Temporomandibular joint: characteristics, anatomy and diseases

The mandible is an odd, flat, symmetrical and central bone located in the lower part of the face. It may look like just another bone, but without a doubt, it is one of the most important bone structures in humans. Thanks to the mandibular complex we are able to chew food and, in addition, we have developed a complex communication system based on it.

Without going any further, disorders in the craniomandibular joint complex not only result in difficulty eating, but also They can cause vertigo, dizziness, tinnitus, headaches, communication problems and many other events related to the head and/or ears. This type of pathology is suffered by up to 12% of the population, being much more prevalent in young people.

To understand the anatomy, functionality and possible failures of the chewing and speaking process, we must describe deep into the temporomandibular joint (TMJ), which allows this bone to move correctly. We tell you about it from both an anatomical and a medical approach, since pain in the maxillofacial area is very common in the general population and deserves to be known.

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What is the temporomandibular joint?

The temporomandibular joint is, as its name suggests, the articular element that joins the temporal bone and the mandible. It is a synovial joint (which allows movement) of the bicondylar type (when the heads of two bones fit over the other to generate a joint). It is a unique type of joint in the whole body, since both components work as a unit and, In addition, it is one of the very few mobile joint structures that can be found in the head of the humans.

We can differentiate various anatomical sections in this striking articular portion. We tell you about their particularities in the following lines, but you cannot forget that each of them is part of a homogeneous and unitary whole at a functional level:

• Capsule: it is a thin and diffuse envelope that is inserted into the bony surfaces of the vicinity. It allows a high range of movements and biological executions.
• Articular disc: it is composed of a fibrocartilaginous tissue that is positioned between the head of the mandibular condyle and the mandibular fossa. Its diameter is 2 to 3 mm, depending on the area analyzed.
• Ligaments: There are three different ligaments included in the temporomandibular joint (TMJ), one major and two minor.
• Nervous structures: the sensory innervation of this structure comes from the auriculotemporal and masseteric nerve, both branches of the trigeminal.
• Blood supply: Blood with nutrients and oxygen comes from the external carotid artery, which branches off from the common carotid.

The aforementioned ligaments are particularly noteworthy, since thanks to them the movements of the edges of the mandible, that is, those positions that can be adopted without suffering pain of a muscular nature in a situation of normal. The major ligament is called the "temporomandibular ligament," while the two minor ones are known as the stylomandibular and sphenomandibular ligaments..

As we have said briefly in previous lines, the blood supply comes from the superficial temporal artery and the artery maxilla, both being branches of the bifurcation of the external carotid artery, which in turn is the product of the bifurcation of the carotid proper. This artery is essential for survival in humans because, as a whole, it is responsible for blood perfusion to a large part of the brain.

On the other hand, the auriculotemporal and masseteric nerves sensory innervate the temporomandibular joint. Both arise as collateral branches of the mandibular nerve (V3), the largest of the three branches that converge on the trigeminal. In any case, it should be noted that these nervous structures are purely sensitive, since the motor fraction is in charge of the nerves associated with the skeletal muscles that surround the area.

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Functions of this jaw joint

When the human being's mouth opens, there is a combination of movements: a rotational one from the discomandibular space and a translational one, in the discotemporal space. The condylar process performs rotation and translation movements (in that order) thanks to the presence of muscular and ligamentous structures associated with the articular elements.

In addition to the mechanical actions of opening and closing the mouth, these complexes allow movements of protrusion, retrusion, laterality, and combinations of all of them. All these mechanical efforts and positions are linked to actions as basic in the human being as chewing, sucking, swallowing, speaking, gesturing, breathing, opening the mouth and maintaining the correct pressure in the middle ear. Undoubtedly, the temporomandibular joint plays an essential role in almost all the typical processes of the human being, which we carry out unconsciously.

Pathologies of the temporomandibular joint

We have narrated how important this synovial joint is for our species, so you can imagine that its failures are more than evident in the day-to-day of patients, even during the most difficult tasks. trifles. First of all, it should be noted that up to 25% of the population experiences symptoms of temporomandibular pathologies (TMD) at some point. In any case, curiously, only 5-7% seek help after the appearance of these ailments.

