title: Evaluation of digital and geometric unsharpness in dental radiographs using an endodontic file model.
abstract: OBJECTIVE
  We sought to compare the effects of geometric and digital unsharpness.
  
  
  METHODS
  Endodontic files of sizes 6, 8, 10, and 15 were placed in the root canal of an extracted lower incisor in 3 different positions at 2-mm increments. Radiographs were taken with a GE 100 x-ray unit at magnification factors of 1.0, 1.1, 1.2, and 1.3. With the use of a flatbed scanner, each radiograph was digitized at resolutions of 75, 150, 300, and 600 dpi. Ten observers viewed the digital images and identified the positions of the end of the files and the end of the roots, as well as assessed image quality.
  
  
  RESULTS
  No significant differences were found between the resolutions of 300 and 600 dpi, nor between the magnifications of 1.0 and 1.1. Significant differences were found between the magnification of 1.3 and the others and the resolution of 75 dpi and the others for all of the files.
  
  
  CONCLUSIONS
  Geometric unsharpness has little relevance in clinical dental radiography. Increasing scanning resolution to 600 dpi did not improve accuracy with respect to recognizing the position of endodontic files.
authors.affiliation: Section of Oral and Maxillofacial Radiology, School of Dentistry, Division of Diagnostic and Surgical Services, University of California, Los Angeles 90095-1658, USA. elhamr@dent.ucla.edu
authors.forename: Elham
authors.initials: E
authors.lastname: Radan
authors.forename: Colin
authors.initials: C
authors.lastname: Price
mesh_terms: D000704:Analysis of Variance; D003762:Dental Instruments; D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging*; D006801:Humans; D007180:Incisor / Q000000981:diagnostic imaging; D015588:Observer Variation; D011858:Radiographic Magnification; D019252:Radiography, Dental, Digital; D015203:Reproducibility of Results; D018915:Root Canal Preparation / Q000295:instrumentation; D018709:Statistics, Nonparametric