• Osamu Komiyama, Kelun Wang, Peter Svensson, Lars Arendt-Nielsen, Misao Kawara, and Antoon De Laat.
• Department of Clinical Oral Physiology, Nihon University School of Dentistry at Matsudo, 2-870-1 Sakaecho-nishi, Matsudo, Chiba 271-8587, Japan. komiyama.osamu@nihon-u.ac.jp
• Clin Neurophysiol. 2009 Feb 1;120(2):384-9.

ObjectiveThe present study evaluated ethnic differences in sensory, pain responses, and the exteroceptive suppression reflex (ES) in the trigeminal region.MethodsTwenty-eight Caucasian (14 men and 14 women, age from 20 to 31) and 28 gender and age matched Japanese participated. Tactile detection thresholds and filament-prick pain detection thresholds were measured on the left cheek skin. Surface EMG was recorded from the left masseter muscle, and 13 different intensities of electrical stimuli were applied to the skin overlying the left mental nerve. The first stimulation intensity at which the late ES appeared was defined as the electrical reflex threshold. The duration and suppression degree of the ES were also determined.ResultsJapanese subjects had a significantly lower sensory and pain threshold then Caucasian subjects. Caucasian subjects had a significantly lower electrical reflex threshold in comparison to Japanese subjects. Caucasian subjects had significantly longer duration of the ES and larger suppression degree of the ES compared to Japanese subjects.ConclusionsOur results demonstrate that ethnic differences exist not only concerning sensory and pain responses but also regarding reflex (motor) responses.SignificanceThe findings of this study have direct implications for studies evaluating different types of orofacial pain conditions and trigeminal reflexes.

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