Temporomandibular joint

Eva Rudolf-Müller is a freelance writer in the medical team. She studied human medicine and newspaper sciences and has repeatedly worked in both areas - as a doctor in the clinic, as a reviewer, and as a medical journalist for various specialist journals. She is currently working in online journalism, where a wide range of medicine is offered to everyone.

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The temporomandibular joint (articulatio temporomandibularis) enables the lower jaw to move against the upper jaw and allows food to be chewed and minced in the oral cavity. The temporal bone and the mandibular fossa form the joint socket in which the joint head (caput mandibulae) of the lower jaw is movably seated. Read everything you need to know about the temporomandibular joint: anatomy, function, important diseases and injuries!

What is the TMJ

The temporomandibular joint consists of the joint head, the joint socket, a joint cusp, a joint disc and the joint capsule.

The joint head (caput mandibulae) on the articular process of the lower jaw has a cylindrical shape and is covered by cartilage on the front side. Above it, in the joint cavity surrounded by a joint capsule, lies a joint disc made of cartilage (discus articularis). It divides the joint cavity into two sections.

The mandibular fossa of the temporal bone functions as the joint socket. It is covered in cartilage in the front area. In front of it lies the small articular cusp (tuberculum articulare ossis temporalis).

The great mobility of the temporomandibular joint is made possible by the joint capsule, which consists of elastic fibers and connective tissue. It is so wide and slack that the lower jaw can even “dislocate” (luxate) without tearing.

The temporomandibular joint in newborns and the elderly

The joint socket in newborns is only flat. In toothless old people, the flat socket and the articular cusp are increasingly decreasing. The opening and closing of the mouth then takes place exclusively via a hinge movement.

What is the function of the temporomandibular joint?

The movements of the temporomandibular joint are primarily used to chew and chew food.

The mechanics of the temporomandibular joint are quite complicated, as it is to be understood as a combination of two joints: A lower joint (discomandibular hinge joint) and an upper joint (discotemporal sliding joint) together cause a kind of "rotary sliding". The right and left jaw joint always work together.

When the jaw is closed and there is no chewing motion, the teeth do not touch. The joint head then lies together with the disc in the anterior part of the joint fossa and on the posterior part of the joint cusp.

Hinge movement

The opening and closing of the mouth is a combination of a hinge and a sliding movement. It begins with a hinge movement in which the disc on the joint cusp slides forward and down and the angle of the jaw moves backwards, without articulation of the teeth. The reverse movement occurs when closing the mouth. The lower (discomandibular) hinge joint is responsible for this hinge movement.

Slide or slide movement

The lower jaw is pushed back and forth in the upper (discotemporal) sliding joint, guided by the teeth. Here the disc with the joint head slides forward on the joint cusp. The condition, shape and position of the teeth play a role in this movement of the temporomandibular joint. In the case of a severe overbite, the joint must first be opened a little so that the incisors of the lower jaw can pass those of the upper jaw.

Sideways or grinding movements

The teeth are also involved in sideways or grinding movements. One of the joint heads rotates around a vertical axis in the joint socket, while the other rotates forward on the joint cusp, causing the rows of teeth on this side to gape apart. The chin is moved to the opposite side. The movements take place alternately in the two jaw joints.

Where is the temporomandibular joint located?

The temporomandibular joint is the articulated connection between the temporal bone (os temporale) - a large, paired bone on the lateral skull wall - and the arched lower jaw.

What problems can the temporomandibular joint cause?

Arthrosis of the temporomandibular joint occurs as a result of damage to the articular cartilage. This can result from multiple dislocations (dislocation), injuries or inflammation of the temporomandibular joint. When the mouth is opened - painlessly - the lower jaw deviates to the healthy side (bonnet position). A typical cracking of the joints occurs during the opening of the mouth.

The temporomandibular joints can cause headaches, back pain, tinnitus or other complaints. Badly fitted tooth fillings or crowns, teeth grinding, stress or a crooked posture permanently damage the jaw joints. This causes the chewing muscles to cramp, which can send painful signals to all possible areas of the body. One then speaks of a temporomandibular joint syndrome (TMG syndrome).

If the joint head moves in front of the joint cusp with the mouth very wide open, the jaw may lock - the mouth can no longer be closed. In the opposite case, the mouth can no longer be opened with a so-called jaw clamp.

The temporomandibular joint can be broken if you fall or are hit in the face.

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