Temporomandibular joint

The temporomandibular joint ( temporo- mandibular articulation Latin ) is the movable connection between the mandible and the rest of the skull. In vertebrates, more specifically from the gnathostomes ( gnathostomata ) and with the exception of mammals, represents the temporomandibular joint, the joint between the articular Os and Os quadratum ago (primary jaw joint ). However, these bones are formed in mammals to ossicles and to form with them the joint between the hammer and anvil. The jaw joint of mammals is therefore a secondary jaw joint and is formed by the condyle of the mandible and the shed portion of the temporal bone.

Temporomandibular joint of mammals

The articulating bones Shares of the temporomandibular joint of mammals are the mandibular fossa ( glenoid fossa ) of the temporal bone and the head of the mandible ( head of the mandible ). The lower jaw pit is at the front by the articular tubercle and bounded behind by the processus retroarticularis. The joint head sits on the rolling projection ( condylar process ) of mandible ( ramus ).

The joint cavity of the temporomandibular joint is divided by a movable disk of cartilage, the discus, in an upper joint space ( the actual socket at the base of the skull down ) and a lower joint space ( the condyle of the mandible back ). In the upper half is mainly a sliding motion, in the lower half on the other hand a rotary movement instead.

Functional aspects in humans

Ideally centrally seated in the glenoid fossa, the cartilage discs between condyle and fossae are in the final bite both condyle. The joints should be symmetrical to each other, have the masticatory muscles on both sides of the same voltage and length and the teeth in the posterior region right and left uniform multi-point contacts. Each time swallowing unconsciously all these parameters are checked by the brain. If asymmetries (eg after placing too high a filling), an involuntary compensation mechanism in motion. Either the early contact is weggewetzt through increased rubbing the teeth - often identified by bare spots on freshly laid fillings - or the patient moves the lower jaw until he feels again on both sides of multi-point contacts to the teeth. However, there go the symmetry and both sides uniform tension of the muscles is lost, what can lead to a vicious circle (→ bruxism and craniomandibular dysfunction ).

With the analysis of misalignments of the jaw joint and the restoration of the ideal position, the dental specialty of gnathology deals. For determining the individual hinge axis axiography used.

Temporomandibular joint of birds

The jaw joint of birds consists of up to three joints, the mandibular articulationes:

• The articulation quadratomandibularis is functionally the most important joint and connects the articular bone of the lower jaw with the Os quadratum. In ducks, birds in the joint meniscus is stored.
• The articulation ectethmomandibularis is formed only with honey eaters and establishes the connection between the upper edge of the lower jaw with the Os ectethmoidale dar.