Bruxism is a disease which dominantly derives from the masticatory muscles

Bruxism is not a disease but a collective term for abnormal mouth habitual activity together with increased jaw-muscle activity (Lobbezoo et al. 2018). The complexity of the neurophysiological mechanism has been poorly understood until now. Risk factors (anatomical, psychosocial, and/or neuromuscular) are complex and the interference of the different risk factors are controversial (Manfredini et al 2013).

Bruxism belongs to the sub classification of myofascial TMD (Axis I, DC/TMD consortium)

The general belief of physical therapists is that bruxism is a kind of myogenic TMD which is increased by stress; which is not true. TMD, such as difficulty closing and opening the mouth, jaw locking, temporomandibular joint sounds, and a feeling of stiffness or jaw fatigue, can be a possible risk factor for bruxism (Ciancaglini et al., 2001). Feeling of stiffness or jaw fatigue is more frequently seen in sleep bruxism; whereas, awake bruxism is more associated with joint sounds and depressive mood (Selms et al., 2004; Manfredini et al., 2013). A recent study confirmed that when there is an increase severity of TMD with increased neck disability and pain the prevalence of bruxism is increased (von Piekartz 2019).

Bruxism is dominantly peripherally stimulated and had therefore a dominant input trigger

Palpation of masticatory muscles, especially the masseter and temporal muscle may be significantly sensitive in bruxers but is it fair to hypothesize that there is a causal relationship between hypersensitivity, increased muscle tone and the bruxers complains? In patients with bruxism these signs are mainly centrally mediated, not peripherally. There is convincing evidence, however, that (sleep-related) bruxism is part of an arousal response. Disturbances in the central dopaminergic system have been implicated in the etiology of bruxism as well. Further, there is a role for factors like smoking, alcohol, diseases, trauma and heredity, while the proposed role of stress and other psychological factors is probably smaller than previously assumed (Lobbezoo e and Naeije et al 2001, Lobbezoo et al 2018 ).

Bruxismus and Bracing are two different phenomena

Most physical therapist are convinced that bruxism in grinding during the night and bracing is different from clenching during the day. This is the wrong premise. Somnography and polysomnography studies have shown that clenching and grinding are (unconscious) mechanism with teeth contact during the day or at night (Raphael et al 2013, Muzalev et al 2017).

Posture changes, especial forward head posture, causes an increased masticatory system activity and leads to bruxism

From different studies it is know that there is no clear evidence for the existence of a predictable relationship between occlusal and postural features. It is clear that the presence of bruxism (and also TMD) is not related with the existence of measurable occluso-postural abnormalities in adults (Cesar et al 2006, Manfredini et al 2012 ). In children, head posture, TMD, craniofacial morphology and bruxism seems to be minor to moderate associated with each other (Kritsineli et al 1992, Motta et al 2011).

Bruxers need a splint from the dentist because the bite is a causal factor

Patients and therapist are often influenced by the media or not scientific, commercial publications that a splint may help to get rid of (the complains caused by) bruxism. Based on several reviews, it should be concluded that there is no evidence what-so ever for a causal relationship between bruxism and the bite (Lobbezoo et al 2012). Definitive occlusal adjustment measures therefore should not be used for the causal treatment of bruxism. Splints are nowadays commonly used to protect the teeth because they reliably prevent excessive attrition-type tooth wear by interrupting tooth-to-tooth contact. Therefore, they may be worn on the maxilla as well as the mandible. Only in children should short-term splint therapy can be considered. After the completion of tooth development, splints can be used in children in basically the same manner as in adults. (A3 German Guideline Bruxism)

Bruxers commonly have orofacial pain, headache and are restricted in their daily life.

