Temporomandibular Disorders: Introduction
Temporomandibular disorders (TMDs) are a set of musculoskeletal disorders affecting the temporomandibular joint (TMJ), the masticatory muscles, or both. TMDs comprise many diverse diagnoses with similar signs and symptoms affecting the masticatory system, which can be acute, recurrent, or chronic. TMDs are rarely life threatening, but can impact heavily on an individual’s quality of life. Studies show that about 3–7% of the population need treatment.
TMDs occur disproportionately in women of childbearing age in a ratio of 4:1 to 6:1, and the role of estrogens seems to show an association. The prevalence drops off dramatically for both men and women after age 55.
The cause of TMD is variable and uncertain, and it is thought to be multifactorial in most cases. Genetic factors have recently been implicated. Most factors are not proven causal factors, but they are associated with TMDs. Predisposing factors increase the risk of TMDs. Predisposing factors are trauma, both direct (eg, blows to the jaw) and indirect (eg, whiplash injuries), and stress. Microtrauma is caused by clenching and grinding of the teeth. Stress can be a predisposing factor owing to the disruption of restorative sleep and the increase of nocturnal bruxism. Trauma and stress are also precipitating factors.
Perpetuating factors that sustain a TMD are stress, poor coping skills, harmful habits such as clenching and grinding, and poor posture. Nonrestorative sleep also may be a major factor in the perpetuation of chronic jaw pain.
Bruxism, or grinding the teeth during sleep, has been thought to be a predisposing, precipitating, and perpetuating factor. Bruxism can involve excessive activation of the masticatory muscles and excessive loading of TMJs, which can be a factor in the recovery of some patients, whereas in others bruxism does not seem to be a factor. In studies, bruxism has not been clearly demonstrated as a cause of TMD. Some individuals who severely grind their teeth do not have any signs or symptoms of TMD.
Dental and occlusal origins are not generally accepted, and the scientific evidence does not support their causal relationship. Experimental occlusal interferences have been placed with no evidence of TMD symptoms. There is no evidence of a higher incidence of TMD with any type of malocclusion, and significant proportions of the population have occlusal discrepancies without any TMD pain.
Whiplash has been thought to be a precipitating factor in the development of TMD. There is very little evidence that a noncontact injury can cause damage to the TMJ. However, many patients claim muscle and joint pain after a whiplash injury. The pain may be referred from the strained sternocleidomastoid muscle, which often refers pain to the ear, or it may be due to injuries to other cervical muscles and ligaments.
Disc displacement has been considered a pathologic condition, but many studies have shown that from 30% to 50% of populations have reducing discs. Most of these individuals have no history of TMJ pain or dysfunction. Disc displacement may be a normal biological variation. Clicking joints are not necessarily painful or pathologic. Studies reporting on the long-term follow-up of patients with disc displacement show the majority are asymptomatic 30 years later (Figure 26–1).
The most common TMD complaints are jaw, face, and head pain of moderate intensity. Limited opening, catching or sticking, and locking of the mandible are common functional complaints. Patients often have complaints of joint noises, such as clicking, popping, and grating when the mandible is opened or closed. Patients also have perceived complaints of global headache and neck and shoulder pain that are not related to jaw function. Some patients present with unexplained complaints of tinnitus, ear fullness, hearing loss, and dizziness. Complaints of abnormal tooth wear, tooth sensitivity, and teeth not meeting correctly are often expressed.
Magnetic resonance imaging (MRI) reveals hard bony tissue as well as soft tissue abnormalities. Computed tomography (CT) scans are useful in showing degenerative changes of the hard tissues. Imaging should be reserved for patients whose abnormal pain, dysfunction, or both does not respond to conservative short-term treatments such as non-steroidal anti-inflammatory drugs (NSAIDs) and physical therapy. Imaging is also warranted in patients who have a sudden change in the bite or asymmetry of the mandible.
Temporomandibular disorders are divided into articular disorders and muscle disorders. The diagnosis is largely based on the specific system(s) that is affected. However, many patients have both muscle and articular disorders.
The management of TMDs is based on the elimination of pain and the restoration of function and normal activities of daily living. Each specific diagnosis has its own set of management goals based on addressing the problems that affect that patient. Most management plans use conservative, noninvasive treatments; in less than 5% of cases, surgery is used.
The key elements of any conservative management plan are self-care, medication, and physical therapy. Acupuncture is often helpful, as are biofeedback and orthotic splint therapy.
Patients with TMD can be more successfully treated by healthcare practitioners who educate patients about their disorder and involve them in their own treatment. Self-care is an essential part of patient treatment. It should be designed to meet each patient’s treatment objectives. Self-care should be thoroughly explained to patients in language meaningful to them, and it should be reinforced at each visit. This self-care results in better patient compliance and understanding and in better outcomes. The following are 20 self-care tips that have been effective in helping patients manage their TMD:
- The rest of the muscles and joints allow healing.
- Soft food enables muscles and joints to heal.
- Not chewing gum lessens muscle fatigue and joint pain.
- Relax your facial muscles: “Lips relaxed, teeth apart.”
- No clenching; it irritates joints and muscles.
- Yawning against pressure prevents locking open and jaw pain.
- Moist heat for 20 minutes promotes healing and relaxation.
- Ice is for severe pain and new injuries (less than 72 hours).
- Heat and ice—5 seconds of heat, 5 seconds of ice—for pain relief.
- Good posture; avoid head-forward position.
- Sleeping position: side lying, with good pillow support.
- Jaw exercise: open and close against finger pressure.
- Exercise: 20–30 minutes at least 3 times a week.
- Acupressure massage between thumb and forefinger.
- Over-the-counter medications: ibuprofen or aspirin.
- Yoga and meditation for stress reduction.
- Massage promotes healing and relaxation.
- An athletic mouthguard can give temporary relief.
- Avoid long dental appointments.
- Do not cradle the telephone; it aggravates the neck and jaw.
The most common medications for TMD are (1) NSAIDs; (2) muscle relaxants such as cyclobenzaprine; and (3) low doses (10–50 mg) of tricyclic antidepressants such as amitriptyline, desipramine, or nortriptyline. In patients with TMJ synovitis who have a poor response to NSAIDs, a course of an oral steroid such as methylprednisolone (eg, a Depo-Medrol dose pack) for 6 days can be effective. When chronic pain is moderate to severe and does not respond to other treatments, opioid analgesics are often beneficial. Short-acting opioids such as hydrocodone should be avoided in favor of longer-acting codeine or oxycodone. Newer opioids such as tramadol have shown some promise.
Physical therapy has been shown to be helpful for many patients with TMD pain and dysfunction. Heat and ice have beneficial effects on reducing pain in some patients. Jaw exercises can be prescribed for increasing mobility, decreasing hypermobility, strengthening and coordinating muscles, and improving muscle endurance. Massage can be helpful because it promotes increased blood flow through the tissue in addition to inducing muscle relaxation. The evaluation of patient posture is important, and patients should be taught proper posture. A forward-head position can exacerbate neck pain and a tense jaw posture can increase jaw and muscle pain.
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