title: Changes in the temporomandibular joint disc position after orthognathic surgery.
abstract: OBJECTIVE
  This clinical research was carried out to investigate the influences of orthognathic surgery on the temporomandibular joint (TMJ) using magnetic resonance imaging (MRI) taken before and after the surgery.
  
  
  METHODS
  There were 23 subjects who had a bilateral sagittal split ramus osteotomy in Seoul National University Bundang Hospital from June 2004 to December 2006 and their condyles. The mean age of patients was 22.09 +/- 3.65 and the number of men and women was 10 and 13, respectively. Bilateral sagittal planes of 46 condyles had taken MRI in both closed and open mouth states before and 3 months after surgery. The differences between pre- and postoperative disc positions and internal disc derangement (IDD) stages were evaluated. Furthermore, a correlation analysis of the amounts of mandibular set-back and disc positions was carried out. Paired-samples of the T tests, the McNemar-Bowker test and Pearson correlation analysis were applied as statistical methods. In this study, a significance level is considered to be less than 0.05.
  
  
  RESULTS
  The disc positions had not shown statistically significant differences between pre- and post-operation in the closed state. However there were significant increases of distances between the discs and condyle on mouth opening. For instance, 0.70 +/- 1.30 mm was an average (P < .01). The derangement stages of each condyle were not changed through the operation. Although there were improved or aggravated cases, the orthognathic surgery had no influence on derangement stages in this study. Last, there was no significant correlation between the 2 variables of the amounts of set-back and the changes of disc position.
  
  
  CONCLUSIONS
  Although there were significant differences of the disc positions in the open mouth state, the orthognathic surgery appears not to have had an effect on the TMJ.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Seoul National University Bundang Hospital, Seoul, Republic of Korea.
authors.forename: Young-Kyun
authors.initials: YK
authors.lastname: Kim
authors.forename: Pil-Young
authors.initials: PY
authors.lastname: Yun
authors.forename: Ji-Yeon
authors.initials: JY
authors.lastname: Ahn
authors.forename: Jong-Wan
authors.initials: JW
authors.lastname: Kim
authors.forename: Su-Gwan
authors.initials: SG
authors.lastname: Kim
mesh_terms: D020341:Absorbable Implants; D001860:Bone Plates; D001863:Bone Screws; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D004204:Joint Dislocations / Q000175:diagnosis; D008279:Magnetic Resonance Imaging; D008297:Male; D008334:Mandible / Q000601:surgery*; D008335:Mandibular Condyle / Q000473:pathology; D010027:Osteotomy / Q000295:instrumentation / Q000379:methods*; D011378:Prognathism / Q000601:surgery; D016059:Range of Motion, Articular / Q000502:physiology; D013701:Temporal Bone / Q000473:pathology; D013704:Temporomandibular Joint / Q000473:pathology; D019224:Temporomandibular Joint Disc / Q000473:pathology*; D055815:Young Adult