A pilot study of ambulatory masticatory muscle activities in temporomandibular joint disorders diagnostic groups

Structured Objective To determine differences in masticatory muscle usage between temporomandibular joint disorders diagnostic groups. Setting and sample population Seventy‐one informed and consented subjects (27 men; 44 women) participated at the University at Buffalo. Material and methods Research diagnostic criteria and imaging data were used to categorize subjects according to the presence/absence (+/−) of TMJ disc placement (DD) and chronic pain (P) (+DD+P, n = 18; +DD−P, n = 14; −DD−P, n = 39). Electromyographic (EMG)/bite‐force calibrations determined subject‐specific masseter and temporalis muscle activities per 20 N bite‐force (T20N, μV). Over 3 days and nights, subjects collected EMG recordings. Duty factors (DFs, % of recording time) were determined based on threshold intervals (5–9, 10–24, 25–49, 50–79, ≥80% T20N). anova and Tukey–Kramer post hoc tests identified 1) diagnostic group differences in T20N and 2) the effects of diagnostic group, gender, time and interval on muscle DFs. Results Mean (± SE) temporalis T20N in +DD+P subjects was significantly higher (71.4 ± 8.8 μV) than masseter T20N in these subjects (19.6 ± 8.8 μV; p = 0.001) and in −DD−P subjects (25.3 ± 6.0 μV, p = 0.0007). Masseter DFs at 5–9% T20N were significantly higher in +DD−P women (3.48%) than +DD−P men (0.85%) and women and men in both other diagnostic groups (all p