title: Evaluation of upper airway obstruction in Class II children with fluid-mechanical simulation.
abstract: BACKGROUND
  The purpose of this study was to test the null hypothesis that dolichofacial and brachyfacial children with Class II malocclusion do not differ in upper airway obstruction. Furthermore, the ability of fluid-mechanical simulation to detect airway obstruction within the limitations of simulation was examined.
  
  
  METHODS
  Forty subjects from 7 to 11 years of age with Class II malocclusion participated and were divided into 2 groups, dolichofacial and brachyfacial, based on their Frankfort mandibular plane angles. Cone-beam computed tomography images supplied the shape of the entire airway. Two measures of respiratory function, air velocity and pressure, were simulated by using 3-dimensional images of the airway. The images and simulations were compared between the 2 facial types.
  
  
  RESULTS
  The size of the upper airway did not differ statistically between facial types; however, the simulated maximal pressure and velocity of the dolichofacial type were significantly higher than those of the brachyfacial type.
  
  
  CONCLUSIONS
  Airway obstruction differs with the Frankfort mandibular plane angle, even though the depth and cross-sectional area of the airway do not. The fluid-mechanical simulation system developed in this study detected differences in airway obstruction that were not apparent from morphologic studies.
authors.affiliation: Developmental Medicine, Health Research Course, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan. yamame@dent.kagoshima-u.ac.jp
authors.forename: Tomonori
authors.initials: T
authors.lastname: Iwasaki
authors.forename: Issei
authors.initials: I
authors.lastname: Saitoh
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Takemoto
authors.forename: Emi
authors.initials: E
authors.lastname: Inada
authors.forename: Ryuzo
authors.initials: R
authors.lastname: Kanomi
authors.forename: Haruaki
authors.initials: H
authors.lastname: Hayasaki
authors.forename: Youichi
authors.initials: Y
authors.lastname: Yamasaki
mesh_terms: D000402:Airway Obstruction / Q000000981:diagnostic imaging / Q000503:physiopathology*; D000403:Airway Resistance; D019412:Anatomy, Cross-Sectional; D002508:Cephalometry; D002648:Child; D003198:Computer Simulation; D054893:Cone-Beam Computed Tomography; D005145:Face / Q000033:anatomy & histology*; D006801:Humans; D057446:Hydrodynamics; D021621:Imaging, Three-Dimensional; D008312:Malocclusion, Angle Class II / Q000150:complications*; D008445:Maxillofacial Development; D009058:Mouth Breathing / Q000503:physiopathology; D009296:Nasal Cavity / Q000503:physiopathology*; D015588:Observer Variation; D010614:Pharynx / Q000473:pathology / Q000503:physiopathology*; D011312:Pressure; D012123:Pulmonary Ventilation; D018709:Statistics, Nonparametric; D014716:Vertical Dimension