title: Relationship between Class III malocclusion and hyoid bone displacement during swallowing: a cine-magnetic resonance imaging study.
abstract: OBJECTIVE
  The displacement of the hyoid bone (HB) is a critical biomechanical component of the swallowing function. The aim of this study was to evaluate the swallowing-induced vertical and horizontal displacements of the HB in subjects with 2 different magnitudes of skeletal Class III malocclusion, by means of real-time, balanced turbo-field-echo (B-TFE) cine-magnetic resonance imaging.
  
  
  METHODS
  The study population comprised 19 patients with mild skeletal Class III malocclusion, 16 with severe skeletal Class III malocclusion, and 20 with a skeletal Class I relationship. Before the commencement of the study, all subjects underwent cephalometric analysis to identify the nature of skeletal malformations. B-TFE images were obtained for the 4 consecutive stages of deglutition as each patient swallowed 10 mL of water, and the vertical and horizontal displacements of the HB were measured at each stage.
  
  
  RESULTS
  At all stages of swallowing, the vertical position of the HB in the severe Class III malocclusion group was significantly lower than those in the mild Class III and Class I malocclusion groups. Similarly, the horizontal displacement of the HB was found to be significantly associated with the severity of malocclusion, i.e., the degree of Class III malocclusion, while the amount of anterior displacement of the HB decreased with an increase in the severity of the Class III deformity.
  
  
  CONCLUSIONS
  Our findings indicate the existence of a relationship between the magnitude of Class III malocclusion and HB displacement during swallowing.
authors.affiliation: Department of Orthodontics, Dental Science Center, Gulhane Military Medical Academy, Ankara, Turkey.
authors.forename: Sila Mermut
authors.initials: SM
authors.lastname: Gokce
authors.forename: Hasan Suat
authors.initials: HS
authors.lastname: Gokce
authors.forename: Serkan
authors.initials: S
authors.lastname: Gorgulu
authors.forename: Seniz
authors.initials: S
authors.lastname: Karacay
authors.forename: Eralp
authors.initials: E
authors.lastname: Akca
authors.forename: Huseyin
authors.initials: H
authors.lastname: Olmez
keywords: Class III malocclusion; Deglutition; Hyoid bone; Magnetic resonance imaging; Swallowing