Several studies have shown that, there are some advantages of Digital Radiography compared with conventional radiography. Many studies have been performed with the aim of improving radiographic interpretation through modern computerized technology. It has been shown that diagnostic accuracy improved when overlaying structure can be removed by subtraction technique and then this technology evaluate ability to detect periodontal lesion. In this experimental study that was done in radiology department of Isfahan, dental school, 5 block of dried mandible established in abutments. A digital sensor and X-ray tube were established on the another abutment too. Radiographs were made from 26 alveolar crestal regions as primary Radiographs using Kvp = 70 and t = 0.01s. With a round bur artificial periodontal lesions, were simulated on 16 crestal regions out of 26, then second radiagraphs were made from all 26 crestal regions, whitout any changes in position of X-ray and tube. Two radiographs were subtracted by a soft ware. Radiography and subtraction radiography were compared by 2 post graduate students of periodontic. Results analyzed with statistical methods and SPSS soft ware. The willcoxon test was applied for assessment of statistically significant differences with respect of sensitivity, specificity and positive diagnostic value in diagnosis of crestal changes in digital image and subtracted digital images. Accuracy of digital subtraction radiography (DSR): sensitivity and specificity was better than conventional digital radiography. The digital subtraction method may be useful in the quantification of Alveolar bone loss in clinic, more studies about advantages and disadvantages of DSR is recommended.