Materials and Methods : This experimental observational study evaluated 39 extracted teeth. All roots, except for the palatal root of upper molars,were hypotheticallydividedinto apical and coronal sections.Half these sites were considered as the control group .Buccal cavities were randomly made in the remaining sectionsusing # 1/2,2 and 4 round burrs.Each tooth was imaged using a CCD-based digital system and E-speed film. Radiographs were taken at 0 and 20˚ mesial angulation .Six image groups were interpreted by two experienced oral and maxillofacial radiologists and one endodontist.Conventional and enhanced digital radiographs were also takenat 0 and 20˚ mesial angulation. Conventional radiographs were viewedat 2X magnification by a magnifying glass. Sensitivity, specificity,false positive and false negative percentages and accuracyof each method were compared with the gold standard. The degree of agreement among these techniques was measuredbykappa coefficient .

  Results: Conventional radiography at 2X magnification had the highest sensitivity and specificity. No significant difference was found in sensitivity of digital radiography and enhanced digital radiography. Enhanced digital radiography ranked second in terms of specificity. Conventional radiography at 2X magnification followed by enhanced digital radiography had the highest diagnostic accuracy. Mesial angulation of the cone increasedsensitivity and decreased specificity in all three techniques and thus, it only improved the diagnostic accuracy of digital radiography with no significant effect on the other two techniques.The degree of agreement between the two digital techniques was higher (k=0.68) .

  Conclusion: Diagnostic efficacy of conventional radiography at 2X magnification is more than digital radiographs for detection of external root resorption .