Morphological causes of temporomandibular joint disorder

Abstract

In order to study the cause of temporomandibular joint disorder (TMD), I investigated the contribution of temporomandibular joint (TMJ) morphology to the development of TMD in a retrospective study of MR images of TMD patients and individuals free of clinical TMD symptonls. I examined retrospectively the axial MR images of 397 patients with clinical diagnosis of TMD, using 550 individuals without clinical TMD symptoms as controls. The distance between the bilateral mandibular heads, and the horizontal angulation of the mandibular heads was measured for each subject. The average horizontal angulation of the mandibular heads in the TMD group was 20.1° in males and 18.4° in females, while these values in the control group were 18.2° and 19.3°, respectively. The average distance between the bilateral mandibular heads was 102.8 mm in males and 97.4 mm in females for the TMD group, compared with 106.6 mm and 101.8 mm, respectively for the controls. There was no statistical correlation between the horizontal angulation and the distance between the bilateral heads at any age. However, there was a statistical difference of 100 mm in males and 95 mm in females for the distance between the bilateral heads for in the TMD group and the controls. These results indicate that this factor may be useful in discriminating between normal individuals and TMD patients. They further suggest that a narrow distance between the mandibular heads rather than their horizontal angulation may contribute to the etiology of temporomandibular joint disease.