title: A computed tomographic image study on the thickness of the infrazygomatic crest of the maxilla and its clinical implications for miniscrew insertion.
abstract: BACKGROUND
  The purpose of this study was to measure the thickness of the infrazygomatic (IZ) crest above the maxillary first molar at different angles and positions to the maxillary occlusal plane. These measurements were then used to derive clinical implications and guidance for inserting miniscrews in the IZ crest without injuring the mesiobuccal root of the maxillary first molar.
  
  
  METHODS
  Computed tomographic images of 16 adults were used. For each subject, on the coronal slice of the computed tomographic image containing the IZ crest and mesiobuccal root of the maxillary first molar, the IZ crest thickness and the miniscrew insertion position were measured by postulating that the miniscrew would be inserted at each 5 degrees increment from 40 degrees to 75 degrees to the maxillary occlusal plane.
  
  
  RESULTS
  The IZ crest thickness above the maxillary first molar ranged from 5.2 +/- 1.1 mm to 8.8 +/- 2.3 mm, measured at 40 degrees to 75 degrees to the maxillary occlusal plane and 13 to 17 mm above the maxillary occlusal plane.
  
  
  CONCLUSIONS
  By adopting 6 mm as the minimal IZ crest thickness for sustaining a miniscrew well throughout treatment and avoiding injury to the mesiobuccal root of the maxillary first molar, the clinical implication for miniscrew placement in the IZ crest of an adult is to insert it 14 to 16 mm above the maxillary occlusal plane and the maxillary first molar at an angle of 55 degrees to 70 degrees to the maxillary occlusal plane.
authors.affiliation: Department of Orthodontics and Craniofacial Dentistry, Chang Gung Memorial Hospital, Taipei, Taiwan. lioueric@ms19.hinet.net
authors.forename: Eric J W
authors.initials: EJ
authors.lastname: Liou
authors.forename: Po-Hsun
authors.initials: PH
authors.lastname: Chen
authors.forename: Yu-Chih
authors.initials: YC
authors.lastname: Wang
authors.forename: James Chen-Yi
authors.initials: JC
authors.lastname: Lin
mesh_terms: D000328:Adult; D001863:Bone Screws; D002508:Cephalometry; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008963:Molar / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D014092:Tooth Root / Q000000981:diagnostic imaging; D015050:Zygoma / Q000033:anatomy & histology* / Q000000981:diagnostic imaging