Investigation of the effect of Bruxism on masticatory muscle activity, muscle mechani̇cal properties, and pressure pain threshold in individuals with temporomandibular joint dysfunction

This study aimed to compare the relationships between masticatory muscle activity, mechanical properties of orofacial muscles, pressure pain threshold, oral parafunctional behaviors, depression, anxiety, and pain intensity in individuals with temporomandibular joint dysfunction (TMD) who have bruxism and those without bruxism. A total of 83 individuals with TMJOD (45 with bruxism, 38 without bruxism) were evaluated. TMD severity was assessed using the Fonseca Anamnestic Index (FAI), the presence of bruxism was based on self-report, muscle activity was measured using surface electromyography, muscle mechanical properties were measured using a myotonometer, pressure pain threshold was measured using an algometer, parafunctional behaviors were assessed using the Oral Habits Checklist, depression level was measured using the Patient Health Questionnaire – 4, anxiety level with the Generalized Anxiety Disorder Scale, and pain intensity with the Chronic Pain Rating Scale. Measurements were taken on the same day and at specific rest intervals. In the bruxism group, TMED severity (p<0.001), pressure pain threshold in the masseter (p=0.041) and anterior temporalis (p=0.046) muscles, parafunctional behaviors (p=0.002), anxiety (p=0.003), and depression (p=0.006) scores were higher. In the bruxism group, the elasticity of the masseter (p=0.003) and SKM (p=0.022) muscles was higher. In non-bruxers, the fatigue value of the right masseter muscle (p=0.043) and the muscle's activity onset frequency value (p=0.011) were higher. In non-bruxers, masseter muscle tone (p=0.012) and stiffness (p=0.002) were higher. Elasticity of the anterior temporalis muscle was also higher in the non-bruxer group (p=0.010). Maximum voluntary muscle contraction values were similar between groups (p>0.05). The findings suggest that bruxism may affect jaw function and psychological status in individuals with TMD, contributing to the understanding of the multifactorial nature of TMD.