title: Biomechanical effects of maxillary expansion on a patient with cleft palate: A finite element analysis.
abstract: BACKGROUND
  The aims of this study were to evaluate the effects of rapid palatal expansion on the craniofacial skeleton of a patient with unilateral cleft lip and palate (UCLP) and to predict the points of force application for optimal expansion using a 3-dimensional finite element model.
  
  
  METHODS
  A 3-dimensional finite element model of the craniofacial complex with UCLP was generated from spiral computed tomographic scans with imaging software (Mimics, version 13.1; Materialise, Leuven, Belgium). This model was imported into the finite element solver (version 12.0; ANSYS, Canonsburg, Pa) to evaluate transverse expansion forces from rapid palatal expansion. Finite element analysis was performed with transverse expansion to achieve 5 mm of anterolateral expansion of the collapsed minor segment to simulate correction of the anterior crossbite in a patient with UCLP.
  
  
  RESULTS
  High-stress concentrations were observed at the body of the sphenoid, medial to the orbit, and at the inferior area of the zygomatic process of the maxilla. The craniofacial stress distribution was asymmetric, with higher stress levels on the cleft side. When forces were applied more anteriorly on the collapsed minor segment and more posteriorly on the major segment, there was greater expansion of the anterior region of the minor segment with minimal expansion of the major segment.
  
  
  CONCLUSIONS
  The transverse expansion forces from rapid palatal expansion are distributed to the 3 maxillary buttresses. Finite element analysis is an appropriate tool to study and predict the points of force application for better controlled expansion in patients with UCLP.
authors.affiliation: Assistant professor, Department of Orthodontics, School of Dentistry, University of California at Los Angeles, Los Angeles, Calif.
authors.forename: Haofu
authors.initials: H
authors.lastname: Lee
authors.affiliation: Dental student, Department of Orthodontics, School of Dentistry, University of California at Los Angeles, Los Angeles, Calif.
authors.forename: Alan
authors.initials: A
authors.lastname: Nguyen
authors.affiliation: Assistant professor, Department of Orthodontics, School of Dentistry, University of California at Los Angeles, Los Angeles, Calif.
authors.forename: Christine
authors.initials: C
authors.lastname: Hong
authors.affiliation: Orthodontic resident, Department of Orthodontics, School of Dentistry, University of California at Los Angeles, Los Angeles, Calif.
authors.forename: Paul
authors.initials: P
authors.lastname: Hoang
authors.affiliation: Dental student, Department of Orthodontics, School of Dentistry, University of California at Los Angeles, Los Angeles, Calif.
authors.forename: John
authors.initials: J
authors.lastname: Pham
authors.affiliation: Professor and chair, Department of Orthodontics, School of Dentistry, University of California at Los Angeles, Los Angeles, Calif. Electronic address: haofulee@ucla.edu.
authors.forename: Kang
authors.initials: K
authors.lastname: Ting
mesh_terms: D000652:Amniotic Band Syndrome / Q000150:complications; D001696:Biomechanical Phenomena; D002648:Child; D002972:Cleft Palate / Q000503:physiopathology / Q000628:therapy*; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional; D010155:Palatal Expansion Technique; D036542:Tomography, Spiral Computed