Study to Probe Why Bruxism, Temporomandibular Disorders Appear to Be More Prevalent in PD

A new study may help investigators better understand the prevalence of bruxism and temporomandibular disorder (TMD) in patients with Parkinson disease (PD).

In study protocols published earlier this month, Merel Charlotte Verhoeff, MSc, of the Academic Center for Dentistry of Amsterdam, in the Netherlands, and colleagues, outlined the apparent association between bruxism, TMD, and PD, and explained how they hope their study will shed light on the issue.

Data collection on the study, which was delayed due to the COVID-19 pandemic, is set to take place between 2023 and 2025. The protocols were published in BMJ Open.

Patients with PD experience a range of symptoms, including motor symptoms like tremors and non-motor symptoms, like cognitive dysfunction, sleep problems, and pain. The disease is typically diagnosed when patients are in their 50s or 60s, but Verhoeff and colleagues noted that the aged population worldwide is increasing, suggesting that Parkinson’s might also increase in prevalence in the coming years. Oral health issues also tend to increase as patients age, and so the investigators said dentists may experience an increase in patients seeking assistance.

Bruxism—marked by repetitive clenching or grinding of the teeth or mandible—can eventually lead to mechanical tooth wear and TMD. However, Verhoeff and colleagues said these issues are not necessarily thought of as being associated with systemic disease.

“While oral health in PD has not been studied widely, oral (dys-)function in PD has been studied even less, even though PD, bruxism, and TMD have been suggested to share several common characteristics,” they said.

One of the few studies into the question was a recent study that compared 368 people with PD with 340 healthy controls suggested that the former group had higher rates of both bruxism and TMD, and that they experienced higher levels of pain with TMD compared to the controls. However, the investigators said both that study and one with similar findings from Taiwan had significant limitations. With the new study, Verhoeff and colleagues hope to more objectively investigate potential associations between PD, bruxism, and TMD, and better understand the role of factors such as disease severity and medication use. They also plan to assess tooth wear and saliva composition among patients with PD, the latter of which can contribute to tooth wear, they said.

The planned study will be a single-center study based on patients who visit an outpatient center for movement disorders. Though polysomnography is considered the gold standard in diagnosing bruxism, the study will instead use portable, single-channel electromyographic recorders at night and a mobile phone application to track daytime bruxism. These tools will make it feasible to track patients over several days, they said. The mobile phone application uses ecological momentary assessment, a system designed to maximize data validity by using real-time assessment of user behaviors. One limitation of the proposed study, however, is that it will not be able to distinguish between jaw-muscle activities caused by sleep bruxism, and those related to other disorders.

“This is an important issue, because such movement disorders can be present in patients with PD related to their medication usage,” Verhoeff and colleagues said, citing levodopa as one medication that can lead to a side effect that might emulate bruxism, oral dyskinesias.

The authors said they hope their research will generate stronger data about when and why bruxism and TMD occur in PD.

“Finally, more clinically relevant information will become available for dentists and other oral healthcare professionals about the amount of tooth wear and the composition of saliva in patients with PD,” they said.

Reference

Verhoeff MC, Koutris M, Berendse HW, van Dijk KD, Lobbezoo F. Parkinson's disease, temporomandibular disorder pain and bruxism and its clinical consequences: a protocol of a single-centre observational outpatient study. BMJ Open. Published online April 18, 2022. doi:10.1136/bmjopen-2021-052329