Temporomandibular joint (TMJ): anatomy, structure, characteristics

The temporomandibular joint (TMJ) plays a significant role in the performance of the chewing (which is responsible for thorough chewing of food and its further easier assimilation in the stomach) and articulation functions.

Outwardly, it is impossible to see the process of the joint work, but it performs tens of thousands of movements per day while eating, drinking and talking, breathing or facial movements (smile, laughter, anger, surprise, fear, irritation, yawning) tongue movements, cleansing the mouth cavity.

Thanks to this joint, a person can carry out motor actions to open, close the jaw, and move sideways.

If there is an imbalance in the temporomandibular joint, then there is a "skew" - an imbalance throughout the body from the side from which the joint is disturbed. In some diseases, you can see a characteristic facial expression that changes due to skewing.

Anatomical structure

TMJ - has a complex, but unique structure, it does not interfere with the functioning of the hearing organs, without touching the nerves, blood vessels. The joint has a paired, connected design, which makes the simultaneous movement of the left, right side synchronous.

The temporomandibular joint consists of: fossa, head, capsule, stylomandibular ligament, posterior articular, articular tubercle, disc.

The head of the lower jaw resembles an ellipse in shape, slightly elongated, this makes it possible to actively move the lower jaw in relation to the upper in different directions: pushing back and forth, left and right, up and down, chewing traffic.

The head bone is located at the end of the condylar processes, thanks to which the lower part has a movable support. The head has slight differences between an infant and an adult.

The composition of the bone changes - overgrowing with cartilage from the moment the first teeth appear and acquiring new functions with age (development of chewing reflexes, development of speech in a child). The head of the lower jaw has an individual size, shape, which depends on the characteristics of development, on human activity, age-related changes.

Mandibular fossa - formed between part of the temporal bone, tubercle and zygomatic process. The fossa of the lower part is separated from the ear canal by a thin one (its width along the entire perimeter of the bone is different - from 1 mm to 3-4 mm) a bone plate, from the tympanic cavity separates its posterior vault, which prevents the development of pathological processes.

The fossa is divided into 2 parts - extracapsular, intracapsular, limited by the zygomatic process, tympanic fissure, tubercle and spine of the cuneiform bone. It can change its shape with age, growth, development of the dentition.

The articular tubercle in infants is absent, begins to develop by the first year of life and is formed by 6-8 years. Has its own developmental characteristics, which depend on the health of the teeth, their safety.

In old age, the tubercle decreases due to the loss of teeth and deformation of the jaw. From the glenoid fossa, the tubercle is closer to the front, has a cylindrical protrusion, as well as a bulge in the sagittal direction and a concavity in the transverse direction.

The articular disc does not have nerve endings; its nutrition is carried out through the lymph and fluid of the periarticular tissues. It is attached by elastic connective tissue between the tubercle and the head. The disc consists of cartilaginous tissue in a biconcave shape. The thickness and shape of the disc depends on the type and shape of the mandibular fossa.

The capsule consists of fibrous and endothelial connective tissue, has a dense thick layer, high strength. Ligaments woven into the capsule - awl-mandibular, pterygo-mandibular, temporomandibular, wedge-mandibular, allow movement of the articular disc, the head.

Ligaments allow movements up, sideways, down, forward, restrict backward movement, strengthen and restrain stretching of the intra-mandibular joint. They play a significant role in the rigid fixation of the joint.

These ligaments include:

1. Extracapsular ligaments - Gruber's ligaments (stony-blade-shaped), which stretch behind the stony-scaly fissure from styloid process to the temporal bone, styloidmandibular, external and internal lateral, stylohyoid, wedge-mandibular.
2. Intracapsular ligaments - disco-mandibular medial and lateral, meniscus-temporal and jaw.

Anatomy and physiology of the maxillary joint. Video:

Innervation and blood supply

The innervation has an afferent (sensitive) character, providing organs and nerves with a connection with the central nervous system.

Innervation occurs through the chewing nerve, chin, branches of the ear, deep temporal, facial, lateral ligament, buccal nerve. Through the salivary gland it is innervated through the submandibular and ear ganglia.

The blood supply to the TMJ comes from different sources - blood vessels and arteries: the external branch of the carotid arteries, from the branch of the temporal artery, from the maxillary and ear arteries, as well as the pharyngeal ascending arteries. The outflow of blood occurs through the venous trunk of the mandibular vein.

Functional features

TMJ performs many functions and is the main one in the functioning of the chewing process, development, formation of speech, the sound apparatus of a person, the ability to make movements in different directions (left-right, forward-backward, vertically-horizontally).

Has specific functional features:

1. Consists of 2 connecting pieces: left-right, which have exactly the same structure and consist of a head, disc, tubercle, fossa, capsule and ligament. They are combined into one whole system of functioning, and perform all actions synchronously, in case of violation of synchronicity, dysfunctions occur.
2. It has a complex mechanism of work, which is embodied in the movements of the lower jaw, and not only in it, but as a transmitting impulse to the central nervous system. Its purpose is to control the chewing processes, which consist of 3 directions: receptor, chewing muscles, periodontal proprioceptors.
3. Thanks to the trifoliate nerve, there is a functional connection between the lower and upper dentition and the masticatory muscles, they reflect the biological mechanism of the TMJ.
4. The parallelism and simultaneity of movements is carried out by a complex unique reflex activity. In the dentoalveolar - facial system, its activity is carried out in 2 directions: indirect and direct contact of the teeth, their upper, lower row.

