Temporomandibular joint dysfunction

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,

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 However, these factors are poorly understood, 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,

Classification

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|+ 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, or rheumatological 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. 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.

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. 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).

The three classically described, cardinal signs and symptoms of TMD are: or other types of facial pain including migraine,

Sensation of malocclusion (feeling that the teeth do not meet together properly). In the specialized literature that has evolved around TMD research, arthrosis is differentiated from arthritis by the presence of low and no inflammation respectively. Many suggest that sleep bruxism can be a causative or contributory factor to pain symptoms in TMD. Indeed, the symptoms of TMD overlap with those of bruxism. Others suggest that there is no strong association between TMD and bruxism. A systematic review investigating the possible relationship concluded that when self-reported bruxism is used to diagnose bruxism, there is a positive association with TMD pain, and when more strict diagnostic criteria for bruxism are used, the association with TMD symptoms is much lower. Self-reported bruxism is probably a poor method of identifying bruxism.

Other parafunctional habits such as pen chewing,<!--

Occlusal factors

Occlusal factors as an etiologic factor in TMD is a controversial topic. there are no statistically significant differences in the number of occlusal abnormalities in people with TMD and in people without TMD. A small minority of dentists continue to prescribe occlusal adjustments in the belief that this will prevent or treat TMD despite the existence of systematic reviews of the subject which state that there is no evidence for such practices, and the vast majority of opinion being that no irreversible treatment should be carried out in TMD (see Occlusal adjustment).

Genetic factors

TMD does not obviously run in families like a genetic disease.<!-- The results of one study suggested that the periods of highest pain in TMD can be correlated with rapid periods of change in the circulating estrogen level.<!--

Headache.

Pathophysiology

Anatomy and physiology

Temporomandibular joints

The temporomandibular joints are the dual articulation of the mandible with the skull. Each TMJ is classed as a "ginglymoarthrodial" joint since it is both a ginglymus (hinging joint) and an arthrodial (sliding) joint, and involves the condylar process of the mandible below, and the articular fossa (or glenoid fossa) of the temporal bone above. Between these articular surfaces is the articular disc (or meniscus), which is a biconcave, transversely oval disc composed of dense fibrous connective tissue. Each TMJ is covered by a fibrous capsule. There are tight fibers connecting the mandible to the disc, and loose fibers which connect the disc to the temporal bone, meaning there are in effect 2 joint capsules, creating an upper joint space and a lower joint space, with the articular disc in between.<!-- Due to its concave shape, sometimes the articular disc is described as having an anterior band, intermediate zone and a posterior band. When the mouth is opened, the initial movement of the mandibular condyle is rotational, and this involves mainly the lower joint space, and when the mouth is opened further, the movement of the condyle is translational, involving mainly the upper joint space. This translation movement is achieved by the condylar head sliding down the articular eminence, which constitutes the front border of the articular fossa.

Muscles of mastication

The muscles of mastication are paired on each side and work together to produce the movements of the mandible. The main muscles involved are the masseter, temporalis and medial and lateral pterygoid muscles.

File:Gray383.png|Left medial and lateral pterygoid muscles

File:Gray382.png|Left temporalis muscle

File:Gray378 (masseter highlight).png|Left masseter muscle (red highlight)

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They can be thought of in terms of the directions they move the mandible, with most being involved in more than one type of movement due to the variation in the orientation of muscle fibers within some of these muscles.

Protrusion – Lateral and medial pterygoid.<!--

Each lateral pterygoid muscle is composed of 2 heads, the upper or superior head and the lower or inferior head.<!-- Clicking often accompanies either jaw opening or closing, and usually occurs towards the end of the movement. The noise indicates that the articular disc has suddenly moved to and from a temporarily displaced position (disk displacement with reduction) to allow completion of a phase of movement of the mandible.

Myofascial Pain

Pain originating from the muscles of mastication is thought to be a result of abnormal muscular function or hyperactivity. Some studies have suggested that muscular pain is frequently, but not always, associated with daytime clenching or nocturnal bruxism. Other studies have found that while self-reported nocturnal bruxism was associated with TMD pain, laboratory studies have not found this same magnitude or even the direction of association.

Limitation of mandibular movement

The jaw deviates to the affected side during opening, 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 TMJD therapy can reduce symptoms in the ear, and there is currently an ongoing debate to settle the controversy. ]]

Pain is the most common reason for people with TMD to seek medical advice. This method involves 2 diagnostic axes, namely axis I, the physical diagnosis, and axis II, the psychologic diagnosis.

Assess the integrity of anatomical structures in suspicion of disorders
Staging the extent of any pathology
Monitoring and staging the progress of disease
Determining the effects of treatment

When clinical examination alone is unable to bring sufficient detail to ascertain the state of the TMJ, imaging methods can act as an adjuvant to clinical examination in the diagnosis of TMD. It is reasonable to conclude that plain film can only be used to diagnose extensive lesions. However, the issues lies in the fact that it is impossible to determine whether certain patient groups would benefit more or less from a radiographic examination.

The main indications of CT and CBCT examinations are to assess the bony components of the TMJ, specifically the location and extent of any abnormalities present.

The introduction of cone beam computed tomography (CBCT) imaging allowed a lower radiation dose to patients, in comparison to conventional CT. Hintze et al. compared CBCT and CT techniques and their ability to detect morphological TMJ changes. No significant difference was concluded in terms of their diagnostic accuracy.

