Temporomandibular disorder (TMD) is a collective term that includes a number of clinical complaints involving the muscles of mastication, the temporomandibular joints (TMJs) and associated orofacial structures. Other commonly used terms are Costen’s syndrome, TMJ dysfunction, and craniomandibular disorders. TMDs are a major cause of nondental pain in the orofacial region and are considered a subclassification of musculoskeletal disorders. In many TMD patients the most common complaint is not with the TMJs but rather the muscles of mastication. Therefore, the terms TMJ dysfunction or TMJ disorder are actually inappropriate for many of these complaints. It is for this reason that the American Dental Association adopted the term temporomandibular disorder.
Signs and symptoms associated with TMDs are a common source of pain complaints in the head and orofacial structures. These complaints can be associated with general joint problems and somatization.
Approximately 50% of patients suffering with TMDs do not first consult with a dentist but seek advice for the problem from a physician. The family physician should be able to appropriately diagnose many TMDs. In many instances the physician can provide valuable information and simple therapies that will reduce the patient’s TMD symptoms. In other instances, it is appropriate to refer the patient to a dentist for additional evaluation and treatment.
Cross-sectional population-based studies reveal that 40% to 75% of adult populations have at least one sign of TMJ dysfunction (e.g., jaw movement abnormalities, joint noise, tenderness on palpation), and approximately 33% have at least one symptom (e.g., face pain, joint pain). Many of these signs and symptoms are not troublesome for the patient, and only 3% to 7% of the population seeks any advice or care. Although in the general population women seem to have only a slightly greater incidence of TMD symptoms, women seek care for TMD more often than men at a ratio ranging from 3:1 to 9:1. For many patients TMDs are self-limiting, or are associated with symptoms that fluctuate over time without evidence of progression. Even though many of these disorders are self-limiting, the health care provider can provide conservative therapies that will minimize the patient’s painful experience.
Signs and Symptoms
The primary signs and symptoms associated with TMD originate from the masticatory structures and are associated with jaw function (Box 1). Pain during opening of the mouth or during chewing is common.
Some persons even report difficulty speaking or singing. Patients often report pain in the preauricular areas, face, or temples. TMJ sounds are often described as clicking, popping, grating, or crepitus and can produce locking of the jaw during opening or closing.
Patients commonly report painful jaw muscles, and, on occasion, they even report a sudden change in their bite coincident with the onset of the painful condition.
|Common Primary and Secondary Symptoms Associated with Temporomandibular Disorders|
Facial muscle pain
Preauricular (TMJ) pain
TMJ sounds: jaw clicking, popping, catching, locking Limited mouth opening
Increased pain associated with chewing
Abbreviation: TMJ = temporomandibular joint.
It is important to appreciate that pain associated with most TMDs is increased with jaw function. Because this is a condition of the musculoskeletal structures, function of these structures generally increases the pain. When a patient’s pain complaint is not influenced by jaw function, other sources of orofacial pain should be suspected.
The spectrum of TMD often includes commonly associated complaints such as headache, neckache, or earache. These associated complaints are often referred pains and must be differentiated from primary pains. As a general rule, referred pains associated with TMDs are increased with any activity that provokes the TMD pain.
Therefore, if the patient reports that the headache is aggravated by jaw function, it could very well represent a secondary pain related to the TMD. Likewise, if the secondary symptom is unaffected by jaw use, one should question its relationship to the TMD and suspect two separate pain conditions. Pain or dysfunction due to nonmusculoskeletal causes such as otolaryngologic, neurologic, vascular, neoplastic, or infectious disease in the orofacial region is not considered a primary TMD even though musculoskeletal pain may be present. However, TMDs often coexist with other craniofacial and orofacial pain disorders.
Anatomy and Pathophysiology
The TMJ is formed by the mandibular condyle fitting into the mandibular fossa of the temporal bone. The movement of this joint is quite complex as it allows hinging movement in one plane and at the same time allows gliding movements in another plane.
Separating these two bones from direct articulation is the articular disk. The articular disk is composed of dense fibrous connective tissue devoid of any blood vessels or nerve fibers. The articular disk is attached posteriorly to a region of loose connective tissue that is highly vascularized and well innervated, known as the retrodiskal tissue. The anterior region of the disk is attached to the superior lateral pterygoid muscle.
