Temporomandibular Dysfunction (TMD)

TMD encompasses a group of disorders affecting the masticatory system, including muscular conditions and those affecting the temporomandibular joint (TMJ).

Prevalence

• Signs of TMD appear in 60-70% of the population.
• Peak incidence: adults aged 20-40 years.
• Women are at least four times as likely to suffer from TMD.
• Symptomatic disease requiring treatment: 5-12% of the population.

Common Symptoms

• Pain involving the TMJ and surrounding structures.
• Joint dysfunction.

Anatomy

TMJ Structure

• Ginglymoarthrodial joint formed by the mandibular condyle and the glenoid fossa of the temporal bone.
• Composed of two joints separated by an articular disc.
• Most frequently used joint in the body, allowing movements for mastication, swallowing, and communication.

Musculature

• Primary muscles of mastication: masseter, temporalis, medial and lateral pterygoid muscles.

Innervation

• Sensory innervation by branches of the third division of the trigeminal nerve (auriculotemporal and masseteric nerves).
• Auriculotemporal nerve also innervates the temporal region, external ear, and tympanic membrane, highly sensitive to pain.

Aetiology

General Factors

• Multifactorial, including anatomical, pathophysiological, and psychosocial factors.
• Distinction between myofascial causes and intra-articular disorders is crucial.

Myofascial Disorders

• Caused by tension, fatigue, or spasm of masticatory muscles.
• Contributing factors: bruxism, teeth grinding, clenching, abnormal posture, stress, and anxiety.
• Associated with cognitive and psychiatric disturbances, autoimmune disorders, fibromyalgia, and other chronic pain conditions.

Intra-articular Causes

• Include internal joint derangement, osteoarthritis, capsular inflammation, hypermobility, and traumatic injury.
• Inflammatory conditions like rheumatoid arthritis and ankylosing spondylitis can lead to joint derangement.
• Most common intra-articular cause: articular disc displacement (though often asymptomatic in the general population).

Other Considerations

• Minimal evidence linking occlusion abnormalities to TMD.

Causes of Orofacial Pain

Dental Conditions

• Caries
• Tooth abscess
• Tooth eruption

Otological Conditions

• Acute otitis media
• Otitis externa (acute or malignant)
• Mastoiditis
• Eustachian tube dysfunction

Headache Disorders

• Tension-type headache
• Migraine
• Cluster headache

Neurogenic Conditions

• Trigeminal neuralgia
• Postherpetic neuralgia
• Glossopharyngeal neuralgia

Inflammatory Conditions

• Temporal arteritis
• Rheumatoid arthritis
• Systemic lupus erythematosus
• Parotitis

Traumatic

• Mandibular fracture/dislocation
• Temporal bone fracture

Other

• Atypical facial pain
• Sinusitis
• Eagle syndrome (stylohyoid syndrome)

Clinical Assessment

History

Pain Characteristics

• Site, onset, character of pain, radiation, duration, and associated symptoms.
• Typically described as pain within the TMJ or mandible.
• May refer to the scalp or neck.
• Often exacerbated by mastication, yawning, or extended talking.

Common Symptoms

• Difficulty opening the mouth.
• Clicking, popping, or crepitus within the TMJ.
• Brief locking of the mandible on jaw opening and closure.
• Orofacial pain not associated with jaw movement may suggest another cause.

Associated Conditions

• Tension-type headache.
• Otological symptoms: otalgia, tinnitus, aural fullness, vertigo, subjective hearing impairment.

Physical Examination

Palpation

• TMJ and masticatory muscles for tenderness, abnormal mandibular movement, and signs of bruxism.

Jaw Opening

• Normal values: 35-45 mm; less than 25 mm suggests dysfunction.

TMJ Examination

• Place one finger in the ear canal to palpate the anterior canal wall during mouth opening and closing.
• Use a stethoscope to auscultate over the TMJ for crepitus.

