Practice Essentials
The temporal mandibular joint (TMJ) is the synovial joint that connects the jaw to the skull. These two joints are located just in front of each ear. Each joint is composed of the condyle of the mandible, an articulating disk, and the articular tubercle of the temporal bone. The movements allowed are side to side, up and down, as well as protrusion and retrusion. This complicated joint, along with its attached muscles, allows the movements needed for speaking, chewing, and making facial expressions.
Pain and functional disturbances related to the TMJ are common. [1, 2] Uyanik et al identifies the following three distinct causes of pain at the TMJ, which collectively fall under the broader term of TMJ syndrome [3] :
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Myofascial pain dysfunction (MPD) syndrome, which is pain at the TMJ due to various causes of increased muscle tension and spasm. It is believed that MPD syndrome is a physical manifestation of psychological stress. No primary disorder of the joint itself is present. Pain is secondary to events such as nocturnal jaw clenching and teeth grinding. Treatment is focused on behavioral modification as opposed to joint repair.
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Internal derangement (ID), where the problem lies within the joint itself, most commonly with the position of the articulating disc
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Degenerative joint disease, where arthritic changes result in degeneration of the articulating surfaces
See also Temporomandibular Disorders. For patient education information, see Temporomandibular Joint (TMJ) Syndrome.
Pathophysiology
The pathophysiology of TMJ syndrome is not entirely understood. It is believed that the etiology is likely multifactorial and arises from both local insults and systemic disorders. Local problems frequently arise from articular disc displacement and hereditary conditions affecting the structures of the joint itself, such as hypoplastic mandibular condyles. A study by Tallents et al found TMJ displacement in 84% of patients with symptomatic TMJ versus 33% of asymptomatic subjects. [4]
The TMJs can also be affected by conditions such as rheumatoid arthritis, juvenile idiopathic arthritis, [5] osteoarthritis, and diseases of the articular disks. In addition, hypermobile TMJs, nocturnal jaw clenching, nocturnal bruxism, jaw clenching due to psychosocial stresses, and local trauma also play a significant role.
A study of 299 females aged 18-60 years suggests that compared with nonsmokers, female smokers younger than 30 years had a higher risk of temporomandibular disorder than older adults. [6]
As described by Hegde, a strong understanding of how the trigeminal nerve innervates the TMJ and surrounding structures explains the pain and referred pain patterns of TMJ disorders. [7] Irritation of the mandibular branch (V3) of the trigeminal nerve results in pain locally at the TMJ and also to other areas of V3 sensory innervation, which include the ipsilateral skin, teeth, side of the head, and scalp.
Epidemiology
Frequency
United States
Currently, an estimated 10 million people have TMJ disorders, and roughly 25% of the population have symptoms at some point in their lives.
Mortality/Morbidity
The morbidity of the disorder is related to significant pain on movement of the jaw. While some patients' symptoms may resolve within weeks, others may have chronic symptoms that persist even with extensive therapy.
One study by Rammelsberg et al followed 235 patients over 5 years. [8] In this study, roughly one third of patients had completely resolved pain, one third had continuous pain over the 5 years, and one third had recurrent episodes with periods of remission.
Race-, Sex-, and Age-related Demographics
See the list below:
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No apparent association with race exists.
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Female-to-male ratio is roughly 4:1.
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Highest incidence of TMJ syndrome is in adults aged 20-40 years
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TMJ syndrome is found infrequently in the pediatric population
