definition of Wikipedia
|Temporomandibular joint disorder|
|Classification and external resources|
|eMedicine||neuro/366 radio/679 emerg/569|
Temporomandibular joint disorder, TMJD (in the medical literature TMD), or TMJ syndrome, is an umbrella term covering acute or chronic pain, especially in the muscles of mastication and/or inflammation of the temporomandibular joint, which connects the mandible to the skull. The primary cause is muscular hyper- or parafunction, as in the case of bruxism, with secondary effects on the oral musculoskeletal system, like various types of displacement of the disc in the temporomandibular joint. The disorder and resultant dysfunction can result in significant pain, which is the most common TMD symptom, combined with impairment of function. Because the disorder transcends the boundaries between several health-care disciplines — in particular, dentistry and neurology — there are a variety of treatment approaches.
The temporomandibular joint is susceptible to many of the conditions that affect other joints in the body, including ankylosis, arthritis, trauma, dislocations, developmental anomalies, neoplasia and reactive lesions.
Signs and symptoms of temporomandibular joint disorder vary in their presentation and can be very complex, but are often simple. On average the symptoms will involve more than one of the numerous TMJ components: muscles, nerves, tendons, ligaments, bones, connective tissue, and the teeth. Ear pain associated with the swelling of proximal tissue is a symptom of temporomandibular joint disorder.
Symptoms associated with TMJ disorders may be:
Unlike a typical finger or vertebral junctions, each TMJ actually has two joints, which allows it to rotate and to translate (slide). With use, it is common to see wear of both the bone and cartilage components of the joint. Clicking is common, as are popping and deviations in the movements of the joint. Pain is the most conventional signifier of TMD.
The surfaces in contact with one another (cartilage) do not have any receptors to transmit the feeling of pain. The pain therefore originates from one of the surrounding soft tissues, or from the trigeminal nerve itself, which runs through the joint area. When receptors from one of these areas are triggered, the pain can cause a reflex to limit the mandible's movement. Furthermore, inflammation of the joints or damage to the trigeminal nerve can cause constant pain, even without movement of the jaw.
Due to the proximity of the ear to the temporomandibular joint, TMJ pain can often be confused with ear pain. The pain may be referred in around half of all patients and experienced as otalgia (earache). Conversely, TMD is an important possible cause of secondary otalgia. Treatment of TMD may then significantly reduce symptoms of otalgia and tinnitus, as well as atypical facial pain. Despite some of these findings, some researchers question whether TMD therapy can reduce symptoms in the ear, and there is currently an ongoing debate to settle the controversy.
The dysfunction involved is most often in regards to the relationship between the condyle of the mandible and the disc. The sounds produced by this dysfunction are usually described as a "click" or a "pop" when a single sound is heard and as "crepitation" or "crepitus" when there are multiple, rough sounds.
Disorders of the teeth can contribute to TMJ dysfunction. Impaired tooth mobility and tooth loss can be caused by destruction of the supporting bone and by heavy forces being placed on teeth. The movement of the teeth affects how they contact one another when the mouth closes, and the overall relationship between the teeth, muscles, and joints can be altered. Pulpitis, inflammation of the dental pulp, is another symptom that may result from excessive surface erosion. Perhaps the most important factor is the way the teeth meet together: the equilibration of forces of mastication and therefore the displacements of the condyle. Many report TMJ dysfunction after having their wisdom teeth extracted.
There are many external factors that place undue strain on the TMJ. These include but are not limited to the following:
Bruxism has been shown to be a contributory factor in the majority of TMD cases. Over-opening the jaw beyond its range for the individual or unusually aggressive or repetitive sliding of the jaw sideways (laterally) or forward (protrusive). These movements may also be due to parafunctional habits or a malalignment of the jaw or dentition. This may be due to:
Patients with TMD often experience pain such as migraines or headaches, and consider this pain TMJ-related. There is some evidence that some people who use a biofeedback headband to reduce nighttime clenching experience a reduction in TMD. The dentist must ensure a correct diagnosis does not mistake trigeminal neuralgia as a temporomandibular disorder. Oromandibular dystonia is another rare diagnosis which might cause some confusion 
If the occlusal surfaces of the teeth or the supporting structures have been altered due to inappropriate dental treatment, periodontal disease, or trauma, the proper occlusion may need to be restored. Patients with bridges, crowns, or onlays should be checked for bite discrepancies. These discrepancies, if present, may cause a person to make contact with posterior teeth during sideways chewing motions. These inappropriate contacts are called interferences, and if present, they can cause a patient to subconsciously avoid those motions, as they will provoke a painful response. The result can be excessive strain or even spasms of the chewing muscles. Treatment could include adjusting the restorations or replacing them. (Christensen 1997, A Consumer's Guide to Dentistry).
