title: Reproducible X-ray projection geometry in edentulous patients.
abstract: OBJECTIVE
  To evaluate a novel fixation system for reproducible radiography in edentulous patients.
  
  
  METHODS
  A conventional extra-oral fixation system was modified with a filmholder and adjustable scales. For measuring reproducibility and angulation errors two rods and two balls were fixed on the alveolar crests of the maxilla and the mandible and angular variations were measured. One hundred radiographs of a conventional phantom were taken by one of the authors and by ten dental students. The angular disparity was calculated and intra- and interoperator precision determined.
  
  
  RESULTS
  The average time taken to assemble the fixation system was 4 min. The 95% confidence interval for precision of the single operator was less than 2.5 degrees in both the maxilla and mandible. The 95% confidence interval for precision of the ten students was less than 2.2 degrees for the maxilla and 2.7 degrees for the mandible. There was no significant difference (P>0.05) in interoperator precision.
  
  
  CONCLUSIONS
  The novel extra-oral fixation system appears to be a potential means of obtaining reproducible radiographs of edentulous patients.
authors.affiliation: Clinic for Cranio- and Maxillofacial Surgery, University of Münster, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Handschel
authors.forename: J
authors.initials: J
authors.lastname: Kleinheinz
authors.forename: M
authors.initials: M
authors.lastname: Kelker
authors.forename: I
authors.initials: I
authors.lastname: Reuter
authors.forename: U
authors.initials: U
authors.lastname: Joos
mesh_terms: D006801:Humans; D007575:Jaw, Edentulous / Q000000981:diagnostic imaging*; D008433:Mathematics; D011857:Radiographic Image Interpretation, Computer-Assisted; D011861:Radiography, Dental / Q000295:instrumentation*; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric