The intensity of awake bruxism episodes is increased in individuals with high trait anxiety

Objectives Trait anxiety is associated with an increased occurrence of awake bruxism episodes, a behavior characterized by clenching of the teeth contributing to temporomandibular disorders in some individuals. Here we measured the activity of the masseter and the intensity and duration of spontaneous wake-time tooth clenching episodes in healthy individuals with different levels of trait anxiety (TA). Materials and methods Two hundred fifty-five individuals completed a web survey. Using their TA scores, we allocated them in low (< 20 th percentile of the TA score distribution), intermediate (between 20 th and 80 th ), and high (> 80 th ) TA groups. We analyzed the electromyographic (EMG) activity of the right masseter during a 15-min silent reading task in forty-three individuals with low ( n = 12), intermediate ( n = 17), and high TA ( n = 14). We tested between-group differences in EMG activity of the masseter, as well as postural activity—the muscular activity that maintains mandibular posture, and amplitude and duration of spontaneous tooth clenching episodes. Results The activity of the masseter (mean ± SEM %maximum voluntary contraction/MVC) was greater in the high TA (10.23 ± 0.16%MVC) than the intermediate (8.49 ± 0.16%MVC) and low (7.97 ± 0.22%MVC) TA groups (all p < 0.001). Postural activity did not differ between groups (all p > 0.05). The EMG amplitude of tooth clenching episodes was greater in the high TA (19.97 ± 0.21 %MVC) than the intermediate (16.40 ± 0.24%MVC) and low (15.48 ± 0.38 %MVC) TA groups (all p < 0.05). The cumulative duration of clenching episodes was not different between groups ( p = 0.390). Conclusions Increased TA is associated with both increased masseter muscle activity and intensity of wake-time tooth clenching episodes. Clinical relevance TA may contribute significantly to masticatory muscle overload.