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

Structured Abstract ObjectiveTo determine differences in masticatory muscle usage between temporomandibular joint disorders diagnostic groups. Setting and sample populationSeventy-one informed and consented subjects (27 men; 44 women) participated at the University at Buffalo. Material and methodsResearch 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 20N bite-force (T-20N, V). Over 3days 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% T-20N). anova and Tukey-Kramer post hoc tests identified 1) diagnostic group differences in T-20N and 2) the effects of diagnostic group, gender, time and interval on muscle DFs. ResultsMean (SE) temporalis T-20N in +DD+P subjects was significantly higher (71.4 +/- 8.8V) than masseter T-20N in these subjects (19.6 +/- 8.8V; p=0.001) and in -DD-P subjects (25.3 +/- 6.0V, p=0.0007). Masseter DFs at 5-9% T-20N 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<0.03), and in +DD+P women (2.00%) compared to -DD-P men (0.83%; p=0.029). Night-time DFs at 5-9% T-20N in +DD-P women (1.97%) were significantly higher than in -DD-P men (0.47%) and women (0.24%; all p<0.01). ConclusionsBetween-group differences were found in masticatory muscle activities in both laboratory and natural environmental settings.