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Etiology (Causes) of Temporomandibular Disorders (TMDs)

Updated: Apr 26

Welcome to my third post in an ongoing series on temporomandibular disorders (TMDs). To read the previous posts, click the titles below.


 


TMD is not a specific diagnosis. It is an umbrella term for various conditions affecting the jaw, muscles, and associated structures.



Today’s focus is on the etiology/causes of temporomandibular disorders.



Etiology (Causes) of Temporomandibular Disorders


Etiology (Causes) of Temporomandibular Disorders (TMDs)


If you have been diagnosed with a TMD, you may wonder what caused it or predisposed you to experience painful symptoms or dysfunction.


 

The etiology (cause) of temporomandibular disorders is multifactorial, meaning that there are multiple reasons why different people experience TMD symptoms. All causes and factors associated with TMDs are not fully understood. Some individuals may have multiple predisposing factors; for others, no known cause may be identified.


 

Some factors can initiate TMD symptoms, such as direct trauma to the jaw. Some other factors can predispose susceptible individuals to experience TMD symptoms, for example, joint hypermobility. And, some factors can perpetuate TMD symptoms and prevent healing and restoration, such as teeth clenching and grinding.

 

 

Below is a list of SOME etiological factors associated with the onset of Temporomandibular Disorders (TMDs):


 

1. Trauma

Patients with TMDs are more likely to report a history of trauma to their jaw than individuals who do not have signs and symptoms of TMDs.


 

Direct trauma to the mandible or TMJ can result from physical impact or injury to the jaw. Trauma can also result from prolonged and sustained hyperextension of the jaw for surgical intubation, dental procedures, and even forceful yawning.

 

The consequences of trauma may include:

  • Pain and inflammation of the joints and muscles

  • Displacement of the articular disc

  • Stretching of the ligaments

  • Condylar and sub-condylar fractures

  • Other TMJ derangements

     



Oral Parafunctional Habits

 

2. Microtrauma

Habits that perpetually increase the loading of the joint.

Microtrauma refers to low-grade forces that lead to physical damage over a prolonged period. Parafunctional habits, a common source of microtrauma, are overuse habits that involve repeatedly and habitually using a body part beyond what is necessary for normal function.


Oral parafunctional habits include:

  • Teeth clenching, grinding, bracing, and tapping

  • Gum chewing

  • Nail/cuticle biting

  • Cheek biting


The teeth should only occlude transiently while talking, chewing, or swallowing. When the jaw is not in function, teeth should be at rest and unclenched. When teeth are consistently clenched and in function, it increases the load on the TMJ and activates the jaw-closure muscles.



In susceptible individuals, pain ensues when the loading exceeds the ability of the TMJ to adapt to excessive function. However, research has also shown that not all patients who habitually clench and grind their teeth develop TMD-related symptoms.


 

3. Poor posture, e.g.,

  • Forward head position

  • Bracing your phone between your head and shoulder

 

A good posture is foundational to maintaining the healthy function of the entire musculoskeletal system. You may have experienced lower back or shoulder pain after sitting in a slouched and uncomfortable position for a prolonged period. The same applies to the TMJ and associated structures.



The neck, shoulder, and upper back muscles support the head, and pain can be referred to the head from the neck. Poor head, neck, and shoulder posture can strain the muscles of mastication and cervical muscles leading to pain and dysfunction.


 



4. Occlusion

Occlusion is important and occlusal concepts must be adhered to in dentistry. If you have ever had a tiny piece of food get stuck in a molar pit or fissure, you know how irritating that can feel.


 

That being said, historically, the dental profession greatly emphasized occlusal factors as the primary etiologic factor for TMDs. A heavy focus was placed on occlusal adjustments and major dental rehabilitation as the primary way to treat patients with TMDs.


 

Available evidence does not support a significant role for occlusion in the development of TMDs.Occlusal equilibration and rehabilitation are not generally recommended due to the irreversible nature of the treatment.

 


Clinicians are encouraged to view TMDs as a multifactorial disorder with both biological and psychosocial input.

 


Genetics in TMDs

 

5.  Genetic factors

Studies have shown that some genes may be associated with the development of TMDs, especially when combined with other physical, environmental, and psychosocial factors. However, more studies on genetic associations are needed.

 

 

6. Generalized joint hypermobility

Patients with generalized joint hypermobility disorders are more likely to experience TMJ disc displacement and open locks than the general population.




 

7. Co-morbid medical conditions

 

Individuals with fibromyalgia who experience widespread musculoskeletal pain are more likely than the general population to develop myofascial pain in the muscles of mastication as a component of their underlying condition.


 

Patients with autoimmune conditions, which cause pain and inflammation in multiple joints, can also experience involvement of the TMJs. Examples of autoimmune conditions that can involve the TMJs include:

  • Rheumatoid arthritis

  • Psoriatic arthritis

  • Juvenile arthritis

  • Systemic sclerosis/scleroderma

  • Systemic lupus erythematosus (SLE)


 

 8. Co-morbid behavioral and psychosocial factors such as:

  • Stress

  • Anxiety/depression

  • Poor sleep

  • Major life events



There is evidence that orofacial pain, including TMDs, may be one of the somatic (physical) symptoms of emotional distress. Patients tend to report higher intensity of facial pain, jaw pain, and headaches during periods of intense stress and poor sleep quality. During such periods, patients may exhibit habits such as teeth clenching and bruxing (grinding), which increases muscle activity and non-functional loading of the temporomandibular joint.


 

Pain is one of the most common sleep disrupters, and poor sleep quality contributes to more intense pain and a greater level of disability from pain. Emotional distress and insufficient sleep upregulates the sympathetic nervous system lowering the threshold and our brain's capacity for pain perception.


 

In Conclusion

Not everyone with the etiological factors listed above will experience TMD. However, individuals with chronic TMD symptoms are more likely to have multiple risk factors that act together over a prolonged period, leading to the development and persistence of TMD-related signs and symptoms.



Join me next time as I discuss the signs and symptoms of TMDs (Temporomandibular Disorders).

 

Until next time…

 

Dr. Chizobam Idahosa





© Etiology (Causes) of Temporomandibular Disorders (TMDs). Dr. Chizobam Idahosa.


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