Magnetic resonance imaging (MRI)

MRI is the optimal choice for the imaging of soft tissues surrounding the TMJ. It is also useful for assessing the integrity of neural tissues, which may produce orofacial pain when compressed. While having significant diagnostic sensitivity, US has inadequate specificity when identifying osteoarthrosis. Moreover, it is not accurate enough for the diagnosis of cortical and articular disc morphology based on the findings done related to morphological alterations. However, with US, identification of effusion in individuals with inflammatory conditions associated with pain is possible and confirmed by MRI

Management

TMD can be difficult to manage, and since the disorder transcends the boundaries between several health-care disciplines – in particular, dentistry and neurology, the treatment may often involve multiple approaches and be multidisciplinary.

Psychosocial and behavioral interventions

Given the important role that psychosocial factors appear to play in TMD, psychosocial interventions could be viewed to be central to management of the condition.

Hypnosis is suggested by some to be appropriate for TMD. Studies have suggested that it may even be more beneficial than occlusal splint therapy, and has comparable effects to relaxation techniques.

Relaxation techniques include progressive muscle relaxation, yoga, and meditation.

Ear canal inserts are also available, but no published peer-reviewed clinical trials have shown them to be useful.

Medication

Medication is the main method of managing pain in TMD, mostly because there is little if any evidence of the effectiveness of surgical or dental interventions.<!-- or nortriptyline have also been described.

Despite many randomized control trials being conducted on these commonly used medications for TMD a systematic review carried out in 2010 concluded that there was insufficient evidence to support or not to support the use of these drugs in TMD. Examples include morphine, fentanyl, oxycodone, tramadol, hydrocodone, and methadone.

Botulinum toxin solution ("Botox") is sometimes used to treat TMD. Injection of botox into the lateral pterygoid muscle has been investigated in multiple randomized control trials, and there is evidence that it is of benefit in TMD. It is theorized that spasm of lateral pterygoid causes anterior disc displacement. Botulinum toxin causes temporary muscular paralysis by inhibiting acetylcholine release at the neuromuscular junction. There are many different approaches described, but exercises aiming to increase the range of mandibular movements are commonly involved. Jaw exercises aim to directly oppose the negative effects of disuse that may occur in TMD, due to pain discouraging people from moving their jaw. After initial instruction, people are able to perform a physical therapy regimen at home. The most simple method is by regular stretching within pain tolerance, using the thumb and a finger in a "scissor" maneuver. Gentle force is applied until pain of resistance is felt, and then the position is held for several seconds.<!-- "Friction massage" uses surface pressure to cause temporary ischemia and subsequent hyperemia in the muscles, and this is hypothesized to inactivate trigger points and disrupt small fibrous adhesions within the muscle that have formed following surgery or muscular shortening due to restricted movement.

The goals of a PT in reference to treatment of TMD should be to decrease pain, enable muscle relaxation, reduce muscular hyperactivity, and reestablish muscle function and joint mobility. PT treatment is non-invasive and includes self-care management in an environment to create patient responsibility for their own health.

Therapeutic exercise and Manual Therapy (MT) are used to improve strength, coordination and mobility and to reduce pain. Treatment may focus on poor posture, cervical muscle spasms and treatment for referred cervical origin (pain referred from upper levels of the cervical spine) or orofacial pain. MT has been used to restore normal range of motion, promoting circulation, stimulate proprioception, break fibrous adhesions, stimulate synovial fluid production and reduce pain. Exercises and MT are safe and simple interventions that could potentially be beneficial for patients with TMD. No adverse events regarding exercise therapy and manual therapy have been reported.

Occlusal adjustment

This is the adjustment or reorganizing of the existing occlusion, carried out in the belief that this will redistribute forces evenly across the dental arches or achieve a more favorable position of the condyles in the fossae, which is purported to lessen tooth wear, bruxism and TMD, but this is controversial. These techniques are sometimes termed "occlusal rehabilitation" or "occlusal equilibration". The American Society of Maxillofacial Surgeons recommends a conservative/non-surgical approach first. Only 20% of patients need to proceed to surgery.

Examples of surgical procedures that are used in TMD, some more commonly than others, include arthrocentesis,

Alternative medicine

Acupuncture

Acupuncture is sometimes used for TMD. However, some suggest that acupuncture may be no more effective than sham acupuncture, that many of the studies investigating acupuncture and TMD have significant risk of bias,

Chiropractic

Chiropractic adjustments (also termed manipulations or mobilizations) are sometimes used in the belief that this will treat TMD. There is no credible evidence of efficacy in TMD. However, there is some evidence of possible adverse effects from cervical (neck) vertebral manipulation, which sometimes may be serious. It has been suggested that TMD does not cause permanent damage and does not progress to arthritis in later life, An older name for the condition is "Costen's syndrome", eponymously referring to James B. Costen. Costen was an otolaryngologist, Costen hypothesized that malocclusion caused TMD, and placed emphasis on ear symptoms, such as tinnitus, otalgia, impaired hearing, and even dizziness. recommending a treatment revolving around building up the bite. and also because ear problems are now thought to be less associated with TMD. Other historically important terms that were used for TMD include "TMJ disease" or "TMJ syndrome", which are now rarely used.