Temporomandibular Disorders: Review and Management

US Pharm. 2007;32(12):HS-18-HS-26.

Temporomandibular disorders (TMDs) are the most common type of facial pain condition, affecting approximately 10% to 12% of the population, with about 25% of individuals having at least one TMD episode during their lifetime.¹

TMDs, which fall under the category of musculoskeletal disorders, is a collective term used to describe a number of related conditions affecting the temporomandibular joint (TMJ) and/or masticatory muscles, all of which have three common symptoms: orofacial pain, joint noises, and restricted jaw opening during jaw movements such as speaking or chewing.² Patients have reported symptoms ranging from mild (i.e., not requiring treatment) to moderate or severe (i.e., requiring treatment). In actuality, only about 5% to 6% of patients need treatment, with women seeking treatment more often than men. Treatment of TMDs is challenging and controversial in the medical and dental fields.³

Anatomy
The TMJ is a synovial joint located at the junction of the mandible (lower jaw) and the temporal bone of the skull (immediately in front of the ear on each side of the head). A small cushioning disk of cartilage separates the bones, similar to that in the knee joint, so that the mandible can slide easily. The TMJ moves upon chewing, yawning, talking, and swallowing. It is easily located by placing a finger on the triangular structure in front of the ear. The TMJ can be felt in function by moving the finger slightly forward and pressing firmly while opening the jaw to the maximum separation of the teeth and then shutting it.

Classification of TMDs
Many terms have been used to describe TMDs, including TMJ syndrome and TMJ disease; however, the term TMD is the preferred term used by the American Academy of Orofacial Pain (AAOP) and other professionals. Various classifications and clinical diagnostic criteria exist to describe TMD.

The AAOP defines two classifications of TMDs: muscle-related, or myogenic, TMD and joint related, or arthrogenous, TMD.⁴ Occasionally, both types may be present simultaneously, making a diagnosis difficult. Myogenic TMD, the more common form, only involves functional alterations of the masticatory muscles around the TMJ without TMJ problems. It usually occurs in persons with high stress and is caused by nocturnal bruxism (teeth grinding) or day- or nighttime teeth clenching. Arthrogenous TMD may be caused by disk displacement, recurrent dislocation, degenerative joint disorders, hypermobility of the joint, osteoarthritis, ankylosis, or neoplasia. Temporomandibular dysfunction occurs when there is a displacement of the cartilaginous disk, causing pressure and stretching of the associated muscles and sensory nerves. The characteristic "clicking" or "popping" occurs when the mandible moves and the disk snaps into place. Pain is also associated with spasm of the chewing muscles (i.e., masseter, temporalis, and pterygoid).

In the past, there was no reliable and valid method of diagnosing TMD patients, which led to serious misclassification of TMD cases. However, in 1992, clinical research experts (with support from the National Institute of Dental and Craniofacial Research) developed and published "Research Diagnostic Criteria for Temporomandibular Disorders," which established specific operational examination procedures and diagnostic criteria that are used in epidemiologic and clinical research for defining TMD.⁵ These criteria describe a diagnosis along two separate axes: the Axis I score provides a clinical diagnosis, while the Axis II score provides an assessment of the psychological/behavioral aspects.

Etiology

There are many causes, both specific and nonspecific, of TMJ pain and dysfunction, which continue to be controversial. One reason for this controversy is that some factors are risk factors, while others are causal in nature or purely coincidental to the TMD problem.^6,7 Although the etiologies are poorly understood, most clinicians and researchers suggest a multifactorial etiology for TMD involving physical, psychological, and social factors.

Physical Factors: Sustained or repetitive loading of the masticatory system, which occurs during parafunctional jaw activities--such as bruxism; teeth clenching; pencil or pen chewing; gum chewing; lip biting; sucking on lips, fingers, and cheek; and nail biting--can result in muscle hyperactivity and overloading of the TMJ. ⁸ Bruxism occurs in approximately 6% to 20% of the population and between 67% and 87.5% of patients with TMD.⁹ Using caffeine, tobacco, or cocaine may increase the risk of bruxism.

Trauma to the joint can occur after a physical blow to the area or as a result of head or neck injury. Prolonged opening of the mouth during a dental appointment (e.g., third molar extractions),¹⁰ yawning, eating, or even excessive gum chewing can cause trauma to the TMJ and related muscles.

Behavioral Factors: Psychological factors that are seen in TMD patients include stress, anxiety, and depression.¹¹ A recent article suggested that with appropriate early biopsychosocial intervention, acute TMD patients can be effectively treated, regardless of the presence or absence of vulnerability to depression symptomatology.¹²

Clinical Signs and Symptoms
In patients with TMD, orofacial pain may be dull or sharp and occurs when the patient swallows, talks, or chews. Often, the pain originates in the periauricular area; however, it may radiate to other locations. If the joint is not properly aligned or not working correctly, the smooth cartilage that allows the joint to move easily may wear down, resulting in a popping or clicking noise when the jaw opens and closes. Crepitus, a crackling or crushing noise, occurs in more severe cases. The patient often has limited jaw-opening ability. There may be tenderness to palpation of the TMJ via the external auditory meatus. The adjacent muscles of the face and jaws are often in spasm, with pain and tenderness felt in the temple area, cheek, mandible, and teeth. Patients with TMD have similar symptoms to those of patients with other chronic pain conditions, such as headache, toothache, earache, tinnitus, neck pain, and other types of facial pain.¹³

Clinical Evaluation and Diagnosis
Due to the multifactorial nature of TMD, establishing a diagnosis of is difficult. Although TMDs are a chief source of chronic orofacial pain, other etiologies must be considered, including neoplasm, aneurysm, migraine, sinus problems, tooth pathology (e.g., impacted wisdom tooth), nerve damage, and vascular arteritis.

