title: Comparison of the skeletal and dental changes of tooth-borne vs. bone-borne expansion devices in surgically assisted rapid palatal expansion: A finite element study.
abstract: BACKGROUND
  The aim of this study was to compare the skeletal and dental changes of a tooth-borne (Hyrax) and a bone-borne (Smile distractor) expansion devices using three-dimensional model of a human skull.
  
  
  METHODS
  A finite element model of human skull was generated using data from 3-D CT scans of an 11-year-old female child. Then a Hyrax expander (tooth-borne appliance) and Smile distractor (bone-borne appliance) in three different positions were adapted to the finite element model and expanded for 0.5 mm simulating the clinical situation. The 3-D pattern of displacement and stress distribution was then analyzed.
  
  
  RESULTS
  The results of this study showed that screw position affects the stress and displacement pattern within the nasomaxillary complex and maxillary dental arch.
  
  
  CONCLUSIONS
  Closer teeth feel more stress and undergo more displacement than the farther ones. Moreover, skeletal effects of the Smile distractor were greater than of Hyrax in all different positions.
authors.affiliation: Dental Research Center, Research Institute of Dental Sciences, Shahid Beheshti University of Medical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Azita
authors.initials: A
authors.lastname: Tehranchi
authors.affiliation: Orthodontic Department, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Nazila
authors.initials: N
authors.lastname: Ameli
authors.affiliation: Orthodontic Department, Shahed Dental School, Tehran, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Najirad
authors.affiliation: PhD student, Mechanics of Agricultural Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.
authors.forename: Fatemeh Sadat
authors.initials: FS
authors.lastname: Mirhashemi
keywords: Dental; expansion device; finite element method; skeletal