Temporomandibular joint dysfunction (TMD, TMJD) is a spectrum of disorders relating to pain and dysfunction of the muscles of mastication (the muscles that move the jaw) and the temporomandibular joints (the joints which connect the mandible to the skull). The major common presenting symptoms are pain, alterations in the range of mandibular movement, and/or noises from the temporomandibular joints (TMJ) during function. Although TMD is not life-threatening, it can be detrimental to quality of life, especially in the form of chronic pain. In this article, the term temporomandibular disorder (TMD) is taken to mean any disorder that affects the temporomandibular joint or masticatory muscles, and temporomandibular joint disorder (TMJD, but sometimes TMJD) is taken to mean dysfunction of the temporomandibular joint. However, there is no single, globally accepted term or definition concerning this topic. TMDs have a range of causes and often co-occur with a number of overlapping medical conditions, including headaches, fibromyalgia, back pain, and irritable bowel. However, these factors are poorly understood, and there is disagreement as to their relative importance. There are many treatments available, although there is a general lack of evidence for any treatment in TMD, and no widely accepted treatment protocol. Common treatments include provision of occlusal splints, psychosocial interventions like cognitive behavioral therapy, physical therapy, and pain medication or others. Most sources agree that irreversible treatment should generally be avoided. The prevalence of TMD in the global population is 34%. It varies by continent: the highest rate is in South America at 47%, followed by Asia at 33%, Europe at 29%, and North America at 26%. About 20% to 30% of the adult population are affected to some degree. Usually people affected by TMD are between 20 and 40 years of age, and it is more common in females than males. TMD is the second most frequent cause of orofacial pain after dental pain (i.e. toothache). By 2050, the global prevalence of TMD may approach 44%.
Classification
TMD is considered by some to be one of the four major symptom complexes in chronic orofacial pain, along with burning mouth syndrome, atypical facial pain and atypical odontalgia. TMD has been considered as a type of musculoskeletal, neuromuscular, or rheumatological disorder. It has also been called a functional pain syndrome, and a psychogenic disorder. It is hypothesized that there is a great deal of similarity between TMD and other pain syndromes like fibromyalgia, irritable bowel syndrome, interstitial cystitis, headache, chronic lower back pain and chronic neck pain.
Definitions and terminology Frequently, TMD has been treated as a single syndrome, but the prevailing modern view is that TMD is a cluster of related disorders with many common features. Indeed, some have suggested that, in the future, the term 'TMD' may be discarded as the different causes are fully identified and separated into different conditions. Sometimes, "temporomandibular joint dysfunction" is described as the most common form of temporomandibular disorder, whereas many other sources use the term 'temporomandibular disorder' synonymously, or instead of the term 'temporomandibular joint dysfunction'. In turn, the term 'temporomandibular disorder' is defined as "musculoskeletal disorders affecting the temporomandibular joints and their associated musculature. It is a collective term which represents a diverse group of pathologies involving the temporomandibular joint, the muscles of mastication, or both". Another definition of temporomandibular disorders is "a group of conditions with similar signs and symptoms that affect the temporomandibular joints, the muscles of mastication, or both." 'Temporomandibular disorder' is a term that creates confusion since it refers to a group of similarly symptomatic conditions, whilst many sources use the term temporomandibular disorders as a vague description, rather than a specific syndrome, and refer to any condition which may affect the temporomandibular joints (see table). The temporomandibular joint is susceptible to a huge range of diseases, some rarer than others, and there is no implication that all of these will cause any symptoms or limitation in function at all. Only 33% of those with signs of TMD will have symptoms. The preferred terms in medical publications is to an extent influenced by geographic location. For example, in the United Kingdom, the term 'pain dysfunction syndrome' is in common use. In the United States, the term 'temporomandibular disorder' is generally favored. The American Academy of Orofacial Pain uses 'temporomandibular disorder', whilst the National Institute of Dental and Craniofacial Research uses 'temporomandibular joint disorder'. A more complete list of synonyms for this topic is extensive, with some being more commonly used than others. In addition to those already mentioned, examples include 'temporomandibular joint pain dysfunction syndrome', 'temporomandibular pain dysfunction syndrome', 'temporomandibular joint syndrome', 'temporomandibular dysfunction syndrome', 'temporomandibular dysfunction', 'temporomandibular disorder', 'temporomandibular syndrome', 'facial arthromyalgia', 'myofacial pain dysfunction syndrome', 'craniomandibular dysfunction' (CMD), 'myofacial pain dysfunction', 'masticatory myalgia', 'mandibular dysfunction', and 'Costen's syndrome'. The lack of standardization in terms is not restricted to medical papers. Notable internationally recognized sources vary in both their preferred term, and their offered definition. For example:
"Temporomandibular Pain and Dysfunction Syndrome – Aching in the muscles of mastication, sometimes with an occasional brief severe pain on chewing, often associated with restricted jaw movement and clicking or popping sounds." (Classification of Chronic Pain, International Association for the Study of Pain). "Headache or facial pain attributed to temporomandibular joint disorder." (International Classification of Headache Disorders 2nd edition (ICHD-2), International Headache Society). "Temporomandibular joint-pain-dysfunction syndrome" listed in turn under "Temporomandibular joint disorders" (International Classification of Diseases 10th revision, World Health Organization).
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