Background and Aim: Detection of Horizontal root fracture is completely related to radiography and application of new methods is indispensable .The aim of this study was to compare the diagnostic accuracy of reverse contrast option of digital radiography with original images for detection of horizontal root fracture.

  Materials and Methods: In this diagnostic study, digital radiographs were taken from 40 maxillary anterior teeth mounted in a dry alveolar socket with vertical angles of 0° and 15 ⁰ .Root fractures were created in the horizontal plane on each root and after relocating root fragments radiographs were repeated in a same position. Images were processed with reverse contrast option and assessed by observers. Data were analyzed with proportion test and Cochran’s Q test.

  Results: There was no significant difference in sensitivity, specificity, PPV(Positive Predictive value) and NPV (Negative Predictive Value) between 0° and 15°radiographs in original and reverse contrast images. In either image groups, when fractures were certainly diagnosed by observers, 0°radiographs obtained higher sensitivities (P=0.014) Also when fractures were likely diagnosed , sensitivity and NPV were significantly higher for 0°radiographs (P=0.035) ,(P=0.023)respectively.

  Conclusion: The diagnostic accuracy of reverse contrast option of digital images are equal to original images, although 0° radiographs are more appropriate.

  Keywords : Digital radiography, Horizontal root fracture, Reverse contrast option