Relationship between masseter muscle activity during wakefulness and temporomandibular disorder‐related symptoms

Abstract Background Masseter muscle activity during wakefulness may be associated with temporomandibular disorder (TMD)‐related symptoms, psychosocial status and pain‐related disability; however, this relationship is unclear. Objectives This study aimed to determine the relationship between masseter muscle electromyography (EMG) burst/duration during wakefulness and TMD‐related symptoms, psychosocial status and pain‐related disability. Methods Sixty participants were assessed masseter muscle activity during wakefulness using a data‐logger‐type ultraminiature EMG system and TMD‐related symptoms, psychosocial status and pain‐related disability through Axis I and II of the diagnostic criteria for TMD (DC/TMD). EMG bursts lasting longer than 0.25 s but less than 2.0 s and those lasting longer than 2.0 s were classified as phasic and tonic bursts, respectively. Results Participants with palpation‐related pain in the temporalis and masseter muscles, as assessed through the DC/TMD examination form in Axis I, had more bursts (number/h) ( p = .035 and p = .009, respectively) and longer duration (time/h) ( p = .013 and p = .004, respectively) of tonic bursts of the masseter muscle during wakefulness. Participants with palpation‐related pain in the masseter muscles had higher oral behaviour scores during wakefulness using Axis II ( p = .001), which affected the number and duration of tonic bursts of the masseter muscle activity during wakefulness ( p = .011 and p = .007, respectively). Conclusion As tonic bursts mainly reflect clenching, individuals with pain in the masseter muscles by palpation may have a high frequency and longer duration of clenching, as well as a high frequency of oral behaviours during wakefulness.