Whether sleep bruxism is primary or secondary has implications on disorder management.

By Sree Roy

Sleep bruxism (SB) prevalence is higher in patients with obstructive sleep apnea (OSA) than in those without the sleep disorder—which some investigators hypothesize is because the rhythmic masticatory muscle activity may help to restore a compromised upper airway during respiratory events. But PhD candidate Boyuan Kuang thought that hypothesis could be incorrect: He suspected that the contractions of the jaw-closing muscles that occur shortly after respiratory events during sleep are instead simply non-specific orofacial activities (such as swallowing and lip movement) dependent on the arousal response rather than on the respiratory events per se.

As part of his PhD thesis, Kuang has been investigating the associations between sleep bruxism and other sleep-related disorders, and this newly published abstract is one of the focal points of his PhD research. The American Academy of Dental Sleep Medicine (AADSM) awarded it a Student Excellence Award for 2020 and published it in the April 2020 edition of the Journal of Dental Sleep Medicine.

The 221-participant polysomnography study found the jaw-closing muscle activity shortly after respiratory events in OSA patients to be a non-specific orofacial activity—not related to sleep bruxism. There was a significant correlation between non-specific orofacial activities index and respiratory arousal index (r=0.376, P< 0.001), but no significant correlation between rhythmic masticatory muscle activity index and respiratory arousal index (r=0.079, P=0.245).

“Insight into the underlying mechanisms of these relationships may assist the clinician in making a distinction between the primary [idiopathic] and secondary [associated with a medical condition] forms of sleep bruxism….The distinction between these two forms is important, as the management may be distinct,” says Kuang, who is affiliated with Academic Centre for Dentistry Amsterdam, University of Amsterdam, and Vrije Universiteit Amsterdam, all in The Netherlands. “In cases where the primary form of SB has harmful consequences (eg, breaking or losing teeth, fillings, or implants; wear of the teeth; musculoskeletal pain; and mandibular dysfunction complaints), management of sleep bruxism is often necessary. However, when SB is a comorbid condition of other sleep-related disorders, management of the associated medical conditions by an expert physician should be the focus.

“In this large-scale polysomnographic study, we found that sleep bruxism and OSA are associated with sleep arousals. The likelihood of arousals potentially influences the probability of SB occurrence in OSA patients. Management of secondary SB with negative health consequences in OSA patients should therefore be done in collaboration with sleep medicine physicians.”

The China Scholarship Council provided financial support for this research.

Sree Roy is editor of Sleep Review.


Kuang B, Li D, Lobbezoo F, et al. A large-scale polysomnographic study on the associations between masticatory muscle activity and arousals in OSA patients. JDSM. 10 Apr 2020;7.2: Abstract #003.