STUDIES ON TRANSPHARYNGEAL TEMPOROMANDIBULAR JONT RADIOGRAPHY COMPARED WITH TRANSCRANIAL PROJECTION

Abstract

There has been an increased interest in the radiography of the temporomandibular joint (TMJ) in the last several years. Even though newer imaging techniques, such as computed tomography and magnetic resonance imaging, are available, most of radiographs of TMJ are still made on film with a standard x-ray machine.
The routine x-ray examination for the lateral view of the TMJ is taken on the oblique lateral transcranial projection. The disadvantage of this method is often the superimposition of the bony mandibular joint component on the petrous bone.
The study was made on the so-called transpharyngeal projection. This projection give an excellent profile view of the condyle without superimposition of bony structures.
Medial part of the condyle seemed to be well demonstrated by transpharyngeal method, while lateral part of the condyle to be demonstrated by transcranial method on dry skulls.
Clinically a central x-ray was directed 10° ventro-dorsally and 10° caudo-cranially to the TMJ in 20mm mouth opening.
Radiation doses from the transpharyngeal radiographs compared favorably to those from the transcranial. The superficial structures at the point of entry absorbed the greatent amount of radiation in both techniques evaluated, while other tissues of interest, such as thyroid gland and lens of the eye, received much smaller doses.
The transpharyngeal TMJ radiography does not show the upper structures of the joint clearly and can not be used to examine relationships of the condyle between the articular eminence, and the articular fossa, thus drastically restricting its usefulness. It serves best auxiliary film to the transcranial series.