Abstract
Aim: This study aimed to investigate the association between masticatory muscle activity (MMA) during waketime and sleep time in adults reporting tooth clenching and/or grinding. It also investigated associations between MMA and tooth wear, masticatory muscle pain, as well as self-reported stress and anxiety.
Methods: Study participants were screened via an e-mail survey using the oral behaviours checklist. Respondents were recruited sequentially starting with those with the highest score. The final sample consisted of 30 individuals, whose MMA was recorded over two to three days in the free environment using a wearable electromyography (EMG) device, including both waketime and sleeping. Digital intraoral scans and intraoral photographs were used to compute tooth wear using a standardised index, and stress and anxiety levels were recorded using validated questionnaires. A report of masticatory muscle pain was also registered. Results were analysed using descriptive statistics and linear mixed modelling.
Results: Significant correlations were found between mean waketime and sleep time contraction episode frequency, duty time and amount of rhythmic MMA (p < 0.023). These correlations remained strong after adjusting in a multivariate analysis. No correlations were observed between mean duration and mean amplitude of contraction episodes. A significant association was observed between mean contraction episode frequency during sleep and tooth wear, however this was no longer significant after adjusting for age and sex in a multivariate model. Sleep time rhythmic MMA and a report of masticatory muscle pain were positively associated, however no associations were observed between MMA and self- reported stress or anxiety, either while asleep or while awake.
Conclusions: Waketime and sleep time MMA were associated, which challenges to notion that sleep bruxism and awake bruxism are completely separate conditions. Rhythmic MMA during sleep may be involved in the aetiology of masticatory muscle pain. The multifactorial nature of tooth wear means that using it to diagnose bruxism may be misleading.