title: Displaced premolars in panoramic radiography: fact or fallacy?
abstract: OBJECTIVE
  To test the null hypothesis that there is no difference between premolar position visualized on panoramic radiographs (PRs) and lateral headfilms (LHs).
  
  
  METHODS
  The prevalence of differences in the direction of crown angulation between PR and LH was assessed. Furthermore, brass wire markers with different sagittal and transverse angulations were placed in a dry skull. With the markers in place, LHs and PRs were taken.
  
  
  RESULTS
  A difference in the direction of crown angulation of unerupted second premolars between PR and LH occurred in 19.5% of patients. The reason for the angulation differences is a buccolingual orientation of the tooth, which appears as a mesiodistal angulation on the PR.
  
  
  CONCLUSIONS
  The null hypothesis was rejected since in one-fifth of the patients premolar projection differs between the panoramic radiograph and the lateral headfilm.
authors.affiliation: Department of Orthodontics, University of Berne, Berne, Switzerland.
authors.forename: Nasila
authors.initials: N
authors.lastname: Nohadani
authors.forename: Yango
authors.initials: Y
authors.lastname: Pohl
authors.forename: Sabine
authors.initials: S
authors.lastname: Ruf
mesh_terms: D016477:Artifacts; D001641:Bicuspid / Q000000981:diagnostic imaging*; D002648:Child; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008297:Male; D011862:Radiography, Panoramic; D011795:Surveys and Questionnaires; D019228:Tooth Crown / Q000000981:diagnostic imaging; D014097:Tooth, Unerupted / Q000000981:diagnostic imaging*