Signs of Dysfunction

• Intra-articular Derangement: Tenderness on palpation, joint clicking, and crepitus.
• Muscular Problems: Pain on jaw movement, headache, and referred pain.

Other Examinations

• Otoscopy to exclude otological causes.
• Inspection of the oral cavity.
• Palpation of neck musculature.

Diagnostic Imaging

Indications

• Useful when history and examination findings are unclear.

Imaging Modalities

Plain Radiography and CT

• Reveals severe degenerative articular disease, rules out fractures and dislocations.

Panoramic Radiography (Orthopantomogram)

• Early screening tool to exclude common odontogenic causes and assess for joint pathology.

Ultrasonography

• Not sensitive for intra-articular osteoarthritis but useful for assessing disc position.

Magnetic Resonance Imaging (MRI)

• Gold standard for TMD diagnosis; assesses soft tissue structures, articular disc displacement, and joint effusion.
• Predominantly used for severe, treatment-resistant TMD and pre-operative planning.

Key Points

Differentiation

• Intra-articular Issues: Joint clicking, crepitus, articular disc displacement.
• Muscular Issues: Pain on jaw movement, tension-type headache, referred pain.

Role of Imaging

• Primarily used for severe or unclear cases.
• MRI preferred for detailed assessment of soft tissues and joint structures.

Management

Conservative Approach

Spontaneous Resolution

• Up to 40% of symptomatic patients may experience spontaneous resolution.
• 50-90% of patients find relief with conservative therapy.

Non-Pharmacological Treatments

Patient Education and Reassurance

• Important due to the association between TMD and cognitive factors.
• Cognitive behavioural therapy is beneficial for both short-term and long-term pain management.

Jaw Rest

• Avoid excessive jaw movements.

Soft Diet

• Reduces strain on the TMJ.

Warm Compress

• Applied over the region of pain.

Passive Stretching Exercises

• May improve the range of movement.

Behaviour Modifications

• Improve sleep hygiene.
• Stress reduction.
• Eliminate parafunctional habits (e.g., teeth clenching and grinding).

Splints

• Use is controversial; evidence is inconclusive.
• May benefit patients with severe bruxism and nocturnal clenching.
• Consider referral to a dentist for precise splint-fitting.

Intramuscular Botox Injections

• Efficacious in myofascial causes of TMD pain and tension-type headaches.

Physiotherapy

• Effective in improving joint range of motion.
• Referral should be considered in refractory cases.

Pharmacological Treatments

First-Line Agents

• Nonsteroidal anti-inflammatory drugs (NSAIDs) for acute and chronic pain.

Muscle Relaxants

• Benzodiazepines for recurrent masticatory muscle spasm and chronic bruxism.

Tricyclic Antidepressants

• Amitriptyline for chronic and regional pain disorders.

Medications with Little to No Benefit

• Tramadol, topical preparations (e.g., diclofenac), SSRIs, SNRIs, and MAOIs.

Opioids

• Not recommended due to the risk of dependency.

Referral and Specialist Management

Pain Specialist

• Consider for patients resistant to conservative measures, particularly with complex regional pain syndrome.

Maxillofacial Surgeon

• For patients unresponsive to conservative treatment.
• Severe pain and/or dysfunction of the TMJ.
• History of trauma or fracture of the TMJ complex.

Specialist Care for Red Flag Symptoms

• Persistent and worsening pain.
• Trismus.
• Cranial nerve abnormalities.
• Neurologic dysfunction.
• Concurrent infection.
• Systemic illness.
• Weight loss.
• Asymmetrical neck or facial swelling.
• Unilateral hearing loss.
• Vestibular dysfunction.
• New onset or unilateral tinnitus.

General Management Considerations

Trial Conservative Management

• Reasonable to trial for six to eight weeks before considering referral.

Complex Cases

• Referral to specialist care for persistent or worsening symptoms, or when red flag symptoms are present to rule out serious underlying conditions such as neoplastic causes.