Temporomandibular disorders

What are temporomandibular disorders?

Temporomandibular disorders (TMDs) are a group of conditions affecting the temporomandibular joint (TMJ), masticatory muscles, and associated structures. These disorders are characterised by shared symptoms, including TMJ pain, tenderness of the masticatory muscles, headache, limited mouth opening, and joint noises (eg, clicking, popping, or crepitus).¹

TMDs (previously referred to as TMJ disorders or TMJ dysfunction) are the most common cause of chronic orofacial pain.

Pain-related TMDs can be subdivided into several categories:¹

• Myalgia/myofascial pain: masticatory muscle disorders.

• TMJ disorders: include disc displacement (commonly resulting from an abnormal relationship or misalignment of the articular disc of the TMJ relative to the condyle) or arthralgia, which may result from localised degeneration of the TMJ.

• Headache: typically localised to the temporal region.

TMDs may also be classified based on the duration of symptoms. Acute TMD pain is typically of short duration, self-limiting, and often associated with prolonged jaw opening, such as following dental treatment or trauma. Chronic TMD pain, on the other hand, is defined as pain persisting for more than three months.¹

How common are temporomandibular disorders? (Epidemiology)²

TMJ symptoms are relatively common, although only about 5% seek medical help for their symptoms. TMDs can occur at any age but peak during the second and third decades of life. They are more common in women.¹

A systematic review conducted in 2021 reported that the prevalence of TMDs in the general population was approximately 31% in adults and 11% in children.³

Temporomandibular symptoms are commonly found in musicians, particularly wind and string players.⁴

There is also an increase in symptoms among patients with schizophrenia.⁵ This is likely due to a number of factors including poor oral health and psychological factors as well as use of antipsychotic medication.

Aetiology¹⁶

TMDs are believed to have a multifactorial aetiology, although the pathophysiology is not well understood. The causes are likely complex and varied, potentially including anatomical factors, such as internal derangement of the TMJ caused by disc displacement.

• Macrotrauma - for example, following a dental procedure or a fall onto the chin.

• Microtrauma - parafunctional habits (eg, nail biting, tongue thrusting) can overload the TMJ, leading to cartilage breakdown and alterations in the synovial fluid. Bruxism (grinding or clenching of teeth) is often considered a parafunctional habit.

• Psychosocial factors - such as stress, anxiety, and depression may lead to the development and chronification of TMDs.

• There may be an association between TMDs and other chronic pain conditions including chronic fatigue syndrome, fibromyalgia, migraine, irritable bowel syndrome, and widespread chronic pain.

• Genetic risk factors have also been identified in TMDs.⁷

Factors affecting muscles and joint function - myofascial pain and dysfunction

This type of TMJ problem is most common. While it is often difficult to identify a single cause, contributing factors may include:

• Chronic pain syndromes or increased pain sensitivity.

• Psychological factors: these may contribute, as with other chronic pain syndromes.

• Muscle overactivity: bruxism and orofacial dystonias.

• Dental malocclusion was once considered an important factor in the development of TMJ dysfunction, with the condition often regarded as a dental problem. However, current evidence does not support this view, and TMJ dysfunction is now recognised as a multifactorial condition rather than solely a dental issue.

Factors affecting the joint

The most common problems are:

• Intra-articular disc derangement (various types).

• Osteoarthritis.

• Rheumatoid arthritis.

Other problems affecting the joint are:

• Other types of arthropathy - eg, gout, pseudogout or spondyloarthropathy.

• Trauma.

• TMJ hypermobility or hypomobility.

• Infection.

• Congenital disorders - eg, branchial arch disorder.

• Tumours (rare).

Assessment of temporomandibular disorders

Diagnosis is based on the history and physical examination. The assessment of patients suspected of having TMD should follow a biopsychosocial approach. It should assess the impact of symptoms on the individual's quality of life, identify associated comorbid conditions, and consider psychological factors contributing to the symptoms.

