[A standard projection for temporomandibular joint radiographs in oblique lateral projection]

A standard projection for temporomandibular joint radiographs in oblique lateral transcranial projection was determined by a clinical method. The individualized projections from 1644 TMJ radiographs, made with a fluoroscopic examination unit with image intensifier, were evaluated in a pilot study. A mean projection 20 degree cranial eccentric and 12 degree dorsal eccentric resulted. Reference planes were the Camper plane and the middle frontal plane. This projection, corrected in 22 degree/10 degree, was studied in a clinical study in order to test the readability of the radiographs of 100 temporomandibular joints. The readability of these radiographs was compared with that of radiographs obtained with an individualized projection. 81 radiographs out of 100 were well or very well readable, 7 were limitedly readable and 12 were unreadable. The number of radiographs in these last two categories could not be reduced by an individual angulation of the x-ray beam. Therefore anatomical reasons have to be considered to be responsible for the insufficient readability of these TMJ radiographs. This projection avoided superposition of the petrous portion of the temporal bone without giving an extreme view of the lateral slope of the condyle. From the evaluation of the 100 individualized projections resulted a mean projection 21 degree/10 degrees, which confirmed the projection 22 degrees/10 degrees used in this study. The projection 21-22 degrees/10 degrees turned out to be a most favourable projection for the dental office to make TMJ radiographs in connection with the diagnosis of the occlusion in patients with TMJ disorders.