title: Localization of ectopic maxillary canines -- is CBCT more accurate than conventional horizontal or vertical parallax?
abstract: OBJECTIVE
  To compare the accuracy of cone-beam CT (CBCT) with conventional horizontal and vertical parallax for the localization of ectopic maxillary canines.
  
  
  METHODS
  Observational study.
  
  
  METHODS
  A typodont was constructed using human teeth embedded in radio-dense impression material, containing a simulated ectopic canine. Image sets (vertical/horizontal parallax and CBCT scans) were obtained for nine positions. A photograph confirmed the true position of the canine. Six observers used horizontal (HP) and vertical (VP) parallax techniques with conventional radiographs and the axial, coronal and sagittal CBCT views to locate the canine tip. Images were manipulated as required using proprietary software (http://www.carestream.com and http://www.i-cat.com). Intra-observer reproducibility was calculated by one observer re-evaluating the image sets after 2 months. Individual observer validity was calculated in relation to the photographic position of the canine using weighted Kappa. Differences in the proportion of correct locations between CBCT and vertical/horizontal parallax were tested using McNemar tests (P<0·05).
  
  
  RESULTS
  Intra- and inter-observer agreements were excellent (0·8985) and substantial (0·7528), respectively. Individual observer validity was substantial-excellent (0·7368-0·900). The canine position was correctly identified in 94% of cases located using CBCT, 83% using HP and 65% using VP. The differences between CBCT and vertical and horizontal parallax were highly statistically significant (P<0·01).
  
  
  CONCLUSIONS
  CBCT is more accurate than either horizontal or vertical parallax for the localization of ectopic maxillary canine teeth.
authors.affiliation: G. McIntyre, Department of Orthodontics, NHS Tayside, 2 Park Place, Dundee DD1 4HR, UK grant.mcintyre@nhs.net.
authors.forename: Paul S
authors.initials: PS
authors.lastname: Serrant
authors.forename: Grant T
authors.initials: GT
authors.lastname: McIntyre
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Thomson
mesh_terms: D054893:Cone-Beam Computed Tomography / Q000379:methods* / Q000706:statistics & numerical data; D003481:Cuspid / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008437:Maxilla / Q000000981:diagnostic imaging*; D015588:Observer Variation; D019047:Phantoms, Imaging; D010781:Photography / Q000379:methods; D011858:Radiographic Magnification; D016300:Radiography, Bitewing / Q000379:methods* / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D014079:Tooth Eruption, Ectopic / Q000000981:diagnostic imaging*
keywords: CBCT; horizontal parallax; impacted canine; vertical parallax