Bruxism behavior does not directly lead to orofacial pain, headache or restrictions in daily life. According an overview study the prevalence of bruxism in orofacial and or headaches varying between 6% and 91% but 60% of all bruxers seems to have no complains (Lobbezoo et al 2009, Paesani 2010). It is the potential risk factors of bruxism which interfere and leads to complex pathophysiological changes like increase of trigeminal sensitivity and therefore pain experiences (Molina e t al 1997). Bruxism does not restrict a person’s daily life but polysomnograph studies have found that sleep bruxism is associated with sleep changes during the night which may influence concentration and fitness (Lavigne et al 2007,Bader et al 2000).

Neck disability and pain in Bruxers is mostly related to cervical impairments

In daily practice bruxers often seem to have neck pain. During assessment (muscle and joint palpation, physiological and accessory movements) the neck tests may be painful and mobility may be changed. Neck impairments are present in people with TMD and may be one of the risk factors of bruxism (Lobbezoo et al 2012), but is there a clear relation between cervical dysfunctions/impairments and bruxism? In a recent study it was noted that severity of bruxism is independently associated with cervical impairments. Pain associated with cervical movement tests without clear cervical impairments was found to be correlated with bruxism. Therefore, physical therapist need to be aware that signs of cervical movement impairment are not likely to be the cause of the bruxism. The coordination is probably related to an increased trigeminal sensitivity which causes false positive neuromusculoskeletal tests (von Piekartz et al 2019).

Bruxism is dominantly caused by increased jaw-muscle activity therefore muscle orientated treatments like stretching, trigger point treatment, dry needling will be have the best outcome

There is evidence that treating the source (masticatory) muscle influence function and reduce pain of the orofacial region (Vázquez Delgado et al 2010) but there is no clear outcome studies published on muscular treatment modalities in bruxism as defined in the INfORM consens group in 2013-2018. (Lobbezoo et al 2013-2018). Because myofascial TMD may be a risk factor for Bruxism, an increased nociception of the masticatory system may influence the intensity or frequency of bruxism but does not eliminate bruxism (A3 German Guideline Bruxism).
Reflecting on this information it may be concluded that bruxism in a complicated phenomenon which facilitates an interesting debate with many questions which can (still) not be answered. Bruxism seems to be the domain of the dentist because it has (also) to do with teeth. All credits on research, debates and consensus go to the dentist which is clearly fair but is it not also the domain of the psychology, somnology and physical therapy? There is the challenge for physical therapy. If physical therapy organizations and researcher execute studies specially on awake bruxism and also integrate and update knowledge in education for specialized physical therapy, for example the education CRAFTA provides, can we step on the exiting wave dentistry is on? The future will give us the answer.

Do you want to perform the first step? Read articles/guidelines the following for an excellent overview.

• Lobbezoo, F., Ahlberg, J., Raphael, K. G., Wetselaar, P., Glaros, A. G., Kato, T., ... & Koyano, K.(2018) International consensus on the assessment of bruxism: Report of a work in progress. Journal of oral rehabilitation, 45(11),837-844.
• German Society of Craniomandibular Function and Disorders (DGFDT),German Society of Dental, Oral and Craniomandibular Sciences (DGZMK) S3 Guideline (ect version) Bruxismus Diagnosis and Treatment, J. of Craniomand. Function (2019)11(3):225–i385(download https://www.dgfdt.de/aktuelles (Leitlinie Bruxismus) German and english

Harry von Piekartz

References

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2. Cesar, G. M., Tosato, P. J., & Biasotto-Gonzalez, D. A. (2006). Correlation between occlusion and cervical posture in patients with bruxism. Compendium of continuing education in dentistry (Jamesburg, NJ: 1995), 27(8), 463-6.
3. Ciancaglini, R., & Radaelli, G. (2001). The relationship between headache and symptoms of temporomandibular disorder in the general population. Journal of dentistry, 29(2), 93-98.
4. German Society of Craniomandibular Function and Disorders (DGFDT),German Society of Dental, Oral and Craniomandibular Sciences (DGZMK) S3 Guideline (ect version) Bruxismus Diagnosis and Treatment, J. of Craniomand. Function (2019)11(3):225–i385
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