Temporomandibular disorders (TMD) encompass a range of conditions affecting the masticatory system, including the temporomandibular joints and associated musculature such as the masseter and temporalis. These disorders can lead to mild to moderate pain, limitations in jaw movement, and clicking sounds, among other symptoms. In this article, we will delve into the various aspects of TMD, including its prevalence, risk factors, diagnostic process, treatment approaches, and ongoing research in the field. This article draws from our podcast conversation with Dutch researcher Corinne Visscher, an expert in the field of TMD and an assistant professor at the Academic Center for Dentistry (ACTA) in Amsterdam.

Prevalence and Incidence of TMD

TMD affects approximately 10-12% of the population, with mild to moderate symptoms being common. However, the prevalence of treatment needs is lower, around 5%. Only a small percentage of patients with TMD seek specialized care from physical therapists or dentists. The annual incidence of TMD is estimated to be around 1-2%, highlighting the significance of this condition in healthcare.

Understanding TMD: Risk Factors and Patient Characteristics

TMD is more commonly observed in females aged 20-50, although it can also affect males and individuals from different age groups. In children, clicking sounds or locking of the joint is more common, whereas in elderly people, TMD is more related to degenerative disorders. Risk factors for TMD include oral behaviors such as teeth grinding and clenching, psychosocial factors like anxiety and depression, and genetic predisposition (Visscher et al. 2015). This predisposition might be due to
specific genes coding for neurotransmitters and pain transmission, so it’s more related to chronic pain in general than a specific risk factor for TMD in particular. While there’s not a strong association between TMD and tension-type headaches, the prevalence of migraine is twice as high in TMD patients as compared to the general population (Yakkaphan et al. 2022).  A study by van der Meer et al. (2017) also shows that bruxism, so clenching and grinding one’s teeth is not only a risk factor for TMD, but also a risk factor for migraine.
A couple of decades ago it was assumed that posture was a risk factor to develop TMD. However, there is no evidence showing that posture is an etiological factor for TMD (Visscher et al. 2002)

Diagnostic Process and Clinical Examination

There are no specific red flags that need to be screened for in the temporomandibular region, but severe pain, pain that wakes a patient up at night, or a constant increase in pain are atypical presentations for TMD and warrant a referral.  Clinicians also need to consider the presence of yellow flags which can be evaluated with short questionnaires like the PHQ-4. Depending on the dominance of yellow flags, multidisciplinary treatment might be necessary.
To diagnose TMD, three variables need to be present for TMD to be diagnosed: mild to moderate pain in the orofacial region, fluctuating pain (for example more severe when waking up), and pain increase in function such as chewing or wide opening of the mouth.
The diagnostic process for TMD involves a thorough clinical examination of the masticatory system. This includes assessing the range of jaw movements, identifying clicking sounds, and palpating the joints and muscles.

To distinguish joint problems from muscle problems in the temporomandibular area, dynamic and static resistance testing can be used (Visscher et al. 2009). For dynamic testing, the examiner applies counterresistance to the movements of mouth opening, closing, and protrusion of the mandible. During static testing, counter resistance is applied against the same directions of movement, only the mandible is not moving. This way, only muscle tissue is provoked.
While internal muscle palpation was regularly used in the past, studies showed that this has a low validity as intraoral palpation is painful, even in healthy subjects (Türp et al. 2001).
In case a patient suffers from a disk displacement, joint play testing – so traction, and translation techniques, can be informative.
Patients should also be questioned for headaches as one form of secondary headache is the one directly attributed to TMD (Olesen 2018). To classify as this form of headache, there needs to be causation demonstrated by at least 2 of the following:

1. the headache has developed in temporal relation to the onset of the temporomandibular disorder or led to its discovery
2. the headache is aggravated by jaw motion, jaw function (eg, chewing), and/or jaw parafunction (eg, bruxism)
3. the headache is provoked on physical examination by temporalis muscle palpation and/or passive movement of the jaw

Treatment Approaches for TMD

Treatment of TMD varies based on the subtype and severity of the condition.  Generally, the prognosis for TMD is good. Even in the case of a disk displacement, symptoms – when treated – generally resolve within 6 weeks to 3 months. Changing oral habits and tackling psychosocial factors are fundamental in managing TMD-related symptoms.  Myofeedback devices can be a great addition to show a patient to relax their masticatory muscles.
Additionally, interventions such as massage techniques, stretching exercises, and mobilization procedures can be effective in addressing muscle and joint-related issues. While it is usually sufficient to see patients once a week, they should be encouraged to perform home exercises 2-3 times per day such as intra-oral stretching of the masseter muscle with their thumbs as well as passive opening of the mouth.
While posture is not associated with the development of TMD, some studies suggest that changing posture can have a positive influence on temporomandibular complaints (Wright et al. 2000). Patients presenting with an acute anterior disk displacement without reduction after a force to the jaw, like in bike or sports accidents might benefit from manipulation of the disk.
For patients with chronic TMD, a multidisciplinary approach involving orofacial physical therapists and dentists may be necessary to optimize outcomes.

Research & Future Directions

Many patients with chronic complaints in the temporomandibular region see many different specialists before they are eventually treated by a TMD specialist. Current research in the field of TMD is focused on understanding the journey of patients with chronic TMD, identifying early screening criteria, and improving the diagnostic and treatment pathways.
Collaborative efforts between healthcare professionals, including physical therapists, dentists, and specialists, are essential in enhancing the management of TMD and related conditions.

For further information on TMD and related topics, healthcare professionals can refer to reputable resources such as the Diagnostic Criteria for TMD and academic institutions specializing in orofacial pain and dysfunction. Continuous education and collaboration within the healthcare community are vital in addressing the multifaceted nature of temporomandibular disorders and optimizing patient care.

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In this blog post, we aimed to provide a comprehensive overview of temporomandibular disorders (TMD) for healthcare professionals. The content covered various aspects of TMD, including its prevalence, risk factors, diagnostic process, treatment approaches, and ongoing research in the field. The information presented is intended to enhance the understanding of TMD and facilitate informed decision-making in clinical practice.

References

Olesen, J. (2018). International classification of headache disorders. The Lancet Neurology, 17(5), 396-397.

Türp, J. C., & Minagi, S. (2001). Palpation of the lateral pterygoid region in TMD—where is the evidence?. Journal of dentistry, 29(7), 475-483.

van der Meer, H. A., Speksnijder, C. M., Engelbert, R. H., Lobbezoo, F., Nijhuis-van der Sanden, M. W., & Visscher, C. M. (2017). The association between headaches and temporomandibular disorders is confounded by bruxism and somatic symptoms. The Clinical Journal of Pain, 33(9), 835-843.

Visscher, C. M., & Lobbezoo, F. (2015). TMD pain is partly heritable. A systematic review of family studies and genetic association studies. Journal of oral rehabilitation, 42(5), 386-399.

Visscher, C. M., De Boer, W., Lobbezoo, F., Habets, L. L. M. H., & Naeije, M. (2002). Is there a relationship between head posture and craniomandibular pain?. Journal of oral rehabilitation, 29(11), 1030-1036.

 Wright, E. F., Domenech, M. A., & FISCHER JR, J. R. (2000). Usefulness of posture training for patients with temporomandibular disorders. The Journal of the American Dental Association, 131(2), 202-210.

 Yakkaphan, P., Smith, J. G., Chana, P., Renton, T., & Lambru, G. (2022). Temporomandibular disorder and headache prevalence: A systematic review and meta-analysis. Cephalalgia Reports, 5, 25158163221097352.