Risk factors include age (20–40 years), female sex, pain-related comorbidities, anxiety and depression.

Symptoms of temporomandibular disorders

TMDs typically present with pain in the TMJ and surrounding structures, limitations in jaw movement, and/or sounds such as clicking, popping, grating, or crepitus originating from the TMJ. ¹

Pain

• Located in and around the TMJ and/or masticatory muscles which may radiate to the head, neck and ear.

• Pain, located immediately in front of the tragus of the ear, projecting to the ear, temple, cheek and along the mandible, is highly diagnostic for TMD.

• If pain is not related to using the jaw, it is unlikely to be due to TMD.

Restricted jaw motion

• May affect mandibular movement in any direction.

• Jaw movements increase the pain.

• Patients may report a generalised tight feeling, likely indicative of a muscular disorder, or a sensation of the jaw 'catching' or 'getting stuck', which is typically associated with internal derangement of the joint.

Joint noise

• Patients with myofascial pain may have palpable or audible joint clicks during jaw movement, while those with internal derangement have clicking and possible locking and restricted jaw opening.

• Joint noise without associated functional problems or pain is considered a normal anatomical variation and may occur in up to 50% of the population. Joint noise is significant when accompanied by other symptoms.

Other symptoms may include:

• Ear symptoms - otalgia, tinnitus, dizziness.

• Headache.

• Neck pain.

• 'Locking' episodes - refer to the inability to open or close the mouth, with difficulty opening being more common.

TMDs may also cause:¹

• Chronic pain.

• Psychosocial distress.

• Dental problems.

• Speech problems.

• Swallowing and chewing difficulties.

Examination⁸

• Palpate the joint by placing the fingertips in the preauricular region just in front of the tragus of the ear. The patient is then asked to open their mouth and the fingertip will fall into the depression left by the translating condyle.

• Palpate the head, neck and masticatory muscles for areas of tenderness, trigger points or hypertrophy. Examine the muscles of mastication with the teeth clenched.

• Joint clicks or grating sounds during jaw movement may be palpable or audible with a stethoscope placed over the preauricular area.

• Assess mandibular movement:

  • Measure the distance of painless vertical mouth opening, using inter-incisal distance (normal range 35-55 mm).

  • Observe the line of the vertical jaw opening: straight or deviating, smooth or jerky.

  • Examine lateral movements and jaw protrusion.

• Assess other orofacial structures - salivary glands, oral cavity, dentition, ears and cranial nerves.

Differential diagnosis⁹

• Giant cell arteritis.

• Cardiac pain (angina and acute coronary syndromes) can radiate to the neck and jaw but is usually more acute.

• Dental problems - a dental check-up may be necessary, particularly if this is the first presentation.

• Trigeminal neuralgia.

• Migraine and other causes of headache.

• Herpes zoster.

• Other ENT disorders - eg, salivary gland disorders and ENT neoplasms.

The location of the pain helps in diagnosis. The pain in TMDs is centred immediately in front of the tragus of the ear and projects to the ear, temple and cheek and along the mandible.

'Red flags' for orofacial pain that may mimic TMDs include:¹

• Previous history of malignancy (possible new primary, recurrence, or metastases).

• Persistent or unexplained neck lump or cervical lymphadenopathy (neoplastic, infective, or autoimmune cause).

• Neurological symptoms - eg, headache, cranial nerve abnormalities with sensory or motor function changes (intracranial cause, or malignancy affecting cranial nerve peripheral branches).

• Facial asymmetry, facial mass or swelling, or profound trismus (neoplastic, infective, or inflammatory cause).

• Recurrent epistaxis, purulent nasal discharge, persistent loss of smell, or reduced hearing on the same side (nasopharyngeal carcinoma).

• Unexplained fever or weight loss (malignancy, immunosuppression, or an infection).

• New-onset unilateral headache or scalp tenderness, jaw claudication, and general malaise, especially if the person is over 50 years of age (giant cell arteritis).

