The temporomandibular joint (articulatio temporomandibularis) or TMJ is an articulation between the mandible and the temporal bone. The TMJ is a paired, modified, combined, bicondylar joint which is capable of a range of motions under the control and restraint of a number of muscles and ligaments.
It is formed by the:
- Articular surfaces of the mandibular fossa (the anterior part of mandibular fossa) which are concave.
- Articular tubercle which is convex.
- Head of the mandible.
Styloid or Eagle syndrome was described in 1937 by Watt Eagle. It is the ossification of the stylohyoid ligament or excessive elongation of the styloid process. The syndrome is associated with restricted movements of TMJ, pain during movements of the cervical part of the vertebral column and/or facial pain.
The following movements of the TMJ are possible:
- Angulation, lateral movements
- Circumduction – combination of all movements
Mastication is an initial part of the process in which food is prepared for digestion. It occurs in the oral cavity. It is a combination of movements like protrusion, retraction and lateral and medial rotation. The elevation is generated by the temporalis, masseter and medial pterygoid muscle. It is a very strong movement. The lateral pterygoid is connected with the depression, protrusion and angulation. The forward movements, such as protrusion, is generated by the medial and lateral pterygoid. The backward movements, such as retraction are connected with the temporalis and partly with the masseter, digastric and geniohyoid muscles. In angulation, the lateral and medial pterygoid play a significant role.
The Anterior Disc Displacement (ADD) gives changes in the smooth movements of the joint as a consequence of an anatomic disturbance in the relationship of the disc-condyle complex. In ADD the articular disc is positioned anteromedially to the condyle in the closed position. During opening the condyle slides over the posterior band of the disc. Clinically it is usually accompanied by a clicking sound during opening the mouth.