Common Causes of TMD

Like any joint in the body, the TMJ’s are subjected to wear and tear, trauma (micro and macro), disease, degeneration, and growth and developmental abnormalities.

Arthritis

Arthritic changes occur when there is a breakdown of the joint that leads to degeneration and an inflammatory condition that can affect any joint in the body. Various forms or arthritis such as Osteoarthritis (degenerative), Rheumatoid, Infectious, Psoriatic and others can all cause pain in the TMJ’s. Repetitive micro and macro trauma can also cause degeneration of the TMJ’s. The prevalence of arthritic changes in the jaw joints increases with age but is by no means an ‘Older Persons’ disease. Primary arthritic disease is seen in older people from wear and tear and is usually asymptomatic. When symptoms do occur they often present as mild complaints with some developing into severe pain and limited mouth opening.

CT image of TMJ

Secondary degenerative arthritis occurs as a result of trauma or chronic clenching and bruxing and is usually seen in younger people. The presenting symptoms are often much more severe than seen in primary arthritis.

Bruxism

Generally, bruxism (grinding of the teeth) occurs when a person is asleep which is why so many people don’t even realise they do it. Forces generated during sleep bruxism can be very high and cause significant damage to the teeth and is obvious, whilst in many other people it is a low grade but chronic and repetitive condition. Injury to the TMJ’s can develop from this constant grinding of the teeth from excessive forces to the ligaments, disc, and articulating surfaces of the jaw joints. At the very least, bruxing will produce muscle pain and sore jaw muscles especially when waking in the morning.

Clenching

In many ways clenching of the teeth can lead to more painful conditions than bruxing and is even more difficult to diagnose. Teeth should never contact except lightly during chewing. When teeth are held together or the jaw is held tense over a period of time such as when concentrating, the facial and neck muscles become fatigued and painful. Morning and afternoon headaches, difficulty chewing, neck pain, and sore facial muscles are the most common reported symptoms. When clenching becomes chronic such as day and night, many severe muscle related symptoms can occur that can have dramatic effects on a patients quality of life.

Growth and Development

The TMJ’s are a part of the body and as such are also subject to problems such as tumours, abnormal growth, developmental delays, syndromes, and diseases. Although relatively rare, congenital and developmental anomalies, and neoplasms of the TMJ are important to identify early in life to re-establish normal growth of the mid-face, and in adults to limit the amount of change and destruction that can occur within the facial bones and TMJ’s. Other diseases can also affect the TMJ’s and cause facial and jaw pain.

Conditions and diseases that can occur include:

Condylar agenesis
Condylar hypoplasia
Condylar hyperplasia
Hemifacial microsomia
Ankylosis of the TMJ
Sjogren’s Syndrome
Systemic Lupus Erythematosis
Scleroderma

The most common tumours of the TMJ’s are benign and include:

Chondromas
Osteomas
Osteochondromas

Rarely seen are Fibrous Dysplasia, Giant Cell Reparative Granuloma, and Chondroblastoma. Even less frequently seen are the malignant Fibrosarcoma and Chondrosarcoma.

Muscle overactivity

When the muscles of the head and neck are overused, just like any other muscle in the body, pain will develop. The muscles that most commonly become tender that will cause facial and TMJ pain and headaches are the Masseter, Anterior Temporalis, Medial Pterygoid, Trapezius, and Sternocleidomastoid muscles.

Overuse of facial and neck muscles can develop from teeth clenching and grinding, habits that cause the jaw to be held in an abnormal position or for long periods such as pen/pencil chewing, violin playing, lip and nail biting, resting your chin in the palm of your hand, and poor body posture.

Recognised disorders of the head and neck muscles are characterised by pain from pathological or functional changes in a muscle group. They include:

Myositis – an acute condition with inflammation of the muscle and its connective tissue attachments that results in pain, swelling, and a decreased range of motion. Causes include overuse, infection, or trauma.
Muscle spasm – is an acute contraction of a muscle caused by overuse or overstretching of a muscle. It is often referred to as ‘guarding’ following an acute injury. If left untreated, muscle spasm in the contracted state can result in fibrous scarring and permanent contracture of the muscle will develop.
Trismus – is a decreased range of motion due to infection or psychological causes (hysterical trismus).
Fibromyalgia – diffuse, firm, painful muscular bands (trigger points) develop and are often associated with a sleep disorder. Pain follows known referral patterns of these trigger points and can often be reproduced by applying pressure to them.

