Mindfulness Level Influences the Frequency, Amplitude and Duration of Awake Bruxism Episodes During Standardised Mental Capacity Tasks

Abstract

Background: Awake bruxism (AB) is characterised by repetitive or sustained masticatory muscle activity during wakefulness, including clenching, grinding, or mandibular bracing. Recent consensus defines AB as a motor behaviour influenced by psychological and contextual factors. Among these, dispositional mindfulness may play a modulatory role in the frequency and intensity of AB episodes.

Objective: This study aimed to evaluate how standardised cognitive tasks of varying complexity modulate awake bruxism (AB) and to investigate whether dispositional mindfulness is associated with the frequency, duration, and amplitude of AB episodes measured by surface electromyography.

Methods: A cross-sectional study was conducted with 68 dental students (18-40 years) from the School of Dentistry of Ribeirão Preto, University of São Paulo. Participants were classified into AB and control groups based on self-report and Ecological Momentary Assessment (EMA). Surface electromyography (sEMG) of the masseter muscle was recorded during five conditions: rest, maximal voluntary clenching, self-report questionnaires, mathematical tasks of different complexity, and an electronic memory game (Genius). Episodes were analysed at thresholds of 10%, 20%, and 30% of maximal voluntary contraction (Ap10, Ap20, Ap30), extracting frequency, duration, and amplitude. Dispositional mindfulness was assessed using the Five Facet Mindfulness Questionnaire (FFMQ). Statistical analyses included Friedman tests, Mann-Whitney U tests, Generalised Estimating Equations (GEE), and Spearman correlations.

Results: Controls showed increased episode frequency at lower thresholds (Ap10) as task complexity rose, whereas AB individuals maintained elevated frequencies across all tasks. Significant between-group differences were observed at higher thresholds (Ap20, Ap30). Duration and amplitude showed no significant differences, except for a trend of greater amplitude in controls during the Genius task. Within the AB group, higher dispositional mindfulness was associated with fewer and shorter contraction episodes, a pattern consistent with previous research indicating a potential protective association. (notably at Ap30) and shorter durations across tasks, while no associations were observed in controls.

Conclusion: AB individuals exhibited a stable and persistent pattern of masticatory muscle activity, contrasting with the adaptive modulation observed in controls. Higher dispositional mindfulness was linked to fewer and shorter contraction episodes in the AB group, suggesting a protective role. These findings highlight the relevance of integrating psychological traits, such as mindfulness, into the behavioural understanding and management of AB.

Keywords: awake bruxism; cognitive tasks; five facet mindfulness questionnaire; mindfulness; surface electromyography.