title: Effect of head positioning in panoramic radiography on vertical measurements: an in vitro study.
abstract: OBJECTIVE
  To assess whether it is possible to make accurate vertical measurements of the jaws from panoramic radiographs.
  
  
  METHODS
  Five dry skulls were shifted 5 mm forwards and backwards and tilted 5 degrees up and down in the sagittal plane. Panoramic radiographs of each skull were obtained in nine different positions. In the maxilla, three reference lines were used and vertical measurements were made at the distal surfaces of the first premolar and first molar and in the midline. In the mandible, measurements were made at the distal surfaces of the first premolar and first molar, and at the mental foramen on both sides, and in the midline. The points and lines were marked manually and the radiographs were digitized, magnified and measured.
  
  
  RESULTS
  Sagittal shifting and tilting had only a slight effect on measurements in the mandible. Sagittal tilting of the head had the greatest effect on all the measurements made from the line between the articular eminences to the alveolar crest, as well as measurements in the maxillary midline.
  
  
  CONCLUSIONS
  The line between the articular eminences is unsuitable as a reference line for measurements of the tooth-bearing areas. A slight misalignment of the head does not significantly affect the vertical measurements in the mandible or of the posterior maxilla if the reference lines are in the same vertical plane as the teeth.
authors.affiliation: Department of Prosthetic Dentistry, University of Helsinki, Finland.
authors.forename: Q
authors.initials: Q
authors.lastname: Xie
authors.forename: K
authors.initials: K
authors.lastname: Soikkonen
authors.forename: J
authors.initials: J
authors.lastname: Wolf
authors.forename: K
authors.initials: K
authors.lastname: Mattila
authors.forename: M
authors.initials: M
authors.lastname: Gong
authors.forename: A
authors.initials: A
authors.lastname: Ainamo
mesh_terms: D000704:Analysis of Variance; D002508:Cephalometry / Q000379:methods*; D003758:Dental Implantation, Endosseous; D006801:Humans; D007568:Jaw / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D016014:Linear Models; D011862:Radiography, Panoramic / Q000379:methods*; D012016:Reference Values; D015203:Reproducibility of Results; D014716:Vertical Dimension