title: Effects of increased occlusal vertical dimension on the jaw-opening reflex in adult rats.
abstract: OBJECTIVE
  Malocclusion with deep overbite and facial esthetics improve when facial height is intentionally increased during orthodontic extrusion of the posterior teeth. Thus, a better understanding of post-treatment stability of increased occlusal vertical dimension (iOVD) in adult patients is important. We focused on the jaw-opening reflex (JOR), which plays an important role in the control of jaw movements during mastication, and investigated the effects of iOVD on the JOR in rats with an electrophysiological technique.
  
  
  METHODS
  One hundred and twenty 13-week-old male Wistar rats were randomly divided into control and experimental groups. Rats in the experimental group received a 2-mm buildup of composite resin on the maxillary molars at 13 weeks of age. The JOR was induced by low-intensity electrical stimulation of the left inferior alveolar nerve. The electromyographic responses were recorded from the digastric muscle at 13, 14, 15, 17, 19, and 23 weeks of age. JOR properties including latency, duration, and peak-to-peak amplitude were measured and compared between the groups.
  
  
  RESULTS
  The latency of the JOR was significantly longer and the peak-to-peak amplitude was significantly smaller in the experimental group than in the control group from 14 to 19 weeks of age, while the reflex duration was not significantly different. Intra-group comparisons of the latency and peak-to-peak amplitudes among rats 14-19 weeks of age were significantly different between the experimental group and the control group.
  
  
  CONCLUSIONS
  iOVD affected the latency and amplitude of the JOR but not the duration. The JOR adapted after 10 weeks of iOVD.
authors.affiliation: Orthodontic Science, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
authors.forename: Mio
authors.initials: M
authors.lastname: Makiguchi
authors.affiliation: Orthodontic Science, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, 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, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, 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, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
authors.forename: Hidemasa
authors.initials: H
authors.lastname: Okihara
authors.affiliation: Orthodontic Science, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, 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, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, 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, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan. Electronic address: skokai.orts@tmd.ac.jp.
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, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ono
mesh_terms: D000818:Animals; D004576:Electromyography; D007568:Jaw / Q000502:physiology*; D008297:Male; D008409:Mastication / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012018:Reflex / Q000502:physiology*; D014716:Vertical Dimension
keywords: Jaw-opening reflex; Occlusal vertical dimension; Rat