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
+ Classification (Expanded DC/TMD taxonomy):Temporomandibular Joint Disorders Joint pain Arthralgia Arthritis Joint disorders Disc disorders Disc displacement with reduction Disc displacement with reduction with intermittent locking Disc displacement without reduction with limited opening Disc displacement without reduction without limited opening Hypomobility disorders other than disc disorders Adhesions/Adherence Ankylosis Fibrous Osseous Hypermobility disorders Dislocations Subluxation Luxation Joint diseases Degenerative joint disease Osteoarthrosis Osteoarthritis Systemic arthritides Condylysis/Idiopathic condylar resorption Osteochondritis dissecans Osteonecrosis Neoplasm Synovial Chondromatosis Fractures Congenital/developmental disorders Aplasia Hypoplasia Hyperplasia
Masticatory Muscle Disorders
Muscle pain Myalgia Local myalgia Myofascial pain Myofascial pain with referral Tendonitis Myositis Spasm Contracture Hypertrophy Neoplasm Movement Disorders Orofacial dyskinesia Oromandibular dystonia Masticatory muscle pain attributed to systemic/central pain disorders Fibromyalgia/widespread pain
Headache
Headache attributed to TMD
Associated Structures
Coronoid hyperplasia 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:
By cause and symptoms Some classification systems distinguish muscle-related (myogenous) TMD (also termed myogenous TMD, or TMD secondary to myofascial pain and dysfunction) from joint-related TMD (also termed arthogenous TMD, or TMD secondary to true articular disease), based upon whether the muscles of mastication or the TMJs themselves are predominantly involved. This classification, which effectively divides TMD into 2 syndromes, is followed by the American Academy of Orofacial Pain. However, since most people with TMD could be placed into both of these groups, it makes a single diagnosis difficult when this classification is used. The Diagnostic Criteria (DC/TMD) allows for multiple diagnoses in an attempt to overcome the problems with other classifications. DC/TMD considers temporomandibular disorders in 2 axes; axis I is the physical aspects, and axis II involves assessment of psychological status, mandibular function and TMD-related psychosocial disability. Axis I is divided into 5 general groups of disorders and allows for diagnoses from each group for each joint. These include the muscle pain, joint pain, disc displacement, degenerative joint disorder, and subluxation disorder diagnoses. Axis II assessments allows clinicians to evaluate the impact of TMD on quality of life in the process of diagnosis, and treatment planning.
It has been suggested that TMD may develop following physical trauma, particularly whiplash injury, although the evidence for this is not conclusive. This type of TMD is sometimes termed "posttraumatic TMD" (pTMD) to distinguish it from TMD of unknown cause, sometimes termed "idiopathic TMD" (iTMD).
By duration Sometimes distinction is made between acute TMD, where symptoms last for less than three months, and chronic TMD, where symptoms last for more than three months. Not much is known about acute TMD since these individuals do not typically attend in secondary care (hospital).
Signs and symptoms Signs and symptoms of temporomandibular joint disorder vary in their presentation. The symptoms will usually involve more than one of the various components of the masticatory system, muscles, nerves, tendons, ligaments, bones, connective tissue, or the teeth.
The three classically described, cardinal signs and symptoms of TMD are: Pain and tenderness on palpation in the muscles of mastication, or of the joint itself (preauricular pain – pain felt just in front of the ear). Pain is the defining feature of TMD and is usually aggravated by manipulation or function, such as when chewing, clenching, or yawning, and is often worse upon waking. The character of the pain is usually dull or aching, poorly localized, and intermittent, although it can sometimes be constant. The pain is more usually unilateral (located on one side) rather than bilateral. It is rarely severe. Limited range of mandibular movement, which may cause difficulty eating or even talking. There may be locking of the jaw, or stiffness in the jaw muscles and the joints, especially present upon waking. There may also be incoordination, asymmetry or deviation of mandibular movement. Noises from the joint during mandibular movement, which may be intermittent. Joint noises may be described as clicking, popping, or crepitus (grating).
TMJ dysfunction is commonly associated with symptoms affecting cervical spine dysfunction and altered head and cervical spine posture.
Other signs and symptoms have also been described, although these are less common and less significant than the cardinal signs and symptoms listed above. Examples include: Headache (possibly), e.g. pain in the occipital region (the back of the head), or the forehead; or other types of facial pain including migraine, tension headache, or myofascial pain. Pain elsewhere, such as the teeth or neck. Diminished auditory acuity (hearing loss). Tinnitus (occasionally). Dizziness. Sensation of malocclusion (feeling that the teeth do not meet together properly).
Causes TMD is a symptom complex (i.e. a group of symptoms occurring together and characterizing a particular disease), which is thought to be caused by multiple, poorly understood factors, but the exact etiology is unknown. There are factors which appear to predispose to TMD (genetic, hormonal, anatomical), factors which may precipitate it (trauma, occlusal changes, parafunction), and also factors which may prolong it (stress and again parafunction). Overall, two hypotheses have dominated research into the causes of TMD, namely a psychosocial model and a theory of occlusal dysharmony. Interest in occlusal factors as a causative factor in TMD was especially widespread in the past, and the theory has since fallen out of favor and become controversial due to lack of evidence.
Disc displacement