Comparision of Accuracy of Digital Periapical and Panoramic Subtraction Radiography in the Diagnosis of Simulated Recurrent Caries inThree Direct Tooth Colored Restorative Materials

Abstract

Aim: The purpose of this study was comparision of digital periapical and panoramic subtraction radiography in the diagnosis of simulated recurrent caries in three direct tooth colored restorative materials.

Materials and Methods: In this experimental study, six healthy human molar teeth without previous restoration and caries extracted due to periodontal problems were prepared. The teeth were embedded in acryl and acrylic base was made to place them. Class II mesial and distal simple box cavities were prepared in each tooth with the same dimensions. The teeth were divided into three groups according to the type of restorative material used as follows: 1- Tetric N Ceram composite resin, 2- Z350 composite resin and 3- Resin Modified Glass Ionomer. Baseline digital panoramic and periapical radiography were taken. Then, to simulate marginal recurrent caries, a thin wedge shape layer of tooth at the gingival margin of restoration was removed by using a needle diamond bur equal with one tenth of the bur head length. At each stage, the width of the cavity in the bacolingual direction equal with the thickness of the bur head diameter increased, similar to the previous step. Then, digital panoramic and periapical radiography were taken. Finally, subtraction was performed on the obtained images (panoramic and periapical). The resulting subtracted images were evaluated by two observers to detect caries. The effect of two variables of restorative materials and radiography technique were reported using descriptive statistical methods (mean, standard deviation). In order to evaluate the effect of imaging method and type of restorative material on the number of radiographys, kruksal wallis and Mann-Whitney U test were used. The significant level (P <0.05) was considered. Results: The necessary width of the caries like lesion to detect in periapical digital subtraction radiography, regardless of the restorative material, was 6.5 times of the thickness of the bur head diameter, while this value was 10 times in panoramic digital subtraction radiography. The lowest and highest width of the caries like lesion required for detection, regardless of imaging method, were observed in Tetric N-Ceram composite resin and Resin Modified Glass Ionomer, respectively, which were 7.5 and 8.5 times of the thickness of the bur head diameter, respectively. Based on the results of Kruskal-Wallis test, the effect of restorative material on the frequency of imaging was not statistically significant among the studied groups (P = 0.28), but the effect of imaging technique on the frequency of imaging was statistically significant (P < 0.001).

Conclusion: According to this study, Recurrent caries lesions are detected much earlier by digital periapical subtraction radiography than digital panoramic digital subtraction radiography. The radiopacity of the restorative material has a lesser effect on the early detection of this type of lesion.