The movement of the mandible is accomplished by four pairs of muscles called the muscles of mastication: the masseter, temporalis, medial pterygoid, and lateral pterygoid. Although not considered to be muscles of mastication, the digastric muscles also play an important role in mandibular function. The masseter, temporalis, and medial pterygoid muscles elevate the mandible and therefore provide the major forces used for chewing and other jaw functions. The inferior lateral pterygoid muscles provide protrusive movement of the mandible, and the digastric muscles serve to depress the mandible (open the mouth).
When discussing the pathophysiology of TMD one needs to consider two main categories: joint pathophysiology and muscle pathophysiology. Because etiologic considerations and treatment strategies are different for these conditions, they are presented separately.
Pathophysiology of Intracapsular TMJ Pain Disorders
Several common arthritic conditions such as rheumatoid arthritis, traumatic arthritis, hyperuricemia, and psoriatic arthritis can affect the TMJ. These conditions, however, are not nearly as common as local osteoarthritis. As with most other joints, osteoarthritis results from overloading the articular surface of the joint, thus breaking down the dense fibrous articular surface and ultimately affecting the subarticular bone. In the TMJ, this overloading commonly occurs as a result of an alteration in the morphology and position of the articular disk. In the healthy TMJ, the disk maintains its position on the condyle during movement because of its morphology (i.e., the thicker anterior and posterior borders) and interarticular pressure maintained by the elevator muscles. If, however, the morphology of the disk is altered and the diskal ligaments become elongated, the disk can be displaced from its normal position between the condyle and fossa. If the disk is displaced, normal opening and closing of the mouth can result in an unusual translatory movement between the condyle and the disk, which is felt as click or pop. Disk displacements that result in joint sounds might or might not be painful. When pain is present it is thought to be related to either loading forces applied to the highly vascularized retrodiskal tissues or a general inflammatory response of the surrounding soft tissues (capsulitis or synovitis).
Pathophysiology of Masticatory Muscle Pain Disorders
The muscles of mastication are a very common source of TMD pain. Understanding the pathophysiology of muscle pain, however, is very complex and still not well understood. The simple explanation of muscle spasm does not account for most TMD muscle pain complaints. It appears that a better explanation would include a central nervous system affect on the muscle that results in an increase in peripheral nociceptive activity originating from the muscle tissue itself. This explanation more accurately accounts for the high levels of emotional stress that are commonly associated with TMD muscle pain complaints. In other words, an increase in emotional stress activates the autonomic nervous system, which in turn seems to be associated with changes in muscle nociception.
These masticatory muscle pain conditions are further complicated when one considers the unique masticatory muscle activity known as bruxism. Bruxism is the subconscious, often rhythmic, grinding or gnashing of the teeth. This type of muscle activity is considered to be parafunctional and can also occur as a simple static loading of the teeth known as clenching. This activity commonly occurs while sleeping but can also be present during the day. These parafunctional activities alone can represent a significant source of masticatory muscle pain, and certainly bruxism in the presence of central nervous system–induced muscle pain can further accentuate the patient’s muscle pain complaints.
Because TMD represents a group of disorders, any of several etiologies may be associated. Problems arising from intracapsular conditions (clicking, popping, catching, locking) may be associated with various types of trauma. Gross trauma, such as a blow to the chin, can immediately alter ligamentous structures of the joint, leading to joint sounds. Trauma can also be associated with a subtler injury such as stretching, twisting or compressing forces during eating, yawning, yelling, or prolonged mouth opening.
When the patient’s chief complaint is muscle pain, etiologic factors other than trauma should be considered. Masticatory muscle pain disorders have etiologic considerations similar to other muscle pain disorders of the neck and back. Emotional stress seems to play a significant role for many patients. This can explain why patients often report that their painful symptoms fluctuate greatly over time.
Although most TMD patients do not have a major psychiatric disorder, psychological factors can certainly enhance the pain condition. The clinician needs to consider such factors as anxiety, depression, secondary gain, somatization, and hypochondriasis. Psychosocial factors can predispose certain people to TMD and can also perpetuate TMD once symptoms have become established. A careful consideration of psychosocial factors is therefore important in the evaluation and treatment of every TMD patient.
TMDs have a few unique etiologic factors that differentiate them from other musculoskeletal disorders. One such factor is the occlusal relationship of the teeth. Traditionally it was thought that malocclusion was the primary etiologic factor responsible for TMD. Recent investigations, however, do not support this concept. Still, in certain instances occlusal instability of the teeth can contribute to a TMD. This may be true in patients with or without teeth. Poorly fitting dental prostheses can also contribute to occlusal instability. The occlusal condition should especially be suspected if the pain problem began with a change in the patient’s occlusion (e.g., following a dental appointment).