In the event of a violation or displacement of the constituent parts, dysfunction appears, which must be treated, otherwise the teeth are erased, the bite changes.

Types depending on the bite

Closing the teeth and their occlusion directly affect the work of the TMJ, and their change or deformation on the bite.

According to V.N. Trezubov's classification the bite is divided:

1. Functional (normal) - orthognathic bite, which allows the dentition to function fully.
2. Non-functional (abnormal) bite - in which the functioning of the dentition is disrupted as a result of deformation, with mechanical, anatomical disorders. There are several types of such a bite:
   • distal (prognathic), when the upper jaw protrudes above the lower, in this case the upper part is more developed or the lower one is poorly developed;
   • deep (incisal occlusion) - the incisors of the upper jaw overlap the incisors of the lower jaw;
   • crossbite and asymmetric development of the bones of the face, with it the rows of teeth of the upper and lower jaw intersect;
   • mesial bite, the opposite of the distal bite - the dentition of the lower jaw is pushed forward over the teeth of the upper jaw. In this case, the lower jaw is strongly developed and, on the contrary, the upper jaw is poorly developed;
   • open (vertical deocclusion), with it the teeth of the upper and lower jaw do not completely close in front, from the side.

Any malocclusion requires treatment and restoration to its normal state. If the bite is disturbed, then the person has a violation of the chewing function, the development of speech, and ENT diseases and dental problems may also occur.

Dysfunction

TMJ dysfunction is called Kostenko syndrome after the first researcher of functional joint pathologies.

It occurs as a result of a violation of the motor activity of the TMJ, which is carried out simultaneously on the right and on the left.

If violated, the left and right sides do not work simultaneously and asymmetrically.

TMJ diseases include: arthrosis, arthritis, synovitis, ankylosis, dislocations, tendonitis.

Causes

In case of violation of the TMJ function, it begins to work incorrectly, causing discomfort, pain.

The causes of dysfunction include:

• bite pathology;
• mechanical, traumatic damage to the jaw;
• surgical intervention, after which there were problems with disruption of the TMJ;
• stress;
• infection;
• anatomical abnormalities, genetic predisposition;
• pathologies associated with tooth wear;
• physical exercise;
• very hard food (teeth cracking of nuts).

Symptoms

Symptoms can be so slight at first that it is difficult to identify which disease is developing, but gradually they intensify, their number increases.

These symptoms include:

• strong painful sensations that can be given to the ear, head, teeth, gums;
• unusual sounds emanating from the jaw - crunching, grinding, clicking, popping, creaking;
• dizziness;
• hearing impairment;
• swelling of the face;
• loss of sleep, appetite;
• difficulty speaking, chewing food;
• squeezing, holding back the opening - closing of the jaw;
• tinnitus;
• subfebrile temperature;
• depressive state.

If such symptoms occur, a person should consult a dentist and a surgeon.

Treatment

The patient's appeal to the dentist will allow to identify the causes, eliminate them, as well as schedule the treatment and get advice.

To make a diagnosis, the patient is offered to undergo diagnostic procedures depending on the symptoms and the alleged causes. The doctor will make a history, palpate and prescribe one or more diagnostic methods: X-ray, CT, ultrasound, MRI, orthopantomography, gnatodynamometry, Doppler ultrasound, electromyography.

After the diagnosis, the doctor prescribes one or more types of treatment:

1. Drug treatment: steroidal, non-steroidal, glucocorticosteroid drugs in the form of tablets or injections.
2. Physiotherapy treatment: massage (jaw, neck, shoulders), myogymnastics, electrophoresis, darsonvalization, microwave and UHF, magnetotherapy, heat therapy in the form of various applications.
3. Surgical intervention: prosthetics, implantation, arthroscopy and other operations. After the operation, a bandage is put on to restrict the movement of the lower jaw.
4. Laser therapy.
5. Folk remedies: warm and cold compresses, decoctions of yarrow, burdock, propolis infusions.
6. Installation of braces, trainers, occlusal or acrylic splints, restoration of teeth, dental crowns, thereby restoring the normal bite height.
7. Limiting the movement of the jaws, reducing physical stress on the joint, a mode of complete silence and liquid soft food. Rest during a night's sleep, by positioning only on the back without a pillow (lateral or prone position can strain the TMJ).

Modern medicine in the dental field has stepped very far and allows you to solve problems with TMJ disorders without surgery.

Osteopathy and temporomandibular joint health. Video:

The main task of the dentist after treatment is to restore full movement of the jaw and the functionality of the neuromuscular complex. Self-treatment at home will not help to cope with the problem efficiently and without consequences.

Evolutionarily, it has developed that the TMJ of a person has played and plays a major role in satisfying the natural, physiological need - in nutrition, communication, expression of emotions.

Under stress or emotional stress, the 4 main muscles of the TMJ are affected, and their imbalance leads to other problems and disorders in the muscles of other joints of the human body, while reducing performance, deteriorating the quality life.

It is necessary to monitor the health and safety of the TMJ, especially to prevent infection, traumatic, mechanical damage.