title: Are Hyoid Bone and Tongue the Risk Factors Contributing to Postoperative Relapse for Mandibular Prognathism?
abstract: OBJECTIVE
  The purpose of this study was to investigate postoperative stability and the correlation between hyoid, tongue, and mandible position following surgery for mandibular prognathism.
  
  
  METHODS
  Thirty-seven patients, treated for mandibular prognathism using intraoral vertical ramus osteotomy (IVRO), were evaluated cephalometrically. A set of four standardized lateral cephalograms were obtained from each subject preoperatively (T1), immediately postoperatively (T2), six weeks to three months postoperatively (T3), and more than one year postoperatively (T4). The Student t-tests, the Pearson correlation coefficient, and the multiple linear regression were used for statistical analysis.
  
  
  RESULTS
  Immediately after surgery, menton (Me) setback was 12.8 mm, hyoid (H) setback was 4.9 mm, and vallecula epiglottica (V) setback was 5.8 mm. The postoperative stability significantly correlated (r = -0.512, p < 0.01) with the amount of setback. The hyoid bone and tongue did not have significant effects on postoperative stability. Multiple linear regression model (R(2) = 0.2658, p < 0.05) showed predictability: Horizontal Relapse Me (T4-T2) = -6.406 - 0.488Me (T2-T1) + 0.069H (T2-T1) - 0.0619V (T2-T1).
  
  
  CONCLUSIONS
  Mandibular setback surgery may push the hyoid and tongue significantly backward, but this did not correlate with mandibular relapse. Postoperative stability significantly correlated with the amount of mandibular setback.
authors.affiliation: Graduate Institute of Dental Sciences, College of Dental Medicine, Kaohsiung Medical University, No. 100, Shih-Chuan 1st Road, Kaohsiung 807, Taiwan; Department of Orthodontics, Kaohsiung Medical University Hospital, No. 100, Shih-Chuan 1st Road, Kaohsiung 807, Taiwan.
authors.forename: Yu-Chuan
authors.initials: YC
authors.lastname: Tseng
authors.affiliation: Department of Oral and Maxillofacial Surgery, Kaohsiung Medical University Hospital, No. 100, Shih-Chuan 1st Road, Kaohsiung 807, Taiwan.
authors.forename: Steven
authors.initials: S
authors.lastname: Lai
authors.affiliation: Graduate Institute of Dental Sciences, College of Dental Medicine, Kaohsiung Medical University, No. 100, Shih-Chuan 1st Road, Kaohsiung 807, Taiwan.
authors.forename: Huey-Er
authors.initials: HE
authors.lastname: Lee
authors.affiliation: Graduate Institute of Dental Sciences, College of Dental Medicine, Kaohsiung Medical University, No. 100, Shih-Chuan 1st Road, Kaohsiung 807, Taiwan.
authors.forename: Ker-Kong
authors.initials: KK
authors.lastname: Chen
authors.affiliation: Department of Oral and Maxillofacial Surgery, Kaohsiung Medical University Hospital, No. 100, Shih-Chuan 1st Road, Kaohsiung 807, Taiwan.
authors.forename: Chun-Ming
authors.initials: CM
authors.lastname: Chen
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D006928:Hyoid Bone / Q000473:pathology / Q000601:surgery*; D008297:Male; D008313:Malocclusion, Angle Class III / Q000473:pathology / Q000601:surgery*; D008334:Mandible / Q000473:pathology / Q000601:surgery*; D008875:Middle Aged; D011184:Postoperative Period; D012307:Risk Factors; D014059:Tongue / Q000473:pathology / Q000601:surgery*