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.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.
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). Classification
TMD is considered by some to be one of the 4 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. Others consider TMD a "central sensitivity syndrome", in reference to evidence that TMD might be caused by a centrally mediated sensitivity to pain. 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. These disorders have also been theorized to be caused by centrally mediated sensitivity to pain, and furthermore they often occur together. 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.