title: A comparison of three-dimensional stress distribution and displacement of naso-maxillary complex on application of forces using quad-helix and nickel titanium palatal expander 2 (NPE2): a FEM study.
abstract: BACKGROUND
  Our objectives are to analyse and to compare the stress distribution and displacement of the craniofacial structures, following the application of forces from quad-helix and Nickel Titanium Palatal Expander-2 (NPE2) using finite element analysis.
  
  
  METHODS
  Three-dimensional finite element models of young dried human skull, quad-helix appliance and NPE2 were constructed, and the initial activation of the expanders was stimulated to carry out the analysis and to evaluate the Von Misses stresses and displacement.
  
  
  RESULTS
  Both the models demonstrated the highest stresses at the mid-palatal suture, with maximum posterior dislocation. The second highest stress was recorded at the fronto-zygomatic suture. The pattern of stress distribution was almost similar in both the groups, but NPE2 revealed lower magnitude stresses than quad-helix. The only exception being quad-helix model showed high stress levels around pterygo-maxillary suture whereas minimal stress around pterygo-maxillary suture was noticed after NPE2 activation. The cusp of the erupting canine and the erupting mesiobuccal cusp of the second molar showed outward, backward and downward displacement signifying increase in their eruption pattern following maxillary expansion.
  
  
  CONCLUSIONS
  Maxillary expansion using quad-helix and NPE2 can be used in posterior crossbite correction in cases where maximum skeletal changes are desirable at a younger age; it is furthermore effective in treating young patients with impacted or displaced teeth. Quad-helix and NPE2 produced acceptable forces for orthopaedic treatment even after being orthodontic appliances; their clinical application should be correctly planned as the effects of these appliances are largely age dependent.
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Al-Badar Dental College and Hospital, Gulbarga, Karnataka, India. dr.avinashsajjan@gmail.com.
authors.forename: Avinash
authors.initials: A
authors.lastname: Kumar
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Al-Badar Dental College and Hospital, Gulbarga, Karnataka, India.
authors.forename: Hajra
authors.initials: H
authors.lastname: Ghafoor
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Al-Badar Dental College and Hospital, Gulbarga, Karnataka, India.
authors.forename: Arifa
authors.initials: A
authors.lastname: Khanam
mesh_terms: D000497:Alloys / Q000737:chemistry*; D002648:Child; D003198:Computer Simulation; D017076:Computer-Aided Design; D003393:Cranial Sutures / Q000502:physiology; D003481:Cuspid; D003724:Dental Arch / Q000502:physiology; D003799:Dental Stress Analysis; D020342:Finite Element Analysis; D006801:Humans; D008310:Malocclusion / Q000628:therapy; D008437:Maxilla / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D008953:Models, Anatomic; D008954:Models, Biological; D008963:Molar; D009295:Nasal Bone / Q000502:physiology; D009666:Nose / Q000033:anatomy & histology / Q000502:physiology*; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation* / Q000379:methods; D016382:Orthodontic Appliance Design; D009967:Orthodontic Appliances; D010155:Palatal Expansion Technique / Q000295:instrumentation*; D010159:Palate / Q000737:chemistry*; D021362:Palate, Hard / Q000502:physiology; D012886:Skull / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed; D015050:Zygoma / Q000502:physiology
chemical_list: D000497:Alloys; C013616:nitinol