A comparison of the masseteric silent period in temporomandibular joint dysfunction and normal human subjects by surface electromyography and single motor-unit recordings.
Single electric stimuli were delivered to the lower lip and the reflex effects were monitored in the ipsilateral masseter. Two strengths of stimulus were delivered at two levels of background excitation (defined in terms of the firing frequency of a single motor unit). Although the threshold stimulus intensity required to produce a silent period in the single motor units was the same for the patients with temporomandibular joint dysfunction and normal subjects, there were qualitative differences in the pattern of reflex responses between the two groups. Of the two phases of inhibition elicited by the stimulus, the short-latency inhibitory period was the more prominent and more resistant to changes in the background excitation levels in the dysfunction group. In normal subjects, however this was true of the long-latency inhibition. This difference may be due to the changes in the inputs to one or more of the interneurones linking the afferent limb of the reflex to the masseteric motoneurones.
Türker
K S
KS
Department of Physiology, University of Adelaide, SA, Australia.
Wilkinson
T M
TM
Miles
T S
TS
D000328:Adult; D001732:Bite Force; D004558:Electric Stimulation; D004576:Electromyography / Q000379:methods; D005071:Evoked Potentials; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008406:Masseter Muscle / Q000294:innervation / Q000503:physiopathology*; D008410:Masticatory Muscles / Q000503:physiopathology*; D009046:Motor Neurons / Q000502:physiology*; D011930:Reaction Time; D012018:Reflex / Q000502:physiology; D012684:Sensory Thresholds; D013706:Temporomandibular Joint Dysfunction Syndrome / Q000503:physiopathology*