A Radiological Study on the Bone Structures in the Functional Temporomandibular Joint

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An evaluation of abnormalities on radiograms of the temporomandibular joints (TMJs) depends on the inter-and intrasubjects differences in form of their bone structures. The aim of this radiologic study is to clarify the adaptive bone changes of the TMJs to habitual jaw movements, estimating the basic forms of the lateral aspects of the condylar heads just after the growth period of them and investigating a process of structural changes of the TMJs on the selective lateral tomograpms of the patients with temporomandibular joint disorders (TMD), and analyzing chewing cycles of the patients recorded by a Sirognatho Analyzing System II. The resutls were as follows ;(1) Flattening or a concavity was unexpectedly found on the posterior articular surface of the condylar heads of the patients with TMD by the selective lateral tomography as a routine radiographic examination of the TMJs.(2) With an incidence of about 30%, the concavity was found on the condylar head of 159 patients, even in eve … More ry age group on a radiological study. The result indicated that the concavity was not merely a aging, but probably an adaptive change in the patient with TMD.(3) A superimposing technique of simultaneous multisection tomograms was developed for the radiographic measurement of the TMJs. On a follow-up study, the technique proved that the change in shape of the condylar head and the spatial change of the mandible were interacted with each other. That is, antero-superior repositioning of the condylar head lead the condyle into the shortening.(4) Lateral aspects of the condylar head of the patients just after the growth period were classified into 6 groups. The first, significantly small and rounded group and the second, elongated group were considered to be a developmental anomaly due to the functional loading to the TMJs during jaw movements on their growth period.(5) Analysis of chewing cycles of TMD patients could not manifest the relationships between the adaptive changes of the condylar head and jaw movements. Further studies on jaw movements were required for the functional loading. Less