Clinical examination of the patient involves evaluation of the range of mandibular movement by recording the maximum mouth opening (from lower to upper front teeth) using a ruler or caliper. If the measurement is less than 40 mm or if less than three fingers fit in the mouth, then the patient has a decreased range of motion, which is usually accompanied by pain and discomfort. Additionally, bilateral auscultation of TMJ noises and gentle digital palpation of the joints and masticatory muscles (i.e., temporalis anterior, masseter, pterygoideus internus) should be performed.¹⁴ Any tenderness or pain in the joints and/or muscles and joint noises (i.e., clicking or crepitus when the patient opens and closes the mouth) should be recorded.

Magnetic resonance imaging (MRI) or computed tomography (CT) scan of the TMJ and orofacial structures may be performed to rule out other conditions, such as arthritis or a tumor.¹⁵ However, radiographs are sometimes difficult to interpret.

A dental examination should be performed to detect any teeth malocclusion (e.g., crossbite). A complete patient history should include a review of any oral habits (e.g., bruxism, clenching, nail biting). Evaluation of the occlusal (top) surface of teeth will determine if the patient has occlusal wear indicative of bruxism or clenching.

In patients with chronic TMD, behavioral, social, and emotional assessments should be performed.

Treatment
Many individuals undergo various expensive and unproven treatments that may not be effective. TMDs are often self-limiting and do not progress. However, in some patients the TMJ undergoes continued degeneration, with a worsening of symptoms. Since the primary focus of pain is around the ear, the individual may first visit an ear, nose, and throat physician or otolaryngologist. Having eliminated the possibility of headache, ear, or sinus problems, the next step is to consider the possibility of TMJ pain and dysfunction. The dentist should be the next health care provider that the individual seeks.

Management of TMJ dysfunction may involve the use of medications or other nonsurgical or surgical options ( TABLE 1).

Pharmacotherapy: In patients presenting with acute joint and muscle pain for less than three months, treatment should be aimed at a reduction of inflammation and pain using nonsteroidal anti-inflammatory drugs (NSAIDs)† and muscle relaxants. ³ Due to the ulcergoenic potential of NSAIDs, however, not all patients are good candidates. Patients presenting with chronic pain, along with anxiety or depression, may require antidepressants or anxiolytics.

Nonsteroidal anti-inflammatory agents are the first line of treatment to reduce inflammation and pain. Duration of therapy should be about two to four weeks. Benzodiazepines are prescribed for significant muscle pain or spasm. Tricyclic antidepressants in low dosages may reduce pain and nighttime bruxism. However, there have been reports that antidepressants may trigger bruxism in nonbruxers.¹⁶

One of the newest treatment options for TMJ-induced muscle spasms is injection of botulinum toxin.¹⁷ Botulinum toxin is a neurotoxic protein produced by the bacterium Clostridium botulinum. When botulinum toxin A (Botox) is injected in minute doses (15 units) into the affected muscles around the TMJ, acetylcholine released from nerve terminals is inhibited, thus blocking neuromuscular transmission and rendering the muscle unable to contract. It takes about 24 to 72 hours after an injection for clinical effects to be seen. Unfortunately, this amelioration usually lasts for only three to four months, so most patients require repeated injections over many years. Long-term effects of this therapy have not been studied.

Behavioral Therapy: Reduction in stress, anxiety, and depression using behavioral modification (e.g., relaxation therapy, hypnosis, biofeedback, meditation) and counseling is an important part of treatment.

Occlusal Therapy: The primary concern is to rest the muscles and joints. Individuals are informed to eat soft foods and not to chew gum. To help reduce the incidence of bruxism and clenching, the dentist may fabricate a soft or hard acrylic bite plate (also referred to as an occlusal guard, night guard, or orthopedic appliance) that is placed on the maxillary (upper) teeth.¹⁸ This appliance is worn at night and helps prevent the teeth from occluding, thus resting on the joint and reducing wear and tear.

Surgical Therapy: Arthroscopic surgery may be effective in improving the range of mandibular movement and pain reduction, but it is mainly performed in patients with severe joint problems.

Arthrocentesis is a surgical procedure that washes the upper compartment of the TMJ using saline injections into the joint space. The fluid is then withdrawn and a second injection lavages the joint. Corticosteroids can then be injected into the joint space.

Home Care: At home, patients should apply moist heat to the affected area at least twice a day for no longer than 15 minutes. The various masticatory muscles involved should be massaged several times a day until the muscle is not painful to touch.

Other Treatments: Ultrasonic treatment uses waves that penetrate deeper into the tissue, increasing blood flow and reducing pain. This procedure should be done on alternate days for about 10 minutes. Acupuncture and electronic muscle stimulation are other methods of treatment.

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