Examples of Trigger Points
In all examples, the black x marks where in the muscle the central trigger point can be found, whilst the solid red shaded area is the main pattern of referred pain. The stippling or ‘dotted’ red area is the spill over areas of referred pain. (Images reproduced from Travell and Simons).

Trigger Points

Synovitis

A synovial membrane lines the TMJ and produces a fluid that lubricates the joint and allows it to function smoothly. An inflammatory condition of the synovial membrane will produce pain and can cause limited movement within the TMJ. Rheumatoid arthritis can cause a Synovitis in the TMJ’s.

Trauma

Macro trauma such as motor vehicle accidents, assaults, sporting injuries, falls, difficult dental and wisdom tooth extractions, and any other incident where a sudden blow or shock to the jaw joints occur, can cause a TMD. In the majority of cases, macro trauma will cause an immediate level of pain and concern that requires urgent treatment such as a blow to the side of the head, or a fall. In some cases however, the initial precipitating injury often may be very subtle and occur years previously, and even as a child. The injury therefore is overlooked as symptoms resolve over a period of weeks, but may return or develop later in life to a level that treatment is sought.

Micro trauma is a consistent and repetitive low-level grade of stress to the TMJ system over a period of time. It most commonly occurs as a result of continual teeth clenching and teeth grinding that overwhelms the TMJ’s shock absorber ability to tolerate the forces that are generated. A majority of microtrauma occurs when we sleep, as this is when forces from teeth clenching and grinding are at their greatest.

Occlusion

Missing teeth, severely worn teeth, poorly fitting dentures, and malocclusions are all associated with TMD. Whilst not a direct cause, many people that develop a TMD also have these problems with their bite.

Body Posture and TMD

Recently, many studies have shown that a relationship exists between your teeth and bite, your jaw joints, head position, head and neck muscles, lower back, pelvis, your feet, and your posture. The musculoskeletal system therefore can often be a factor in many types of pain or functional conditions, and a problem in any one of these areas may, and often does contribute to a problem in another part of the body.

Poor posture, particularly of the head and shoulders results in overactivity of the muscles that support these parts of the body and leads to fatigue, pain, and trigger points. A forward head posture is a major contributor to headaches that occur in the afternoon. Assessment, treatment, and long-term management of TMD symptoms require focus on and correction of postural problems to help adequately reduce muscle orientated pain and dysfunction.

Good posture

Posture images adapated with kind permission from Dr James Carlson DDS

Snoring and Sleep Apnoea

Increasingly research is showing that the airway and sleep disorders are a major factor that contributes to patients developing a TMD and chronic facial pain problems. In those people who snore or have Obstructive Sleep Apnoea (OSA) often grind their teeth excessively as the jaw is constantly pushed forward during sleep in an attempt to open the airway. This condition is known as Sleep Bruxism. Over time, excessive tooth loss and constant forces on the facial muscles and TMJ's can lead to pain and dysfunction. In our practice, approximately 10% of patients with TMD have an undiagnosed sleep disorder. And the same applies for patients that suffer from snoring and sleep apnoea. Approximately 10% have a jaw joint problem or have excessive tooth wear that needs to be addressed and managed whilst treating the sleep disorder.

Orthodontics

There is still much debate and controversy that continues to rage around the world regarding orthodontics and the development of TMD problems. Many orthodontists will swear that orthodontics has nothing to do with TMD and in no way causes any problems. Comments to patients such as “You will grow out of it” and “It is only muscle spasm” can be very misleading and dangerous. Fortunately there are not too many orthodontists who hold this view as the general current consensus is that there are certain people that may be ‘at risk' of developing a TMD during orthodontic treatment, just like there are people at risk of developing many other types of health problems. This view is more likely to be a more accurate evaluation of the relationship between orthodontics and TMD. When a TMD is identified before, during, or soon after orthodontic treatment, it is very important that the patient tell the treating orthodontist so that the TMD can be assessed and treated immediately.

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