Magnetic and electric stimulation to elicit the masseteric exteroceptive suppression period

OBJECTIVES: The present study compared the perception of electric and magnetic stimuli for reflex appearance threshold (RT) and reflex saturation threshold (RS) of the exteroceptive suppression reflex (ES) in the masseter muscle. METHODS: Twelve healthy males and 12 females (age: 24.2+/-3.2 years) participated. The surface EMG was recorded from the left masseter muscle. The stimulus intensities were set as multiple values of the sensory threshold (ST), and were applied to the skin above the left mental nerve. Subjects reported the perceived intensity of the stimulus on a numeric rating scale (NRS) at RT and RS for the early and late ES (ES1 and ES2, respectively). RESULTS: ES2 had a lower RT and RS compared to ES1 in electric and magnetic stimulation. Significantly lower NRS values at RT and RS were found with painless magnetic stimulation compared to electric stimulation (p<0.01). CONCLUSIONS: In contrast to electrical stimulation, both ES1 and ES2 appeared and saturated with painless magnetic stimuli. SIGNIFICANCE: The present results indicate that both ES1 and ES2 have a non-nociceptive origin. Painless magnetic stimuli will be an advantage in ES reflex examinations for various orofacial pain conditions.