Temporomandibular Joint Osteoarthrosis and Temporomandibular Joint Hypermobility

For studying the relationship between condylar hypermobility of the temporomandibular joint (TMJ) and osteoarthrosis (OA), 13 patients with bilateral condylar hypermobility were evaluated clinically and radiographically, 30 years after non-surgical treatment. The evaluation included range of motion, joint and muscle tenderness to palpation, joint sounds and masticatory function. Radiographs of the TMJs were evaluated for the absence or presence of degenerative changes. The hypermobile group (HG) was compared with a control group (CG) (n= 13). The CG was evaluated in the same way as the HG. Statistics included t-tests (to compare ranges of motion in the HG over time and to compare ranges of motion in HG and CG), non-parametric tests (to compare tenderness of muscles and joints, joint sounds, masticatory function and radiographic changes over time in the HG). The tests were also used to compare the same variables between the HG and CG group. The groups' only difference was the presence of radiographic signs of OA. In the HG the number of joints with radiographic degenerative changes increased significantly over time and was significantly higher than the CG. Clinically and functionally, the HG and CG did not differ. Therefore, it is concluded that TMJ hypermobility is a subsidiary factor in the development of TMJ OA.     

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Understanding Temporomandibular Biomechanics

In all synovial joints normal function demands that sharp surface contact of the moving parts be maintained at all times. This is termed joint stability. Ordinary masticatory function imposes on the craniomandibular articulation a variety of mechanical forces which, if not counteracted, would separate the articulating parts and create a state of instability. An essential role of the articular discs is to maintain sharp contact of the joint surfaces during the full range of function—at rest as well as during empty-mouth movements, power strokes, and maximum intercuspation.

The mechanism by which stability is maintained in the temporomandibular joints is unique and complex. A full understanding of mandibular function (and dysfunction) depends largely on accurate knowledge of the biomechanics by which the articular discs maintain joint stability. Applying such information at a clinical level brings new meaning to symptoms that identify disc interferences. This knowledge improves diagnosis and makes therapy more effective.     

Temporomandibular joint sounds

The sounds of temporomandibular (TM) joints are described on the basis of a study of 191 patients with TM joint symptoms. Gnathosonic records were made for all of these patients, but synchronous mandibular movement records were made for only 30. A classification is proposed which takes into account the nature of the sounds (click or crepitus), their quality (hard or soft), their positions relative to mandibular movement (near, middle or wide) and whether the sounds occur on opening or closing of the jaws. Synchronous records of mandibular movement and of the sounds of the occlusion and TM joints are discussed. Possible causes of the sounds are suggested and reasons given for the alteration of the position of the sounds on opening and closing.     

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与颞下颌关节构成相关的器官包括：颞骨和下颌骨等骨组织，关节盘及相关韧带等特化的致密纤维结构和相关的肌肉。因此，颞下颌关节疾病包括累及上述组织、器官的各种疾病。