The temporomandibular joint ( TMJ ) are two joints that connect the jawbone to the skull. It is a bilateral synovial articulation between the temporal bones of the skull above and the mandible below; From these bones the name comes from.
Video Temporomandibular joint
Structure
The main components are joint capsule, articular disc, mandible condyles, articular surface of temporal bone, temporomandibular ligament, stilomandibular ligament, sphenomandibular ligament, and lateral pterygoid muscle.
Capsules and articular disks
The capsule is a solid fibrous membrane that surrounds the joint and combines the articular eminence. It attaches to the articular eminence, articular disc and mandibular condyle neck.
The unique feature of the temporomandibular joint is the articular disc. The disc consists of a solid fibrous connective tissue positioned between two bones that make up the joint. The temporomandibular joint is one of several synovial joints in the human body with an articular disc, the other being the sternoclavicular joint. The disk divides each joint into two. These two compartments are the synovial cavities, consisting of the upper and lower synovial cavities. Synovial membranes lining the joint capsule produce synovial fluid that fills these holes.
The central area of ​​the disc is avascular and has no innervation, and, on the other hand, the peripheral region has blood vessels and nerves. Few cells are present, but fibroblasts and white blood cells are present. The central area is also thinner but its consistency is denser than the peripheral area, which is thicker but has a more tender consistency. Synovial fluid in the synovial cavity provides nutrients for the avascular central area of ​​the disk. With age, the entire disk is thinned and may have cartilage in the middle, changes that can cause joint disturbance.
The lower joint compartment formed by the mandible and the articular disc is involved in the rotational motion - this is the jaw's initial movement when the mouth is open. The upper joint compartment formed by the articular disc and the temporal bone is involved in the translational motion - this is the jawbone secondary jaw movement when it is widely opened. The mandibular portion in pairs with the underside of the disc is the condyle and the temporal portion of the temporal bone pairs to the top surface of the disk is the articular fossa or the glenoid fossa or mandibular phosph.
Articular disk is a fibrous extension of the capsule between two joints. The disk serves as an articular surface against temporal bone and condyle and divides the joint into two halves, as described. This is a bikonet in the structure and attached to the medial and lateral condyle. The anterior portion of the disc divides in a vertical dimension, coinciding with the superior pterygoid lateral head insertion. The posterior part is also divided into vertical dimensions, and the area between the splits continues posteriorly and is called the retrodiscal tissue. In contrast to the disc itself, these connective tissue pieces are vascular and innervated, and in some cases anterior disk displacement, the pain felt during the mandibular movement is due to the condyle compressing this area against the articular surface of the temporal bone.
Ligaments
There are three ligaments associated with the temporomandibular joint: one major ligament and two minor. These ligaments are important because they define the border movement, or in other words, the furthest area of ​​movement, of the mandible. The movement of the mandible made over the functional boundaries permitted by the muscle attachment will produce painful stimuli, and thus, movement over this more limited boundary is rarely achieved in normal function.
- The main ligament, the temporomandibular ligament, is actually a lateral portion that thickens from the capsule, and has two parts: the outer oblique (OOP) and the inner horizontal part (IHP). The base of this triangular ligament is attached to the zygomatic process of the temporal bone and articular tubercle; its apex attached to the lateral side of the mandibular neck. This ligament prevents excessive retraction or moves backward from the mandible, a situation that may cause problems with joints.
- Two minor ligaments, stylomandibular and sphenomandibular ligaments are accessories and not directly attached to any part of the joint.
- The stylomandibular ligament separates the infratemporal (anterior) region from the parotid (posterior) region, and runs from the styloid process to the corner of the mandible; it separates the parotid and submandibular salivary glands. It also becomes tense when the mandible protrudes.
- Sphenomandibular ligaments run from the sphenoid spine to the mandibular lingula. The inferior alveolar nerve descends between the sphenomandibular ligament and the mandibular ramus to gain access to the foramen mandible. The sphenomandibular ligament, due to its attachment to the lingula, overlaps with the opening of the foramen. This is the rest of the embryonic lower jaw, Meckel's cartilage. Ligaments become accentuated and tight when the mandible protrudes.
Another ligament, called the "auto-mandibular ligament", connects the middle ear (malleus) to the temporomandibular joint: discomallear (or disco-malleolar) lopaments,
Supply of nerves
Temporomandibular joint sensory ranks come from aurikulotemporal branch and masseter from V 3 or mandible branch of the trigeminal nerve. It's just a sensory rating. Remember that motor is for muscle.
