Electromyographic correlates of common oral behaviors

Objective: The assessment of oral parafunctional behaviors, as one source of muscle overuse possibly related to TMD, remains complex due to inaccuracies of self-report. We developed the Oral Behaviors Checklist (Ohrbach et al, 2004) as a comprehensive self-report instrument for such behaviors; the present study investigates electromyographic equivalents of those behaviors by contrasting cases vs controls in terms of resting performance, the semantics and physiological equivalents of one common behavior (tooth clenching) and comparison of oral behaviors to non-oral behaviors for generalizability. Methods: Surface EMG was used to measure masseter, temporalis, and suprahyoid muscles (oral behaviors) as well as biceps muscles (non-oral behaviors) in 11 controls and 13 TMD cases. Subjects were instructed to perform specific behaviors, EMG was obtained during two sequential trials with baseline trials intervening, and data were reduced and analyzed off-line. Results: Cases and controls each exhibited similar types of patterning (linear vs non-linear) in lifting weights with their arm (?2, p =0.86) and baseline values between trials exhibited high variability in both groups. Both groups exhibited very high variability in masticatory muscle baselines, with TMD slightly greater than controls averaged over 17 separate baseline trials (non-significant); best baseline values demonstrated that TMD exhibited marginally higher resting EMG vs controls (t-test, avg p=0.062). The EMG of 4 similar behaviors (clench, touch, press, hold) was different (ANOVA, p = 0.013) but the groups did not differ within behavior. Conclusion: These data demonstrate within-subject and between-group differences in organization of motor control for simple tasks. TMD subjects appear to generate higher levels of resting EMG. Similar oral behaviors have distinctive and widely understood electrophysiology associated with the semantics of those behaviors. Research supported by NIH DE-13221 and T-35 DE-07106.