• Occlusal (bite) changes from neoplasia, rheumatoid arthritis, trauma, or bone growth around the temporomandibular joint, for example in conditions such as acromegaly.

Treatment for temporomandibular disorders^11011121314

Primary care

Early self-management to help control symptoms and limit functional impairment:

• Reassure that the condition is usually non-progressive, and that symptoms may fluctuate, but should improve.

• Eat a soft diet and rest the jaw if there is acute pain.

• Try to avoid parafunctional activities that may exacerbate symptoms - eg, wide yawning, teeth grinding or jaw clenching, chewing gum or pencils, and nail biting.

• Take simple analgesia such as paracetamol or NSAIDs.

• Apply local measures for pain relief, such as using covered ice, a warm flannel, or a heat pad, or by massaging the affected muscles.

• Identify sources of stress, and try relaxation techniques.

• Advice on sleep hygiene.

• Provide sources of information and advice.

Consider additional drug treatment for adults:

• If symptoms are acute and severe, consider a short course of a low-dose benzodiazepine for a maximum of two weeks.

• If there is chronic pain, consider a neuropathic analgesic such as amitriptyline or gabapentin.

Referral

Refer to oral medicine or oral and maxillofacial surgery if:

• There is history of trauma or fracture.

• There is markedly limited mouth opening (closed lock) suggesting disc displacement without reduction.

Consider referral to additional specialists if appropriate including:

• A dentist, if there is poor dental health, suspected malocclusion or dental pathology, or for consideration of an occlusal splint (usually worn at night and which may be useful for people who grind or clench their teeth).

• Psychology services for cognitive behavioural therapy (CBT), if there is marked psychological distress or to help with pain-related anxiety.

• Physiotherapy for advice on passive jaw stretching exercises, posture training, and massage, or acupuncture to help relax muscle spasm.

Arrange referral to oral medicine; oral and maxillofacial surgery; ENT surgery; neurology; or a multidisciplinary pain clinic for specialist investigations and management, depending on clinical judgement, if a person has:

• Chronic TMD symptoms lasting for more than three months.

• Persistent or worsening symptoms despite primary care treatment.

• Uncertain diagnosis.

• Marked psychological distress associated with symptoms and/or occlusal preoccupation (persistent hyper-awareness or hypervigilance of their bite).

• Unexplained persistent pain or chronic widespread pain.

Specialist investigations and management

Specialist investigations may include:

• Plain or panoramic X-rays to identify dental pathology, fractures, dislocations, or severe degenerative joint disease.

• CT to assess for degenerative joint disease or subluxation of the TMJ.

• MRI to assess for TMJ disc displacement, subluxation, arthrosis, or synovial proliferation.

Specialist management options include:

• Botulinum toxin injection into the masseter and temporalis muscles of mastication.

• Intra-articular injection of sodium hyaluronate or corticosteroid preparations for degenerative joint disease.

• Surgery options:

  • Arthrocentesis or arthroscopy for non-myogenous TMDs with significant functional impairment.

  • Arthroplasty for more severe TMJ degeneration.

  • Eminectomy or eminoplasty for recurrent TMJ dislocation.

  • Total prosthetic TMJ replacement for end-stage degenerative disease.¹⁵

Neither occlusal adjustment (selective grinding of the tooth enamel to achieve a more harmonious bite) nor orthodontics are recommended, because of a lack of evidence of benefit.

Prognosis¹

TMDs are usually self-limiting. Symptoms resolve spontaneously in up to 40% of people, and 50-90% of symptoms improve with conservative treatment.

TMDs share many features with other functional and complex pain syndromes, and their prognosis depends on both psychological and mechanical factors. A multidisciplinary approach to treatment often leads to favourable outcomes.

Factors associated with chronic TMD pain and a worse prognosis include:

• Being female.

• Increasing age at presentation.

• Higher reported pain intensity.

• More widespread nonspecific symptoms.

• Comorbid psychosocial factors - eg, anxiety or depression.