History and Examination
All patients reporting pain in the orofacial structures should be screened for TMD. This can be accomplished with a brief history and physical examination. The screening questions and examination are performed to rule in or out the possibility of a TMD. If a positive response is found, a more extensive history and examination is indicated. Box 2 lists questions that should be asked during a screening assessment for TMD. Any positive response should be followed by additional clarifying questions.
|Recommended Screening Questionnaire for Temporomandibular Disorder|
|All patients reporting pain in the orofacial region should be screened for TMD with a questionnaire that includes these questions. The decision to complete a comprehensive history and clinical examination depends on the number of positive responses and the apparent seriousness of the problem for the patient. A positive response to any question may be sufficient to warrant a comprehensive examination if it is of concern to the patient or viewed as clinically significant by the physician.
1. Do you have difficulty, pain, or both when opening your mouth, for instance when yawning?
2. Does your jaw get stuck or locked or go out?
3. Do you have difficulty, pain, or both when chewing, talking, or using your jaws?
4. Are you aware of noises in the jaw joints?
5. Do your jaws regularly feel stiff, tight, or tired?
6. Do you have pain in or about the ears, temples, or cheeks?
7. Do you have frequent headaches, neckaches, or toothaches?
8. Have you had a recent injury to your head, neck, or jaw?
9. Have you been aware of any recent changes in your bite?
10. Have you been previously treated for unexplained facial pain or a jaw joint problem?
Abbreviation: TMD = temporomandibular disorder.
Patients experiencing orofacial pain should also be briefly examined for any clinical signs associated with TMD. The clinician can easily palpate a few sites to assess tenderness or pain as well as assess for jaw mobility. The masseter muscles can be palpated bilaterally while asking the patient to report any pain or tenderness. The same assessment should be made for the temporal regions as well as the preauricular (TMJ) areas. While the examiner’s hands are over the preauricular areas, the patient should repeatedly open and close the mouth. The presence of joint sounds should be noted along with whether these sounds are associated with joint pain.
A simple measurement of mouth opening should be made. This can be accomplished by placing a millimeter ruler on the lower anterior teeth and asking the patient to open as wide as possible. The distance should be measured between the maxillary and mandibular anterior teeth. It is generally accepted that less than 40 mm is a restricted mouth opening.
It is also helpful to inspect the teeth for significant wear, mobility, or decay that may be related to the pain condition. The clinician should examine the buccal mucosa for ridging and the lateral aspect of the tongue for scalloping. These are often signs of clenching and bruxism. A general inspection for symmetry and alignment of the face, jaws, and dental arches may also be helpful. A summary of this screening examination is shown in Box 3.
|Recommended Screening Examination Procedures for Temporomandibular Disorder|
|All patients with face pain should be briefly screened for TMD using this or a similar cursory clinical examination. The need for a comprehensive history and clinical examination depends on the number of positive findings and the clinical significance of each finding.
1. Palpate for pain or tenderness in the masseter and temporalis muscles.
2. Palpate for pain or tenderness in the preauricular (TMJ) areas.
3. Measure the range of mouth opening. Note any incoordination in the movements.
4. Auscultate and palpate for TMJ sounds (i.e., clicking or crepitus).
5. Note excessive occlusal wear, excessive tooth mobility, buccal mucosal ridging, or lateral tongue scalloping.
6. Inspect symmetry and alignment of the face, jaws, and dental arches.
Abbreviation: TMJ = temporomandibular joint.
Most recent studies suggest that TMDs are generally self-limiting and symptoms often fluctuate over time. Understanding this natural course does not mean these conditions should be ignored. TMD can be a very painful condition leading to a significant decrease in the patient’s quality of life. Understanding the natural course of TMD does suggest, however, that therapy might not need to be very aggressive. In general, initial therapy should begin very conservatively and only escalate when therapy fails to relieve the symptoms.
When the physician identifies a patient with a TMD, he or she has two options. The physician can elect to treat the patient or refer the patient to a dentist who specializes in TMD for further evaluation and treatment. The decision to refer the patient should be based on whether the patient needs any unique care provided only in a dental office. The following are some indications for referral to a dentist:
• History of trauma to the face related to the onset of the pain condition
• The presence of significant TMJ sounds during function
• A feeling of jaw catching or locking during mouth opening
• The report of a sudden change in the occlusal contacts of the teeth
• The presence of significant occlusal instability
• Significant findings related to the teeth (e.g., tooth mobility, tooth sensitivity, tooth decay, tooth wear)
• Significant pain in the jaws or masticatory muscles upon awakening
• The presence of an orofacial pain condition that is aggravated by jaw function and has been present for more than several months The specific therapy for a TMD varies according to the precise type of disorder identified. In other words, masticatory muscle pain is managed somewhat differently than intracapsular pain. Generally, however, the initial therapy for any type of TMD should be directed toward the relief of pain and the improvement of function. This initial conservative therapy can be divided into three general types: patient education, pharmacologic therapy, and physical therapy.
