Temporomandibular Syndrome

Etiology

The etiology of TMD is mildly understood, but it is believed to be multifactorial; the appropriate management of the condition requires recognizing the predisposing and contributing factors.[1]

Myofascial and intraarticular TMDs differ in their etiological factors. As the name implies, a myofascial disorder means that the muscles – in this case, the ones involved in mastication - are affected, becoming tensioned, fatigued, and painful. Several factors are linked to muscular dysfunction, including stress, parafunctional habits like bruxism and abnormal posture, psychological conditions like depression and anxiety, and autoimmune diseases.[1] Chronic pain conditions such as fibromyalgia are also often linked to TMD.[4]

Intraarticular disorders refer to inflammatory or mechanical factors that affect the joint itself, articular disc displacement being the most common.[1] Other intraarticular causes include trauma, capsular inflammation, osteoarthritis, hypermobility, and inflammatory diseases, like rheumatoid arthritis. It is not clear yet if malocclusion contributes to TMD.[1]

Epidemiology

TMD symptoms can appear at any age, but a peak incidence occurs in adults between 20 to 40 years.[1][5] Women are much more likely to be affected than men, the reason for which is still unknown.[1] Even though up to 60 to 70% of the population shows signs of TMJ disorders, only 5% to 12% of people report symptoms and require treatment.[2]

Pathophysiology

Masticatory Muscle Disorders

The most common symptoms observed include pain in the masticatory muscles when swallowing, speaking, and chewing. Pain increases with palpation or with manipulation of muscles. It is associated with restricted mandibular movements.

Temporomandibular Joint Disorders

Derangement of the Condyle-Disc Complex

The derangement of the condyle disc complex arises due to a breakdown in the rotational function of the disc. This condition can result from the lengthening of ligaments (discal collateral and inferior retro-discal ligaments) or thinning of the posterior disc border. The contributing factors can be micro or macro trauma.

Disc Dislocation with Reduction

Disc displacement can lead to partial or complete disarticulation of the disc from discal space in condyle–disc assembly. When the mouth is closed, the articular disc is displaced anterior to the condyle head; when the mouth opens, the disc repositions on the condyle head similarly to normal.[6] This on and off disc movement explains the click, snap, or pop sound in the TMJ. This sound does not appear with every movement of the mandible but with some frequency.[6] A normal range of motion is expected since the articular disc reduces during condylar translation.[6] Jaw deviation while opening the mouth can occur; the interincisal distance of disc reduction during opening is greater than when the disc is dislocated during the closure.

The disc can sometimes fail to reduce with consequent mouth opening limitation. This is known as disc displacement with reduction with intermittent locking.[6]

Disc Dislocation without Reduction

When the articular disc fails to reduce repeatedly, causing a limited mouth opening, the diagnosis of disc displacement without reduction is given.[6] The repositioning of the disc can become problematic due to the loss of elasticity in the superior retro-discal lamina. This situation causes forward translation of the condyle forcing the disc in front of the condyle. It presents as a locked jaw during the closure, represented as difficulty in maximum opening. The mandibular opening is around 25 to 30 mm, deflects towards the involved joint, and is associated with pain. The bilateral manipulation technique of loading the joint is painful due to the condyle position in the retro-discal tissues.

Structural Incompatibility with Articular Surfaces

The disorder results from changes in the smooth sliding surfaces of the TMJ. The alteration causes friction stickiness and inhibits joint function. Structural incompatibility classifies as a deviation in form, adhesions, subluxation, and spontaneous dislocation.

Deviation in the Form

The physiological aging or minor degeneration of the condyle, disc, and fossa can cause deviations and dysfunction, significantly affecting mandibular movements.

Adherences and Adhesions

An adherence represents a brief hold of the articular surfaces. Adhesion can happen between the condyle and disc or the disc and fossa. Adhesions result from a fibrous connective tissue or loss of lubrication between the structures. It is characterized by restriction in the normal translation of the condyle movement with no pain. In chronic situations, the patient senses an inability to get the teeth back to occlusion during the closure.

Subluxation

It is a non-pathologic condition, a repeatable clinical phenomenon characterized by a sudden forward movement of the condyle past the crest of the articular eminence during the final stages of mouth opening. The steep, short posterior slope of the articular eminence and the longer anterior slope - more superior to the crest - cause the condyle to subluxate. The examiner can witness it by requesting the patient to open wide, creating a small void or depression behind the condyle.

Luxation (dislocation)

A dislocation happens when the condyle moves in front of the articular eminence and cannot descend back to the normal position.[7] Dislocations result from the TMJ's hyperextension, causing the fixing of the joint in an open position during the opening of the mouth. It can be partial (subluxation) or complete (luxation). It can be acute or chronic (protracted or recurrent), bilateral or unilateral.[7] Anterior teeth are usually separated, and the posterior teeth are closed. The patient will find difficulty closing the mouth and pain.

Inflammatory Disorders of the TMJ

The joint disease of inflammatory origin characteristically presents with deep continuous pain commonly accentuated on functional movement. This constant pain can trigger secondary excitatory effects. It expresses as referred pain, sensitivity to touch, protective contraction, or a combination of these problems.

