title: The reliability of using postero-anterior cephalometry and cone-beam CT to determine transverse dimensions in clinical practice.
abstract: OBJECTIVE
  This study primarily aimed to assess the accuracy of classically-advocated reference points for the measurement of transverse jaw-base and dental relationships using conventional Postero-Anterior Cephalometry (PAC) and Cone-Beam Computed Tomography (CBCT).
  
  
  METHODS
  PAC and CBCT images were collected from 31 randomly selected orthodontic patients (12 males, 19 females), all of whom had a full permanent dentition. The transverse widths of the maxilla, mandible and the dentition were measured using reference points on both image modalities. Confidence intervals, intra-class coefficients and Bland Altman plots were used to assess the measurement differences derived from the two acquirement methods.
  
  
  RESULTS
  Measurements on PAC and CBCT images demonstrated statistically significant differences in the majority of the assessed variables. The interjugal (J-J) width was one of only two variables which did not demonstrate a statistically significant difference on image comparison. The mean differences of the antegonial width (Ag-Ag) (-4.44mm, 95% CI -5.38 to -3.51) represented the greatest difference between the imaging techniques. The application of these points to a transverse skeletal analysis (J-J/Ag-Ag ratio) revealed that five of the 31 subjects (16%) recorded 'false positive' readings according to the derived data.
  
  
  CONCLUSIONS
  It is recommended that clinicians are cautious when interpreting and making decisions related to transverse dimensions derived from a PAC. The PAC has a higher tendency to falsely identify individuals who require maxillary expansion procedures based on conventional clinical criteria. The errors primarily associated with identifying structures which represent the width of the mandible are significant in both PAC and CBCT techniques and require further investigation. It is postulated that the confounding effects of overlying soft tissues have a sianificant impact on a clinician's ability to identify relevant landmarks.
authors.affiliation: Department of Orthodontics, The University of Western Australia, Crawley, Western Australia, Australia.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Tai
authors.forename: Mithran Suresh
authors.initials: MS
authors.lastname: Goonewardene
authors.forename: Kevin
authors.initials: K
authors.lastname: Murray
authors.forename: Bernard
authors.initials: B
authors.lastname: Koong
authors.forename: Syed Mohammed Shamsul
authors.initials: SM
authors.lastname: Islam
mesh_terms: D000293:Adolescent; D000539:Alveolar Process / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D059925:Anatomic Landmarks / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D002508:Cephalometry / Q000706:statistics & numerical data*; D002648:Child; D054893:Cone-Beam Computed Tomography / Q000706:statistics & numerical data*; D003481:Cuspid / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D003724:Dental Arch / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D005147:Facial Bones / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000706:statistics & numerical data; D008297:Male; D008334:Mandible / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008437:Maxilla / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D008963:Molar / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D015203:Reproducibility of Results; D014070:Tooth / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D019228:Tooth Crown / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D015050:Zygoma / Q000033:anatomy & histology / Q000000981:diagnostic imaging