title: Effect of unilateral nasal obstruction on tongue protrusion forces in growing rats.
abstract: Mouth breathing caused by nasal obstruction affects the normal growth and development of craniofacial structures, including changes in the orofacial muscles. Tongue muscles play an important role in patency of the pharyngeal airway, and changes in the breathing pattern may influence tongue function. The purpose of this study was to evaluate the effect of unilateral nasal obstruction during growth on contractile properties of the tongue-protruding muscles. Sixty 6-day-old male Wistar albino rats were divided randomly into control (n = 30) and experimental (n = 30) groups. Rats in the experimental group underwent a unilateral nasal obstruction after cauterization of the external nostril at the age of 8 days, and muscle contractile characteristics were measured at 5, 7, and 9 wk of age. The specific parameters measured were twitch force, contraction time, half-decay time, tetanic force, and fatigue index. Repeated-measures multivariate analysis of variance was used for intergroup and intragroup statistical comparisons. Twitch contraction force and half-decay time were significantly increased in the experimental group at all ages. Tetanic forces at 60 and 80 Hz were significantly higher in the experimental group at all ages. The fatigue index was decreased significantly in the experimental group at the age of 5 wk. These results suggest that early unilateral nasal obstruction may increase the contraction force of the tongue-protruding muscles and prolong the duration of muscle contraction, which may influence the shape and development of the craniofacial complex.
authors.affiliation: Orthodontic Science, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan kuchima.orts@gmail.com.
authors.forename: Karin Harumi
authors.initials: KH
authors.lastname: Uchima Koecklin
authors.affiliation: Orthodontic Science, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Chiho
authors.initials: C
authors.lastname: Kato
authors.affiliation: Orthodontic Science, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Yukiha
authors.initials: Y
authors.lastname: Funaki
authors.affiliation: Orthodontic Science, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Maya
authors.initials: M
authors.lastname: Hiranuma
authors.affiliation: Orthodontic Science, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Ishida
authors.affiliation: Orthodontic Science, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Fujita
authors.affiliation: Orthodontic Science, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Tadachika
authors.initials: T
authors.lastname: Yabushita
authors.affiliation: Orthodontic Science, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kokai
authors.affiliation: Orthodontic Science, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ono
mesh_terms: D000818:Animals; D005221:Fatigue / Q000503:physiopathology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D015508:Nasal Obstruction / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D014059:Tongue / Q000503:physiopathology*
keywords: electric stimulation; hypoglossal nerve; mouth breathing; muscle contraction