title: Reliability of the vertical magnification factor on panoramic radiographs: clinical implications for posterior mandibular implants.
abstract: OBJECTIVE
  Panoramic radiographs allow evaluation of the available bone height for implant treatment planning while imparting a low radiation dose. As panoramic radiography produces image distortion, reference objects are required to determine the exact magnification. This study aims to estimate a panoramic unit's vertical magnification factor (MF) by measuring the length of dental implants used as radiopaque reference objects on postoperative panoramic radiographs. We compared our findings to the vertical MF listed by the panoramic unit manufacturer, and studied the reproducibility and accuracy of our measuring method by analyzing the inter- and intraobserver agreements.
  
  
  METHODS
  Using a digital calliper, we measured the length of 32 implants on 17 postoperative panoramic radiographs taken with a Scanora unit. The implants were 10mm-long standard Straumann implants placed in the posterior segments of mandibles. The MF was calculated by dividing the implant's radiological length by the implant's real length.
  
  
  RESULTS
  The mean calculated vertical MF was 1.27 ± 0.01 (1.245-1.295) and was lower than the manufacturer's MF (1.3). The vertical MF was 1.28 ± 0.01 in the premolar and 1.27 ± 0.01 in the molar regions. There was an excellent intraobserver reliability (0.96 for observer 1; 0.93 for observer 2) and a good interobserver reliability (0.85 at measurement session 1; 0.8 at measurement session 2)
  
  
  CONCLUSIONS
  The observed reliability of the MF confirms that a panoramic radiograph can be used for preoperative implant length evaluation in the posterior mandibular segments. MF stability should be verified with other panoramic units. In clinical practice, using the implant length as a reference object on postoperative panoramic radiographs is a simple and effective evaluation method to estimate a panoramic unit's MF.
authors: Department of Oral Surgery, Oral Medicine, Oral and Maxillofacial Radiology, School of Dental Medicine, University of Geneva, Geneva, Switzerland. lydia.vazquez@unige.ch
authors: Lydia
authors: L
authors: Vazquez
authors: Yassin
authors: Y
authors: Nizam Al Din
authors: Urs
authors: U
authors: Christoph Belser
authors: Christophe
authors: C
authors: Combescure
authors: Jean-Pierre
authors: JP
authors: Bernard
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003757:Dental Implantation; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging* / Q000601:surgery*; D008875:Middle Aged; D010347:Patient Care Planning; D011858:Radiographic Magnification / Q000379:methods*; D011862:Radiography, Panoramic; D015203:Reproducibility of Results