Temporomandibular junction disorders (TMD) are a common problem for patients presenting to the primary care office. Symptoms may be acute or chronic. Patients may report a variety of complaints such as: painful clicking at the joint, difficulty opening the mouth or chewing, tenderness in the muscles around the joint, headaches, or tinnitus. Physical examination findings vary and may include palpable tenderness or spasm of the pterygoid muscles, palpable or audible clicking at the joint, wear and tear of tooth enamel, or dental malocclusion. Most TMDs respond well to conservative therapy, but some patients may benefit from more invasive treatments.
Key points
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Temporomandibular junction disorders (TMD) are a common cause of orofacial pain.
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Diagnosis of TMD is based on history and physical examination findings.
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Validated diagnostic questionnaires can help make the diagnosis of a TMD.
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Non-steroidal anti-inflammatory drugs are an effective first-line treatment for TMDs.
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Manual therapy and home exercises are beneficial for many patients with TMD.
Introduction
Temporomandibular disorders (TMDs) are common conditions that affect a significant portion of the population. They often present with orofacial or preauricular pain with or without painful jaw motion. Examiners may palpate tenderness in the masticatory muscles or hear or feel a click at the joint with jaw opening and closing. The etiology of this group of conditions can be multifactorial, and the clinical manifestations are variable. A thorough history and careful physical examination are essential for the appropriate diagnosis and treatment of TMDs. The Diagnostic Criteria for TMD (DC/TMD) is a useful evidence-based tool to help assess the condition. Treatments for TMDs range from conservative measures such as analgesics and education to more invasive therapies like surgery. The majority of reports that pain improve over time with non-invasive treatment.
History
Disease of the temporomandibular joint (TMJ) has been recognized and treated by physicians as far back as the 5th century. In the 1930’s, otolaryngologist James Costen described the condition as a spectrum of symptoms of the joint, ear, and sinuses. He proposed these symptoms were caused by nerve impingement from mechanical overbite, which contributed to the increasing role of dentists in evaluating the condition. In the 1950’s and 1960’s, investigators Schwartz and Laskin divided Costen’s syndrome into 2 categories: problems of the joint and problems of the muscles. In the 1980’s, a group of dentists proposed the umbrella term still in use today: TMDs.
Definitions
The TMJ is comprised of the mandibular condyle and the glenoid fossa of the temporal bone. A fibrocartilage disk in the middle of the joint is attached to the synovial lined joint capsule. Fig. 1 demonstrates the relationship of the involved structures. The masticatory muscles that surround the joint are primarily responsible for movement of the joint. Fig. 2 illustrates the more superficial muscles.
The interplay of joint, muscle, and bone contributes to the different symptoms of the disorder. The National Institute of Dental and Craniofacial Research states that, “TMDs are a group of more than 30 conditions that cause pain and dysfunction in the jaw joint and muscles that control jaw movement.”
Epidemiology
The number of people affected by TMDs is difficult to estimate and may vary, based on study methods. In a recent meta-analysis, the global prevalence of TMDs was 34%, was most common in middle aged adults, and more often affected females, as demonstrated in Fig. 3 .
Another recent analysis found that 4.8% of the United States (US) population reported pain in the region of the TMJ that could relate to a TMD. Prevalence was highest between the ages of 25 and 34 with a slightly higher rate in females. Non-Hispanic and White groups with higher income to poverty ratios were most likely to report jaw or face pain lasting more than 1 day in the 3 months prior to the study. Table 1 includes socio-demographic data from over 50,000 surveyed US adults from 2017 to 2018. TMDs are the second most common musculoskeletal condition resulting in pain and disability in the US, with an estimated annual cost or 4 billion dollars (about $12 per person in the US.)
