A method of producing roentgenograms of the temporomandibular joint

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B Y STUDYING THE literature on roentgenography of the temporomandibular joint, we find many methods of producing such roentgenograms described during the last twenty years. In the beginning of the thirties, Parma’ (Czechoslovakba) described the following method. The patient is placed with the median sagittal plane of the head in a vertical position. The cassette is also placed in a vertical p’lane as close as possible to the condyle area. The tube of the x-ray machine is directed in such a way that the central beam enters the head immediately in front of the external auditory meatus. Then the beam passes in a horizontal direction to the opposite glenoid fossa. The mouth is kept wide-open during the exposure. Steinhardt” (Germany) proceeded in a similar manner, with the exception that the central beam entered the head at a point situated 5 cm. in front of the auditory meatus and the same distance below a horizontal plane through the meatus. Steinhardt also had the patient’s mouth wide-open during the exposure. It is evident that, when employing one of the previously mentioned methods, we do not get such pictures of the joints as we require from the odontologic point of view. We need pictures in quite another plane. In order to study the various positions of the condyle in relation to the fossa and th.e eminentia, the central x-ray beam must coincide with the longitudinal axis of one of these parts. Higley” set about from this principle when elaborating his method. As a center of the area to be roentgenographed, he chose the crest of the eminentia. He examined a large number of skulls and cadavers in order to find out in which direction this crest runs in relation to a vertical plane through the external auditory meatus at a right angle with the Frankfort plane. He found the crest tcr have a backward inward angulation of 20 degrees to this plane. In relation to the horizontally situated Frankfort plane, the angulation was 6 to 8 degrees in. ward downward. Furthermore, Higley stated that the longitudinal axis of the fossa as well as that of the condyle were similarly directed in the majority of cases. Only certain variations of the latter could be observed. With these investigationx as a basis, Higley built a contrivance for making roentgenograms with the central beam coinciding with the longitudinal axis of the crest of the eminentia. From the scientific point of view, no objections to this method can be raised, and good pictures of the joint are obtained in most cases. Sometimes, however, bony processes of the base of the cranium overshadow the pictures, and, in these cases.