title: 3D CT based rating of unilateral impacted canines.
abstract: OBJECTIVE
  The aim of this study was to develop a reference system for multislice computed tomography (MSCT) images to determine of the location of impacted teeth in metric terms.
  
  
  METHODS
  The CT data of 17 patients with unilateral impacted maxillary canines were selected retrospectively from existing MSCT data sets. In a reference coordinate system, defined by anterior nasal spine (ANS), posterior nasal spine (PNS), and A-point, the axis length and the inclination of the canines were determined and impacted and non-impacted canines were compared.
  
  
  RESULTS
  There were significant differences between the impacted and non-impacted canines (p ≤ 0.0003) for all inclinations and the lengths in the x- and z-axes. The measurement of the inclination and sections of the impacted and non-impacted canine tooth axes showed sufficient repeatability and reproducibility.
  
  
  CONCLUSIONS
  The coordinate system proved to be suitable for the exact metric localization of impacted teeth.
authors.affiliation: Department of Orthodontics and Orofacial Orthopedics, Universitätsklinikum Erlangen, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hanke
authors.forename: Ursula
authors.initials: U
authors.lastname: Hirschfelder
authors.forename: Thomas
authors.initials: T
authors.lastname: Keller
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Hofmann
mesh_terms: D000293:Adolescent; D002508:Cephalometry / Q000379:methods; D002648:Child; D003481:Cuspid / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008437:Maxilla / Q000000981:diagnostic imaging*; D061330:Multidetector Computed Tomography / Q000379:methods*; D009295:Nasal Bone / Q000000981:diagnostic imaging; D009296:Nasal Cavity / Q000000981:diagnostic imaging; D015588:Observer Variation; D009811:Odontometry / Q000379:methods; D015203:Reproducibility of Results; D012189:Retrospective Studies; D019227:Tooth Apex / Q000000981:diagnostic imaging; D019228:Tooth Crown / Q000000981:diagnostic imaging; D014095:Tooth, Impacted / Q000000981:diagnostic imaging*