title: [Relationship between mechanical stimulation to the teeth and sternocleidomastoid muscle activities in human].
abstract: Concomitant head and mandibular movements in mastication are thought to be regulated by sensory inputs to the stomatognathic receptors. In rats, a reflex pathway from the periodontal mechanoreceptors to the neck muscles has been reported. However, no such pathway has been found in humans. The aim of this study was to find whether pressure stimulation to the teeth influences neck muscles in humans. The subjects were 8 healthy adults who were asked to sit in a chair with a backrest and a headrest so that the head was fixed. The upper right canine was subject to pressure by an electrical-powered stimulator in a posterior-anterior direction. The pressure was applied in a ramp-and-hold stimulation. Maximal continuous loading was 2 N with a ramp speed of 4 N/s and the stimulation interval was 5 s. The motor unit activities of the right sternocleidomastoid muscle (SCM) were recorded by needle electromyogram and analyzed as instantaneous frequency. As a result, instantaneous frequencies of activity of all 14 motor units significantly increased from 11.8 +/- 1.4 Hz before stimulation to 15.4 +/- 1.5 Hz during stimulation (p < 0.01). This result suggests that pressure stimulation to teeth induced the tonic discharge of the SCM. Therefore, there is a functional relationship between the teeth and neck muscles in humans.
authors.affiliation: Orthodontic Science, Department of Orofacial Development and Function, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University.
authors.forename: Takashi
authors.initials: T
authors.lastname: Momozawa
mesh_terms: D000328:Adult; D004576:Electromyography; D006801:Humans; D008297:Male; D008409:Mastication / Q000502:physiology; D008465:Mechanoreceptors / Q000502:physiology*; D009334:Neck Muscles / Q000502:physiology*; D010812:Physical Stimulation; D011312:Pressure; D013314:Stress, Mechanical; D014070:Tooth / Q000502:physiology*