Inflammatory joints are classified according to the structures involved into synovitis, capsulitis, retro-discitis, and arthritis.

Synovitis/Capsulitis

Trauma can cause inflammation of the synovial tissues (synovitis) and the capsular ligament (capsulitis). It presents as continuous pain, tenderness on palpation, and limited mandibular movement. However, it isn't easy to differentiate between these two entities clinically, and arthroscopy is helpful for diagnosis.

Retrodiscitis

It is caused by trauma or progressive disc displacement and dislocation. The patient complains of pain, which increases with clenching. Limited jaw movement, swelling of retro discal tissues, and acute malocclusion are associated with the disease.

Arthralgia

The pain originates in the jaw and is affected by jaw movement, function, or para-function. The pain can be replicated with provocative testing of the TMJ.

Arthritis

Pain originates in the joint, and features of inflammation or infection over the affected joint are usually seen, such as edema, erythema, or increased temperature. Further symptoms include dental occlusal changes, e.g., ipsilateral posterior open bite if intraarticular with unilateral swelling or effusion. This disorder is also known as synovitis or capsulitis, although these terms limit the sites of nociception. TMD is a localized condition; there should be no history of systemic inflammatory disease.

Osteoarthritis

It is an inflammatory disorder that arises due to an increased joint overload. The increased forces soften the articular surfaces and resorb the subarticular surface. The progressive loading and the subsequent regeneration cause loss of the subchondral layer, bone erosion, and osteoarthritis. The condition characterizes by joint pain that increases with movement. It is also associated with disc dislocation and perforation.

Osteoarthrosis

Arthrosis is the adaptive unaltered arthritic changes of the bone due to decreased bone loading. It occurs after the overloading of the joint, mainly due to parafunctional activity, and is often associated with disc dislocation.

Systemic Arthritis

Several arthritides can affect the TMJ, including traumatic arthritis, infectious arthritis, and rheumatoid arthritis.

Chronic Mandibular Hypomobility

It is a long-term painless restriction of the mandible. Pain only occurs when using force to attempt opening beyond limitations. Hypomobility can be caused by ankylosis, muscle contracture, or coronoid process impedance.

Growth Disorders

Growth disturbances can affect the TMJ bones or muscles. Common growth disturbances of the bones are agenesis (no growth), hypoplasia (insufficient growth), hyperplasia (excessive growth), or neoplasia (uncontrolled, destructive growth). Common growth disturbances of the muscles are hypotrophy (weakened muscle), hypertrophy (increased size and strength of the muscle), and neoplasia (uncontrolled, destructive growth). The growth alterations typically result from trauma.

History and Physical

The clinician should perform a thorough medical and dental history emphasizing the location, onset, and characteristics of pain, aggravating and relieving factors, past treatments, and history of other pain disorders.

Recommended Systematic and Psychological Assessment

Temporomandibular disorder symptoms include pain, TMJ clicking and crepitation, and different levels of mandibular limitation. The pain is typically provoked by function; spontaneous pain in the TMJ area suggests a different etiology.[8] Pain can refer to the neck and scalp and tends to be exacerbated by masticating, yawning, or talking for long periods.[1] A click, crepitus, or pop when opening or closing the mouth may be associated with anterior disc displacement or osteoarthritis.[9]

Patients with TMD also report headaches and otological symptoms – otalgia, tinnitus, vertigo, aural fullness, and subjective hearing impairment.[1] However, otological symptoms are more common in myofascial disorder, which is believed to be due to the shared embryological origin of some middle ear structures and masticatory muscles.[10]

The physical examination should also search for signs of tooth wear, bruxism, abnormal mandibular movements, tenderness of muscles of mastication, neck, and shoulder, pain with dynamic loading, and postural asymmetry. A neurological examination rules out cranial nerve abnormalities. Careful palpation of masticatory muscles and surrounding neck muscles helps identify trigger points, myospasm, and referred pain syndrome.[11][12]

Pain

Pain from the TMJ and muscles of mastication is a common symptom. It can be a constant or periodic dull ache over the joint, the ear, and the temporal fossa. It is more commonly observed during mandibular movement or palpating the affected regions. The pain can be myogenic, caused by mechanical trauma and muscle fatigue. Articular pain arises from overloading, trauma, or degenerative changes of articular and periarticular tissues.[13][14]

Joint Sound

The two common joint sounds are clicking and crepitations. Clicking is a sound of an uncoordinated movement of the condylar head and the articular disc. Crepitations are compound sounds caused by the roughened, irregular articular surfaces during mandibular movement.

Limitation of Mandibular Movement

Movement limitation can occur in opening, closure, protrusion, and lateral excursion of the mandible. It can be due to muscular or ligamentous restriction or disc displacement.

Dislocation

It is the condyle displacement from the fossa, and the patient may be unable to close the mouth. The patient can reduce the dislocation himself or report to the clinician for reduction.

Otologic Symptoms

TMJ pain in the auricular regions is more noticeable posteriorly. Tinnitus, itching in the ear, and vertigo are other symptoms associated with articular pain.

