title: Stress and displacement between maxillary protraction with miniplates placed at the infrazygomatic crest and the lateral nasal wall: a 3-dimensional finite element analysis.
abstract: BACKGROUND
  The purpose of this study was to compare the pattern and amount of stress and displacement between maxillary protraction with miniplates placed at the infrazygomatic crest and the lateral nasal wall.
  
  
  METHODS
  Three-dimensional finite element models for the skull and the curvilinear type of miniplate were constructed. After a protraction force (500 g/side) was applied to the distal end of the miniplate with a forward and 30° downward vector to the maxillary occlusal plane, stress distributions in the circummaxillary sutures and displacements of the surface landmarks were analyzed.
  
  
  RESULTS
  There was a difference in the maximum stress distribution area according to the site of the miniplate: infrazygomatic crest and middle part of the maxilla in the infrazygomatic crest and paranasal area adjacent to the pyriform aperture in the lateral nasal wall. Stress values of the frontonasal, frontomaxillary, zygomaticomaxillary, and pterygomaxillary sutures were greater in the infrazygomatic crest than in the lateral nasal wall. The site of the miniplate produced differences in the major displacement areas: infrazygomatic crest, maxillary dentition, anterior maxilla, and upper part of the maxillary tuberosity in the infrazygomatic crest and the lateral nasal wall, maxillary dentition, anterior maxilla, and lower part of the maxillary tuberosity in the lateral nasal wall. The lateral nasal wall exhibited forward, downward, and outward displacements of ANS, Point A, and prosthion. However, the infrazygomatic crest showed forward and upward displacements of ANS, Point A, and prosthion, and outward displacement of the zygomatic process of the maxilla and the maxillary process of the zygomatic bone.
  
  
  CONCLUSIONS
  The site of miniplate placement should be considered to obtain proper stress and displacement values in different areas with maxillary hypoplasia.
authors.affiliation: Assistant professor, Department of Orthodontics, Section of Dentistry, Seoul National University, Bundang Hospital, Seongnam, Gyeonggi Province, Republic of Korea.
authors.forename: Nam-Ki
authors.initials: NK
authors.lastname: Lee
authors.affiliation: Professor, Department of Orthodontics, School of Dentistry, Dental Research Institute, Seoul National University, Seoul, Republic of Korea. Electronic address: drwhite@unitel.co.kr.
authors.forename: Seung-Hak
authors.initials: SH
authors.lastname: Baek
mesh_terms: D000293:Adolescent; D059925:Anatomic Landmarks / Q000473:pathology; D001641:Bicuspid / Q000473:pathology; D001696:Biomechanical Phenomena; D001860:Bone Plates; D017076:Computer-Aided Design; D003393:Cranial Sutures / Q000473:pathology; D003481:Cuspid / Q000473:pathology; D005115:Extraoral Traction Appliances; D005260:Female; D020342:Finite Element Analysis; D005624:Frontal Bone / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008437:Maxilla / Q000473:pathology / Q000601:surgery*; D009295:Nasal Bone / Q000473:pathology; D009296:Nasal Cavity / Q000601:surgery*; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation; D010155:Palatal Expansion Technique / Q000295:instrumentation; D012658:Sella Turcica / Q000473:pathology; D013100:Sphenoid Bone / Q000473:pathology; D013314:Stress, Mechanical; D013701:Temporal Bone / Q000473:pathology; D014057:Tomography, X-Ray Computed / Q000379:methods; D014092:Tooth Root / Q000473:pathology; D015050:Zygoma / Q000601:surgery*