The etiology of TMD is multifactorial. Multiple theories have been proposed, such as mechanical displacement, osteoarthritis, failure at the muscle, physical-psychological factors, events of a social nature and various interactions between some or all of them. Anyway, We can group the typologies of the disease into three possible general causes:

• Predisposing factors: are the events that lead to the appearance of TMD or orofacial pain. Within them, genetic disorders, systemic problems, psychological pathologies and structural deformities are conceived.
• Initiating factors: a blow or continuous excessive efforts of the temporomandibular joint can lead to its degradation.
• Perpetuating factors: Muscle stress and certain metabolic problems can slow joint healing if the joint has been damaged in the past.

One of the major implicated in temporomandibular joint disorders is bruxism. This silent pathology is suffered by up to 70% of the population at any given place and time, and is defined as the involuntary jaw clenching and teeth grinding, especially at night when these movements are unconscious.

It is estimated that up to 52% of people with bruxism are positive before certain tests of stress, anxiety and depression. Whenever the wear of the structures involved is accompanied by pain or sensitivity, it is considered pathological, so "letting go" is never an option: if a patient ignores wear/inflammation/injury and other events in the temporomandibular joint, may lose the ability to eat properly and require a surgery.

In addition to bruxism, it should be noted that arthritis, arthralgia, synovitis, capsulitis, osteoarthritis, systemic arthritis and many other events can cause dysfunction of the temporomandibular joint. In general, anything that damages bones, tendons, synovial fluid, and muscles involved in this very special gear for life can jeopardize the proper functioning of the TMJ.

A person with TMJ disorders often perceives one or more of the following symptoms: pain in the jaw (more specifically in the area near the ear), difficulty chewing/yawning and severe pain when trying, chronic discomfort inside the ear or on its edges and, finally, total blockage of the joint, which implies a total impossibility to open or close the mouth.

Summary

As you will have been able to verify along these lines, the temporomandibular joint (TMJ) It is one of the most important joint formations in the entire body., since events as essential to life as eating, speaking or breathing are totally or partially conditioned by it. Therefore, it is necessary to take care of it and see a doctor promptly at any sign of prolonged facial pain.

There are treatments to alleviate the discomfort of TMJ syndromes, both medically and physiotherapy. For example, pain relievers, tricyclic antidepressants, muscle relaxants, night splints, and sessions to learn to manage stress and other altered states can greatly help patients with these ailments. If you know you have a problem related to the temporomandibular joint, don't let it be: your condition has a solution.

Bibliographic references:

• Temporomandibular joint (TMJ): syndrome, symptoms and treatments, Maxillofacial Institute. Collected on March 20 in https://www.institutomaxilofacial.com/es/2018/11/04/articulacion-temporomandibular-atm-sindrome-sintomas-y-tratamientos/
• Bordoni, B., & Varacallo, M. (2019). Anatomy, head and neck, Temporomandibular Joint. StatPearls [Internet].
• Maini, K., & Dua, A. (2020). Temporomandibular Joint Syndrome. StatPearls [Internet].
• Murphy, M. K., MacBarb, R. F., Wong, M. E., & Athanasiou, K. TO. (2013). Temporomandibular joint disorders: A review of etiology, clinical management, and tissue engineering strategies. The International journal of oral & maxillofacial implants, 28(6), e393.
• Prevalence of TMJD and its Signs and Symptoms, NIH. Collected on March 20 in https://www.nidcr.nih.gov/research/data-statistics/facial-pain/prevalence#:~:text=The%20prevalence%20of%20temporomandibular%20joint, are%20higher%20among%20younger%20persons.
• Temporomandibular Joint Disorders, Mayo Clinic. Collected on March 20 in https://www.mayoclinic.org/es-es/diseases-conditions/tmj/symptoms-causes/syc-20350941
• Temporomandibular Joint Disorders, Medlineplus.gov. Collected on March 20 in https://medlineplus.gov/spanish/temporomandibularjointdysfunction.html