Intra-aural (aural meaning having to do with the ear) device therapy treats TMJ disorder using an appliance worn in the ear canal. The ear canal is in immediate anatomical proximity to the temporomandibular joint (TMJ). "The Clayton Intra-Aural Device (CID) is a hollow, plastic, patented device which rests in the outer third of the ear canal when the jaw is slightly opened." A randomized controlled clinical trial showed the CID to be a non-invasive, safe and effective therapy for the treatment of temporomandibular joint disorder. Based on data submitted to the FDA the CID was given an indication for use "as an aid in reducing temporomandibular disorder (TMD) pain". The CID is sold under the tradename TMDes (ear system).
Occlusal splints (also called night guards or mouth guards) reduce nighttime clenching in some patients, while increasing clenching activity in other patients. Thus, while occlusal splints do prevent loss of tooth enamel from grinding, use of a "one size fits all" splint can worsen TMJ disorder symptoms for some people.
Nighttime EMG biofeedback (for instance by using a biofeedback headband or biofeedback device) can be used to reduce bruxism and thus reduce or eliminate the ongoing nightly cycle of damage that contributes to the majority of TMJ disorder symptoms. This treatment is non-invasive. The Bruxism Association warns that such devices can disrupt sleep and it does not consider them to be a safe treatment.
While conventional analgesic pain killers such as paracetamol (acetaminophen) or NSAIDs provide initial relief for some sufferers, the pain is often more neurologic in nature, which often does not respond well to these drugs.
An alternative approach is for pain modification, for which off-label use of low-doses of Tricyclic antidepressant that have anti-muscarinic properties (e.g. Amitriptyline or the less sedative Nortriptyline) generally prove more effective. In TMJD the muscles are unbalanced. Biofeedback using EMG is successful in balancing these muscles. A mirror can be used as a biofeedback device: Draw a vertical line on mirror. Relax the jaw by relaxing as you exhale. See the jaw relax in the midline. Practice the breathing and relaxing daily using the mirror. When the jaw does open midline the symptoms should abate.
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It is suggested that before the attending dentist commences any plan or approach using medications or surgery, a thorough search for inciting para-functional jaw habits must be performed. Correction of any discrepancies from normal can then be the primary goal.
Patients may employ a nighttime biofeedback instrument such as a biofeedback headband or biofeedback device to help them modify para-functional jaw habits which take place in sleep. In addition, there are various treatment modalities which a well-trained experienced dentist may employ to relieve symptoms and improve joint function. They include:
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An approach to eliminating para-functional habits involves the taking of a detailed history and careful physical examination. The medical history should be designed to reveal duration of illness and symptoms, previous treatment and effects, contributing medical findings, history of facial trauma, and a search for habits that may have produced or enhanced symptoms. Particular attention should be directed in identifying perverse jaw habits, such as clenching or teeth grinding, lip or cheek biting, or positioning of the lower jaw in an edge-to-edge bite. All of the above strain the muscles of mastication (chewing) and result in jaw pain. Palpation of these muscles will cause a painful response.
Treatment is oriented to eliminating oral habits, physical therapy to the masticatory muscles, and alleviating bad posture of the head and neck. A biofeedback headband or biofeedback device may be worn at night to help patients train themselves out of the para-functional habit of nighttime clenching and grinding (bruxism). A flat-plane full-coverage oral appliance, e.g. a non-repositioning stabilization splint, reduces bruxism in some patients, and can take stress off the temporomandibular joint, although some individuals may bite harder on it, resulting in a worsening of their conditions. The anterior splint, with contact at the front teeth only, may prove helpful to some patients, but for those patients who bite harder on this type of splint, even more damage may occur. Thus, different types of splint therapy may work for different patients.
In line with the recommendations of the National Institute of Dental and Craniofacial Research (NIDCR) of the National Institutes of Health (NIH), treatments for TMJD should not permanently alter the jaw or teeth, but need to be reversible. To avoid permanent change, over-the-counter or prescription pain medications may be prescribed. Some sufferers may also benefit from gentle stretching or relaxation exercises for the jaw, which may be recommended by their healthcare providers.
Other interventions include:
Attempts in the last decade to develop surgical treatments based on MRI and CAT scans now receive less attention. These techniques are reserved for the most difficult cases where other therapeutic modalities have failed. Exercise protocols, habit control, and splinting should be the first line of approach, leaving oral surgery as a last resort. Other possible causes of facial pain and jaw immobility and dysfunction should be the initial consideration of the examining professional.
One option for oral surgery is to manipulate the jaw under general anaesthetic and wash out the joint with a saline and anti-inflammatory solution in a procedure known as arthrocentesis. In some cases, this will reduce the inflammatory process.
The jaw can dislocate if a person opens their mouth too wide, particularly when a person attempts to open the jaw widely in an effort to stretch the facial muscles i.e. to relieve tense facial muscles as the wisdom teeth develop and emerge.
The jaw can also "slide out" as the person is sleeping on their side.
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