Recurrent Headaches

Patients perceive the pain and tenderness of masticatory muscles along the temporal region as headaches. It can correlate with other headaches, such as migraine pain.

Evaluation

Pain on mandibular movement, headaches, and referred pain point towards a muscular cause; tenderness on TMJ palpation and joint sounds suggest an intraarticular problem.[1] Evaluating the oral cavity, the inner ear (otoscopy), and palpating the neck musculature help exclude other causes of facial pain.[1]

Magnetic resonance imaging (MRI) is the preferred imaging study to assess the TMJ due to its capacity to accurately show joint effusion, disc displacement, and soft tissues.[15] However, a simple panoramic X-ray can help rapidly evaluate the state of the dentition and joint and tends to be the initial investigation. Plain radiographs and CT scans can show severe joint degeneration, fractures, and dislocations.[1] Ultrasonography shows the disc position, but it does not help diagnose osteoarthritis.[1] Computed tomography (CT) and magnetic resonance imaging (MRI) are more beneficial in severe, chronic, or suspected structural abnormalities of TMJ.[16][17] Additionally, newer techniques of nerve blocks, botulinum toxin injections, arthrography, and mandibular motion data can prove to be of significant diagnostic benefit.

Treatment / Management

Conservative treatment reduces symptoms in 50 to 90% of patients and should be adopted first. Conservative methods include patient reassurance and education, a soft diet, jaw rest, warm compresses on the painful area, and passive stretching.[18][1] Indicating occlusal and non-occlusal splints for TMD treatment remains controversial and not well supported by evidence.[19](A1)

Behavioral Changes

Muscle activity alters due to increased levels of emotional stress. Managing patients' stress is particularly important in treating TMDs. Behavioral changes like improving sleep hygiene, reducing stress, and treating parafunctional habits can significantly improve symptoms.[1] Cognitive-behavioral therapy benefits patients with TMD for short- and long-term treatment.[1]

Patient Awareness 

Educating patients regarding the relationship between muscle hyperactivity and stress improves patients' behavior towards the condition, psychological health, and temporomandibular disorder.

Restrictive Use

In most TMDs, patients complain of pain in the TMJ and restricted mandibular movement. The clinician can instruct the patient to move the mandible within a trouble-free range of motion, promoting psychological health and pain management.

Voluntary Avoidance

The teeth contact can trigger pain in some cases. Patients must try to reduce dental contact time, except during mastication, swallowing, and speaking. Clinicians can teach patients how to disengage the tooth to diminish pain and discomfort. A simple exercise of lip puffing can disengage teeth and enhance patient health.

Physiotherapy

Stretching exercises can improve the range of motion but not always alleviate the pain.[1] The commonly used manual techniques are soft tissue mobilization, joint mobilization, muscle conditioning, resistance exercises, passive muscle stretching, assisted muscle stretching, and postural training. Other physical therapy modalities include thermotherapy, ultrasound, electro galvanic stimulation, and cold laser.

Pharmacological Treatment

The first-line drugs for treating acute and chronic forms of TMDs are non-steroidal anti-inflammatory drugs (NSAIDs).[1] Benzodiazepines can be prescribed for cases of recurrent masticatory muscle spasms and bruxism when relaxation techniques have failed.[20] Tricyclic antidepressants may be prescribed as a trial since they improve symptoms of other pain disorders.[1](A1)

Invasive Procedures

Invasive strategies include intra-articular long-acting corticosteroid, hyaluronic acid, and botox injections. These interventions are recommended once conservative therapies have failed or in severe acute exacerbations.

Intra-articular steroids are indicated in the acute treatment of osteoarthritis of the TMJ, but multiple doses can lead to the destruction of articular cartilage.[21][22] There is only limited evidence regarding the efficacy of hyaluronic acid injections in treating acute exacerbations.[23](A1)

Botulinum toxin injections are used to treat painful trigger points and chronic bruxism, but a recent Cochrane study found inconclusive evidence for myofascial pain.[24][25](A1)

Differential Diagnosis

Various other disorders can present as facial, ear pain, and headaches and should be included in the differential diagnosis for TMDs.

• Common causes of facial pain are trigeminal, glossopharyngeal, and post-herpetic neuralgia, sinusitis, salivary gland disorders, and carotidynia.
• Common causes of orofacial pain are dental caries, dental abscess, dental eruption.
• Common causes of headaches are migraines, cluster headaches, and temporal arteritis.
• Common causes of ear pain or stuffiness are middle ear infections, injuries, barotrauma, and Eustachian tube dysfunction.

Prognosis

Up to 40% of patients report the remission of symptoms without any intervention,[26] and most patients have a favorable response to conservative treatment.[1] A small number of patients develop refractory or persistent TMD. There are no known risk factors associated with chronic TMD. But, recently published data correlated heightened sympathetic tone with chronic TMJ pain.[27]

Complications

Temporomandibular disorder classic triad includes pain in the temporomandibular joint, reduced mandibular range of motion, and functional clicking. This can impair patients' capacity to perform everyday tasks such as eating, speaking, or yawning, significantly impacting their quality of life.