Day-To-Day Variation in Masseteric Electromyographic Waveforms During the Diurnal Awake State

To establish diagnostic/assessment criteria for awake bruxism (AB) using electromyography of the masseter muscle during the diurnal awake state (d-EMG), it is necessary to refer to the actual state of variation of d-EMG waveforms between different days (d-variation).

This study aimed to clarify the actual state of d-variation in various indices of d-EMG waveforms.

The participants included 91 volunteers with or without awareness of diurnal tooth clenching. Measurements were conducted on three days within a two-week period using a wearable EMG device set at the unilateral masseteric region. A waveform with an amplitude more than twice the baseline and a duration of more than 0.25 s was defined as a burst. The number of bursts/h, number of episodes/h, number of bursts ≥ 20% maximum voluntary clenching (MVC)/h, burst integral value/h, and standardised burst integral value/h were calculated. The coefficient of variation (CV) of the three measurement days was calculated for each index.

The five indices showed no significant differences among the three days. The median CV for the number of episodes/h, number of bursts/h, number of bursts ≥ 20% MVC/h, burst integral value/h, and standardised burst integral value/h were 0.233, 0.276, 0.507, 0.417, and 0.482, respectively. Of the indices, bursts/h and episodes/h had the smallest day-to-day variation. The CV for the number of waveforms tended to be smaller the larger the number of waveforms.

These findings are considered useful as reference data for establishing diagnostic/assessment criteria for AB using masseter EMG in the future.