title: Relationship between stage II transport and number of chewing strokes as mastication progresses.
abstract: As mastication progresses, little is known about the occurrence of the stage II transport (oro-pharyngeal bolus transport). This study aimed to investigate the relationship between stage II transport and bolus aggregation in the pharynx and the number of chewing strokes. Twenty-five clinical residents with natural dentitions were recruited. The subjects were asked to chew gummy jelly with their preferred rhythm and to swallow the bolus at their preferred timing. To investigate stage II transport and bolus aggregation in the pharynx, a transnasal endoscope was used. The number of chewing strokes was measured by electromyographic activity from the masseter muscle. The mean numbers of chewing strokes of pre-stage II transport and post-stage II transport were 29.8 and 8.1, respectively; the difference was significant (p<0.01). The ratio of the number of chewing strokes of pre-stage II transport to that of post-stage II transport was 4.0 to 1.0. This study showed that stage II transport started at four-fifths of the way along the progress of mastication, and that stage II transport and bolus aggregation in the pharynx are related to the number of chewing strokes.
authors.affiliation: Department of Clinical Oral Health Science, Tokyo Dental College, 2-9-18 Misakicho, Chiyoda, Tokyo 101-0061, Japan. Electronic address: syamashita@tdc.ac.jp.
authors.forename: Shuichiro
authors.initials: S
authors.lastname: Yamashita
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sugita
authors.forename: Koichiro
authors.initials: K
authors.lastname: Matsuo
mesh_terms: D000328:Adult; D003679:Deglutition / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000502:physiology*; D008409:Mastication / Q000502:physiology*; D010614:Pharynx / Q000502:physiology
keywords: EMG; Mastication; Stage II transport; Swallowing; Transnasal endoscope