Comparation of accuracy of digital periapical radiography and Cone Beam Computed Tomography subtraction images in the diagnosis of simulated recurrent carries in three direct tooth colored restorative materials

Abstract

Introduction: Early detection of recurrent caries is also currently one of the most challenging topics in dentistry. Since these lesions often do not have clear clinical signs in the early stages, more radiographs are used. Considering the importance of imaging frequency in radiographic systems for periodic diagnosis of recurrent carious lesions, The purpose of this study was comparision of digital periapical and Cone Beam Computed Tomography subtraction radiography in the diagnosis of simulated recurrent caries in three direct tooth colored restorative materials.

Methods and Materials: In this experimental study, 24 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 CBCT 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 CBCT and periapical radiography were taken. Finally, subtraction was performed on the obtained images (CBCT 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: necessary width of the caries like lesion to detect in periapical digital subtraction radiography, regardless of the restorative material, was 7 times of the thickness of the bur head diameter, while this value was 8 times in CBCT 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 6/5 and 8 times of the thickness of the bur head diameter, respectively. Based on the results of Kruskal-Wallis test, the effect of imaging technique on the frequency of imaging was statistically significant (P < 0.001). Also, the effect of type (radiopacity) of restorative material on the frequency of imaging was statistically significant among the studied groups (P < 0.001).

Conclusion: According to this study, The accuracy of digital periapical subtraction radiography in diagnosing recurrent caries is higher than CBCT subtraction radiography. Also, recurrent caries lesions under restorative material with a higher radiopacity (Tetric N-Ceram resin composite) are detected earlier.