Temporomandibular joint radiography in private dental clinic

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Patients with temporomandibular disorsers who visit on a private dental clinic increase year after year. To develope a new technique for the temporomandibular joint (TMJ) radiography using a panoramic x-ray unit in the clinic, basic principles of panoramic TMJ image formation were investigated from a clinical point of view. Mandibular condyle should be put into the image layr of the unit to get a sharp image of the TMJ.Intercondylar distances in 848 Japanese subjects were measured on submentovertical view to make clear the position of mandibular head relative to the effective image layr. The mean value of intercondylar distance was found to be constant in every decades more than 20 years old, that is, 101.1 (SD4.7) mm in female and 106.1 (SD5.3) mm in male respectively. To get a sharp image of TMJ,three size of image layr, 96,101 and 106mm in intercondylar distance, should be at least prepared for child, femal and male.In the second study, a optimum horizontal angulation of x-ray beam … More for TMJ radiography was experimentally surveyed. Eleven human dried speciemen with mandible fixed in edge to edge occlusion were rotated on axis clockwise or counter clockwise step by 5 degrees and exposed in every rotation. Thirteen images of each speciemen were examined and maximum rotation angle without superimposition of mastoid on the condyle was selected for a recommended projection. The angle proved to be less than 32 degrees antero-medially to the frontal plane in 9 out of 11 speciemen.In the third study, 72 autopsy mandibular condyles were radiographed in two different panoramic projections, of which angle is 18 degrees postero-medially (lateral mode) and 30 degrees antero-medially (oblique mode) to frontal plane. And then, accuracy, sensitivity and specificity of each projection were caluculated compared to tomographic findings as a gold standard. Accuracy, sensitivity and specificity of oblique mode in detecting an abnormal finding i.e. erosion are all higer than the lateral mode. On the contrary, those of lateral mode are higer than the oblique mode in detecting osteophyte formation.To get reliable informations of the TMJs with rotational panoramic unit alone, it should be equipped with the two modes. Less