The specific mechanics of proprioception in the temporomandibular joint involve four receptors. Ruffini tip serves as a static mechanoreceptors that position the mandible. Pacinian corpus cells are dynamic mechanisms that accelerate movement during reflexes. Golgi tendon organs serve as static mechanoreceptors for the protection of ligaments around the temporomandibular joint. The free nerve endings are pain receptors to protect the temporomandibular joint itself.
Blood supply
Arterial blood supply is given by the branches of the external carotid artery, especially the superficial temporal branch. Other branches of the external carotid artery, the deep auricular artery, the anterior tympanic artery, the rising pharyngeal artery, and the maxillary artery, may also contribute to the arterial blood supply in the joint.
Development
Temporomandibular joint formation occurs approximately 12 weeks in utero when joint space and articular disc develops. About 10 weeks of future components of the fetus become apparent in the mesenchyme between the mandibular condylar cartilage and the developing temporal bone. Two gaps such as joint cavities and annoying disks make their appearance in the region at 12 weeks. Mesenchyme around the joints begin to form fibrous joint capsules. Very little is known about the importance of new muscle formation in joint formation. The superior head that develops from the lateral pterygoid muscle attaches to the anterior portion of the fetal disk. The disc also continues posteriorly through petrotympanic fissures and attaches to the middle ear malleus.
The growth center lies in the head of each mandible condyles before an individual reaches maturity. This growth center consists of hyaline cartilage under the periosteum on the surface of condylus articulation. It is the last center of bone growth in the body and is multidrug in its growth capacity, unlike the usual long bones. The cartilage area within this bone grows long with growth corresponding to the increase in the individual. Over time, cartilage is replaced by bone, using endokhondral ossification. This mandibular growth center in the condyle allows an increase in mandibular length required for larger permanent teeth, as well as for larger brain capacity of adults. This jaw growth also affects the overall shape of the face, and is thus mapped and referred during orthodontic therapy. When an individual reaches full maturity, the center of bone growth in the condyle has disappeared.
Maps Temporomandibular joint
Function
Each temporomandibular joint is classified as a "ginglymoarthrodial" joint because it is a ginglymus joint (hinging joint) and an arthrodial joint (shear). The mandible condyles articulate with the temporal bone in the mandibular fossa. The mandibular fossa is a concave depression in the squamous part of the temporal bone.
These two bones are actually separated by an articular disc, which divides the joint into two different compartments. The inferior compartment allows for the rotation of the condylar head around the momentary axis of rotation, corresponding to the first 20mm or more of the opening of the mouth. After the mouth is open to this limit, the mouth can no longer open without the superior compartment of the temporomandibular joint becoming active.
At this point, if the mouth continues to open, not only the condylar head rotates inside the lower compartment of the temporomandibular joint, but all equipment (condyle heads and articular disks) are translated . Although this has traditionally been described as a sliding movement forward and downward, on the anterior concave surface of the glenoid fossa and the posterior convex surface of the articular eminence, this translation actually amounts to rotation around other axes. This effectively results in an evolution that can be called the resultant axis of rotation of the mandible, which lies around the mandible foramen, allowing for low voltage environments for the blood vessels and innervation of the mandible.
The need for translation to produce further past clearance that can be achieved with a single rotation of the condyle can be demonstrated by placing the fist against the chin and trying to open the mouth more than 20 or more mm.
The resting position of the temporomandibular joint is not with toothed teeth. In contrast, muscle balance and proprioceptive feedback allow a physiological break for the mandible, the interocclusal cleansing chamber or the freeway, which is 2 to 4 mm between the teeth.
Jaw movement
The normal full jaw opening is 40-50 millimeters measured from the edge of the lower front teeth to the upper front teeth.
When measuring the range of vertical motion, the measurement should be adjusted for overbite. For example, if the measurement from the lower front teeth to the upper front teeth is 40 millimeters and the overbite is 3 millimeters, then the jaw opening is 43 millimeters.
During the movement of the jaw, only the mandible movements.
Normal movements of the mandible during function, such as mastication, or chewing, are known as visits. There are two lateral visits (left and right) and forward excursions, known as protrusions. Reversal of bulge is retraction.
When the mandible is transferred to the protrusion, the mandibular incisor, or mandibular front teeth, is removed so that they first come to the edge with the upper incisors (top) and then overtake it, resulting in a temporary underbite. This is done by translating the condyle downward of the articular eminence (at the top of the joint) without more than the slightest amount of rotation occurring (at the bottom of the joint), otherwise it is necessary to allow the mandibular incisors to come in front of the maxillary incisors without running into them. (This all assumes an ideal Class I or Class II occlusion, which is not entirely important for the lay reader.)