It is very important that patients have an appreciation for the factors that may be associated with their disorder, as well as the natural course of the disorder. Patients should be reassured, and if necessary, convinced by appropriate tests, that they are not suffering from a malignancy. Properly educated patients can contribute greatly to their own treatment. For example, knowing that emotional stress is an influencing factor in many TMDs can help the patient understand the reason for daily fluctuations of pain intensity. Attention should be directed toward changing the patient’s response to stress or, when possible, reducing exposure to stressful conditions. Patients with pain during chewing should be told to begin a softer diet, chew slower, and eat smaller bites. As a general rule the patient should be told “if it hurts, don’t do it.” Continued pain can contribute to the cycling of pain and should always be avoided. The patient should be instructed to let the jaw muscles relax, maintaining the teeth apart. This will discourage clenching activities and minimize loading of the teeth and joints.
When pain is associated with a clicking TM joint, the patient should be informed of the biomechanics of the joint. This information often allows the patient to select functional activities that are less traumatic to the joint structures. For example, some patients may report that the pain and clicking are less when they chew on a particular side of the mouth. When this occurs, they should be encouraged to continue this type of chewing.
Pharmacologic therapy can be an effective adjunct in managing symptoms associated with TMDs. Patients should be aware that medication alone will not likely solve or cure the problem.
Medication, however, in conjunction with appropriate physical therapy and definitive treatment, does offer the most complete approach to many TMD problems. Mild analgesics are often helpful for many TMDs. Control of pain is not only appreciated by the patient but also reduces the likelihood of other complicating pain disorders such as muscle co-contraction, referred pain, and central sensitization.
Nonsteroidal antiinflammatory drugs (NSAIDs) are very helpful with many TMDs. Included in this category are aspirin, acetaminophen (Tylenol), and ibuprofen. Ibuprofen (Motrin, Advil, Nuprin) is often very effective in reducing musculoskeletal pains. A dosage of 600 to 800 mg three times a day for 3 to 5 days commonly reduces pain and stops the cyclic effects of the deep pain input. For patients with gastrointestinal issues, short-term use of a cyclooxygenase-2 (COX-2) inhibitor such as celecoxib (Celebrex) can also be useful.
In many patients with TMD, symptoms are relieved with very simple physical therapy methods. Simple instructions for the use of moist heat or cold can be very helpful. Surface heat can be applied by laying a hot, moist towel over the symptomatic area. A hot water bottle wrapped inside the towel will help maintain the heat. This combination should remain in place for 10 to 15 minutes, not to exceed 30 minutes. An electric heating pad may be used, but care should be taken not to leave it on the face too long. Patients should be discouraged from using the heating pad while sleeping because prolonged use is likely.
Like thermotherapy, coolant therapy can provide a simple and often effective method of reducing pain. Ice should be applied directly to the symptomatic joint or muscles and moved in a circular motion without pressure to the tissues. The patient will initially experience an uncomfortable feeling that will quickly turn into a burning sensation. Continued icing will result in a mild aching and then numbness.
When numbness begins the ice should be removed. The ice should not be left on the tissues for longer than 5 minutes. After a period of warming a second cold application may be desirable.
The physician should be aware that many TMDs respond to the use of orthopedic appliances such as occlusal appliances, bite guards, and splints. These appliances are made by the dentist and are custom fabricated for each patient. Several types of appliances are available.
Each is specific for the type of TMD present. The dentist should be consulted for this type of therapy.
Other Therapeutic Considerations
Sometimes TMDs become chronic and, as with other chronic pain conditions, might then be best managed by a multidisciplinary approach. If the patient reports a long history of TMD complaints, the physician should consider referring the patient to a dentist associated with a team of therapists, such as a psychologist, a physical therapist, and even a chronic pain physician. Generally, patients with chronic TMD are not managed well by the simple initial therapies discussed in this chapter. Often other factors, such as mechanical conditions within the TMJs or psychological factors, need to be addressed. The physician who attempts to manage these conditions in the private practice setting can become very frustrated with the results. It is therefore recommended that if the patient’s history suggests chronicity or if initial therapy fails to reduce the patient’s symptoms, referral is indicated.
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