The effects of noise reduction, sharpening, enhancement, and image magnification on diagnostic accuracy of a photostimulable phosphor system in the detection of non-cavitated approximal dental caries

Purpose: Contrast, sharpness, enhancement, and density can be changed in digital systems. The important question is to what extent the changes in these variables affect the accuracy of caries detection. Materials and Methods: Forty eight extracted human posterior teeth with healthy or proximal caries surfaces were imaged using a photostimulable phosphor (PSP) sensor. All original images were processed using a six-step method: (1) applying Sharpening 2 and Noise Reduction processing options to the original images; (2) applying the Magnification 1: 3 option to the image obtained in the first step; (3) enhancing the original images by using the Diagonal/ option; (4) reviewing the changes brought about by the third step of image processing and then, applying Magnification 1: 3; (5) applying Sharpening UM to the original images; and (6) analyzing the changes brought about by the fifth step of image processing, and finally, applying Magnification 1: 3. Three observers evaluated the images. The tooth sections were evaluated histologically as the gold standard. The diagnostic accuracy of the observers was compared using a chi-squared test. Results: The accuracy levels irrespective of the image processing method ranged from weak (18.8%) to intermediate (54.2%), but the highest accuracy was achieved at the sixth image processing step. The overall diagnostic accuracy level showed a statistically significant difference (p=0.0001). Conclusion: This study shows that the application of Sharpening UM along with the Magnification 1: 3 processing option improved the diagnostic accuracy and the observer agreement more effectively than the other processing procedures.