title: Adaptation of jaw closing muscles after surgical mandibular advancement procedures in different vertical craniofacial types: a magnetic resonance imaging study.
abstract: OBJECTIVE
  Surgical mandibular advancement influences the biomechanics of the mandible and as a result may provoke relapse. In this study, the adaptation of the masseter (MAS) and medial pterygoid muscles (MPM) after surgical mandibular advancement was evaluated.
  
  
  METHODS
  Of 12 patients with mandibular retrognathia and varying vertical craniofacial morphology, axial and 30 degrees angulated magnetic resonance imaging (MRI) scan series were taken preoperatively and 10 to 48 months postoperatively. Using cluster analysis, subjects were assigned to a long-face (LF) and a short-face (SF) cluster. Subsequently, preoperative and postoperative maximum cross-sectional areas and volumes of the MAS and MPM were compared in these groups.
  
  
  RESULTS
  The cross-sectional area and volume of the MAS decreased significantly in both the SF and LF cluster (up to 18%). Although not significantly, this phenomenon tended to be more pronounced in LF patients. The cross-sectional area of the MPM showed less adaptation.
  
  
  CONCLUSIONS
  The jaw-closing muscles become significantly smaller after surgical mandibular advancement, irrespective of the vertical craniofacial type.
authors.affiliation: Department of Oral and Maxillofacial Surgery/Pathology, ACTA and VU University Medical Center, Amsterdam, The Netherlands. dicker@xs4all.nl
authors.forename: Gertjan
authors.initials: G
authors.lastname: Dicker
authors.forename: Peter
authors.initials: P
authors.lastname: Van Spronsen
authors.forename: Ronald
authors.initials: R
authors.lastname: Van Schijndel
authors.forename: Floris
authors.initials: F
authors.lastname: van Ginkel
authors.forename: Radu
authors.initials: R
authors.lastname: Manoliu
authors.forename: Heleen
authors.initials: H
authors.lastname: Boom
authors.forename: D Bram
authors.initials: DB
authors.lastname: Tuinzing
mesh_terms: D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002508:Cephalometry; D004812:Epidemiologic Methods; D005145:Face / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D019186:Mandibular Advancement; D008406:Masseter Muscle / Q000033:anatomy & histology* / Q000502:physiology; D008875:Middle Aged; D011626:Pterygoid Muscles / Q000033:anatomy & histology* / Q000502:physiology