title: Three-dimensional finite element analysis of stress distribution and displacement of the maxilla following surgically assisted rapid maxillary expansion.
abstract: OBJECTIVE
  The aim of this study was to investigate the displacement and stress distributions during surgically assisted rapid maxillary expansion under different surgical conditions.
  
  
  METHODS
  3-dimensional finite element model of a maxilla with a Hyrax appliance was constructed and an expansion force of 6000 grams was applied using the expansion screw. According to the surgical procedures, 5 groups including a control group without surgery (Group I) were simulated. The experimental groups were as follows; Group II (Le Fort I osteotomy), Group III (Le Fort I osteotomy and paramedian osteotomy), Group IV (Le Fort I osteotomy and pterygomaxillary separation), and Group V (Le Fort I osteotomy, paramedian osteotomy, and pterygomaxillary separation).
  
  
  RESULTS
  Displacement of the maxilla gradually increased from Group 1 to Group 5 in all three planes of space, indicating that combination of the Le Fort I osteotomy with paramedian osteotomy and pterygomaxillary separation produce greatest displacement of the maxilla. By surgical relief, the stress exerted on anchor teeth was significantly reduced.
  
  
  CONCLUSIONS
  The results suggested that the combination of Le Fort I and paramedian osteotomy with pterygomaxillary separation is an effective procedure for increasing the expansion of the maxilla with lower side effects caused by excessive stresses around the anchor teeth.
authors.affiliation: Department of Craniomaxillofacial surgery, Kangnam St Mary's Hospital, Medical College, the Catholic University of Korea, Seocho-gu, Seoul, Republic of Korea.
authors.forename: Un Ae
authors.initials: UA
authors.lastname: Han
authors.forename: Yoonji
authors.initials: Y
authors.lastname: Kim
authors.forename: Je Uk
authors.initials: JU
authors.lastname: Park
mesh_terms: D003198:Computer Simulation; D003799:Dental Stress Analysis / Q000379:methods*; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional; D008437:Maxilla / Q000033:anatomy & histology* / Q000601:surgery; D008953:Models, Anatomic; D010027:Osteotomy / Q000706:statistics & numerical data*; D010155:Palatal Expansion Technique / Q000706:statistics & numerical data*