| Population Group | % of Population | TMD Prevalence ∗ (%, 95% CL) |
|---|---|---|
| All adults | 100.0 | 4.8 (4.5, 5.0) |
| Age (years) | ||
| 18–24 | 11.8 | 4.2 (3.5, 5.0) |
| 25–34 | 17.8 | 4.9 (4.3, 5.4) |
| 35–44 | 16.4 | 5.2 (4.6, 5.8) |
| 45–54 | 16.7 | 5.4 (4.9, 6.0) |
| 55–64 | 16.8 | 5.1 (4.6, 5.7) |
| 65–74 | 12.1 | 3.7 (3.3, 4.2) |
| Sex | ||
| Female | 51.7 | 6.2 (5.9, 6.6) |
| Male | 48.3 | 3.2 (2.9, 3.5) |
| Region | ||
| Northeast | 17.8 | 4.4 (3.8, 4.9) |
| Midwest | 21.9 | 4.9 (4.3, 5.4) |
| South | 36.6 | 4.5 (4.1, 4.9) |
| West | 23.7 | 5.4 (4.9, 5.9) |
| Race | ||
| White | 77.7 | 5.0 (4.8, 5.3) |
| Black/African American | 12.4 | 3.6 (3.0, 4.2) |
| Native American | 1.2 | 4.1 (2.8, 5.5) |
| Asian | 6.4 | 3.0 (2.3, 3.7) |
| Other/multiple | 2.4 | 7.1 (5.4, 8.8) |
| Ethnicity | ||
| A: Hispanic | 16.2 | 4.4 (3.8, 5.0) |
| B: Not Hispanic | 83.8 | 4.8 (4.6, 5.1) |
| Income: Poverty ratio | ||
| <1.0 | 10.4 | 7.3 (6.5, 8.2) |
| 1.0–<2.0 | 16.1 | 5.9 (5.3, 6.5) |
| 2.0–<4.0 | 26.6 | 4.8 (4.4, 5.2) |
| ≥4.0 | 40.5 | 3.7 (3.3, 4.0) |
| Unknown | 6.4 | 4.5 (3.6, 5.4) |
∗ Jaw or face pain that lasted ≥1 day in the 3 months preceding the NHIS interview. From the authors’ analysis of data from n=52,159 participants in the 2017–2018 NHIS surveys.
Etiology
The cause and course of development of TMDs have been the subject of much debate, with ideas and research proposed from dentists, allopathic and osteopathic physicians, and physical therapists. TMDs may be divided into intra-articular problems and extra-articular muscle-based disorders. Differentiating between these 2 will inform diagnosis and treatment. Osteoarthritic joint changes, correlating with internal derangement of the disc, are key factors addressed by some research. The Orofacial pain: Prospective Evaluation and Risk Assessment study proposed that the biopsychosocial model best explains the multiple causes of this complex disorder. Because patient complaint and tissue pathology do not well correlate, it is proposed that some patients may have altered central nervous system pain processing related to specific inherited genes. Ongoing research at the molecular level, including hormone receptor polymorphisms and genetic polymorphisms in metabolic pathways may lead to new treatments.
Discussion
TMDs may present with symptoms including pain, joint noises, impaired jaw function, and locking. They may overlap with other pain syndromes such as headache and fibromyalgia. This variation contributes to the difficulty diagnosing and treating the condition. Joint noises may lead patients and clinicians to assume a TMD is present, but this assumption may lead to false diagnoses. Because the ear is so close to the TMJ, any joint noise is obvious. Asymptomatic disc displacement (DD) with reduction and without pain is very common and is usually benign, without progression that requires treatment.
TMDs are a leading cause of secondary otalgia in adults. If the history includes clicking with opening the jaw, accompanied by pain, and the physical examination reveals tenderness or crepitus about the joint, a TMD may be present. The most common TMDs include myalgia, myofascial pain, arthralgia, displacements, degenerative joint disease (DJD), subluxation, and headache related to TMD. Intra-articular TMDs involve DD and may occur with or without reduction. They may also include intermittent locking of the joint or limited mouth opening. DJD will have crepitus on examination. Subluxation is typically determined by history. Patients with myalgia will present with pain in the jaw, temple, ear, or preauricular region. They will also have pain on palpation of the masseter or temporalis muscles and may also experience pain with mouth opening. Myofascial pain is similar, but spreads beyond the site of palpation and may refer even further beyond the muscle examined. Patients with arthralgia will have pain on palpation of the lateral joint and with mouth opening. Patients with TMD related headache will have headache pain in the region of the temple that will be worsened with jaw movement.
The majority of TMDs is non-articular and involves muscular dysfunction. Patients may report a history of teeth grinding. Articular diseases such as arthritis and synovitis comprise another portion of disease. Patients with either dysfunction may report dull preauricular pain, joint noises, or restricted jaw motion. Pain that increases with chewing, yawning, or swallowing is considered pathognomonic for TMD. Pain may radiate to the ear or neck and may be made worse by chewing or prolonged opening of the mouth. On examination, the clinician may find joint clicking or locking, tenderness to palpate the muscles or joints, or reduced ability to open the mouth.
Patients with TMD complaints may share other pain conditions such as fibromyalgia, chronic fatigue syndrome, irritable bowel syndrome, chronic back pain, and headaches. TMD and migraine are associated in a bidirectional manner. TMD may cause or exacerbate headaches, which may in turn cause or exacerbate TMDs. The 2 may also be co morbid conditions, and the complex link is the subject of ongoing research. For some patients, particularly those with juvenile arthritis, symptoms may be severe enough to include pain with talking, difficulty eating, and alterations to facial appearance.
TMDs generally involve pain in the face and preauricular areas and may also include limitation to jaw movement. The examiner may find hyperalgesia on palpation of the mastication muscles or the joint and noises with motion. If any red flag signs or symptoms are present, further work up and referral is indicated. Some of those red flags and the differential to consider are included in Table 2 .
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