwithstanding the fact that the method has a suitable angle of the x-ray beam for the osseous articular surface of the TMJ.
The purpose of this study is to establish the more useful and effective radiographic methods for the x-ray examination of TMJ by orthopantomography.
Experiments were performed as follows to investigate the role of orthopantomographyin x-ray examination of TMJ.
1. The locus of the rotation center, and the width and the center of the image layer of Panoramax 100-20 R were examined utilizing a test chart devised by the authors. Use ful parts of the image layer were selected on the basis of the relative positional relationship between the image layer and ear rods.
2. Various parts of the condylar head, articular fossa and articular eminence of the five dry skulls with different shape and different angle of the long axis of condylar head were marked with 0.5 mm copper wire. They were positioned on the selected image layer nd were examined by Panoramax 100-20 R. Then, the effects of the morphological variations of the TMJ to the radiographic image were examined and discussed. The anatomical landmarks of the TMJ were confirmed in the radiograms.
3. The investigation was carried out theoretically, whether the sharp images of dental arch and TMJ can be obtained on one film. The theoretical considerations were followed by the experiments on a dry skull.
4. Furthermore, this method was applied to several patients. As the results of a series of experiments and practices, it was found that the lateral part of the articular eminence and the most parts of the condylar head except medial one third were detected clearly with conventional orthopantomographic image of teeth.
It was evidenced that this orthopantomographic method was useful and effective in radiography for TMJ arthrotic patients, because the articular surface of the condylar head was projected tangenitially, that is, the outline of the image of condylar head was formed by a part of articular surface of osseous condylar head. Moreover, as TMJ was projected from antero-medial direction, there was minimum superimposition.