During chewing, the mandible moves in a certain way as described by two temporomandibular joints. The lateral moving side of the mandible is referred to as the working or rotating side, while the other side is referred to as the balancing or sacrificing side. The latter term, though somewhat outdated, is actually more precise, since they define the sides with the movements of each condyle.
When the mandible is transferred to the lateral journey, the working condyle condyle (the condyle on the side of the mandible moving outwards) only rotates (in the horizontal plane), while the balance side condyle does the translation. During actual functional chewing, when the teeth not only move from one side to the other, but also up and down when biting the teeth is inserted too, rotation (in the vertical plane) also plays a part in both condyls.
The mandible is moved principally by four chewing muscles: masseter, medial pterygoid, lateral pterygoid and temporalis. These four muscles, all innervated by the V 3 , or the trigeminal nerve mandibular division, work in different groups to move the mandible in different directions. The lateral pterygoid contraction acts to pull the disc and condylus forward in the glenoid fossa and down the articular eminence; thus, the action of this muscle serves to extend the jaw, with the help of gravity and the digastricus muscle also opens the jaw. Three other muscles close their mouths; masseter and medial pterygoid by pulling up the corners of the mandible and temporalis by pulling on the mandibular coronoid process.
Clinical interests
Pain
Temporomandibular joint pain is generally caused by one of four reasons.
- Myofascial pain syndrome syndrome, especially involving the chewing muscles. This is the most common cause.
- Internal disturbances, abnormal connections from disk to one of the other joint components. Disk displacement is an example of internal clutter.
- Osteoarthritis of the temporomandibular joint, degenerative joint disease on the articular surface.
- Temporal arteritis, considered a reliable diagnostic criterion.
Temporomandibular joint pain or dysfunction is sometimes referred to as "TMJ", and temporomandibular joint disorders (or dysfunction ) can be abbreviated to TMD. This term is used to refer to a group of problems involving temporomandibular joints and muscles, tendons, ligaments, blood vessels, and other tissues associated with them.
Although rare, other pathological conditions may also affect the function of temporomandibular joints, causing pain and swelling. These conditions include chondrosarcoma, osteosarcoma, giant cell tumors and aneurysm bone cysts.
Checkout
The temporomandibular joint can be felt in front of or inside the external acoustic meatus during mandibular movement. Auscultate joints can also be done.
Disc displacement
The most common disorder of the temporomandibular joint is the displacement of the disc. In essence, this is when the articular disc, attached anteriorly to the superior head of the lateral and posterior pterygoid muscles to the retrodiscal tissue, moves out from between the condyle and the fossa, so that the jaw bone and mandibular contacts are made on something other than the articular disk. This, as described above, is usually very painful, because unlike this adjacent network, the central part of the disc contains no sensory innervation.
In most cases of disturbance, the disc is transferred anteriorly to translation, or anterior and inferior sliding movement of the condyle forward in the fossa and down the articular eminence. At the opening, "pop" or "click" is sometimes audible and usually feels, too, showing the condylum moving back to the disc, known as "reducing the joint" ( disk displacement by reduction ). After closing, the condyle will slide from the back of the disc, then another "click" or "pop" at the point where the condyle is behind the disc. After clenching, the condyle condenses the bilaminar region, and the nerves, arteries and veins against the temporal fossa, causing pain and inflammation.
In disk displacement without reducing the disk remains anterior to the condylar head when opening. Mouth opening is limited and there is no "pop" or "click" sound when opening.
Congenital disorder
- Mandibular or skeletal aplasia
- Mandibular bone hypoplasia or skull bone
- Mandibular or cranial biliary hyperplasia
- Dyslexia of abnormal tissue development
Traumatic disorder
- mandible dislocation
- Fracture
- Subluxation
Inflammatory Disorders
- Synovitis
- Capsulitis
- Myositis
Degenerative Disorders
- Osteoarthritis
- Rheumatoid arthritis
Idiopathic Disorder
- Temporomandibular disorders (TMD, also called "temporomandibular joint pain syndrome syndrome") are TMJ pain and dysfunction and chewing muscles (the muscles that move the jaw). TMD does not fit into any of the categories of etiology because pathophysiology is poorly understood and it is a variety of disorders that are different from a multifactorial etiology. TMD accounts for the majority of TMJ pathology, and is the second most frequent cause of orofacial pain after toothache (ie toothache).
- Fibromyalgia
References
External links
- The American Association of Oral and Maxillofacial Surgeons (AAOMS) - The Temporomandibular Joint (TMJ)
- National Institute of Dental and Craniofacial Research, National Institutes of Health
- International College of Cranio Mandibular Orthopedics
Source of the article : Wikipedia
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