In Vitro Evaluation of The Effect of Thermal Cycle on Microleakage in Different Adhesive Systems

Background Microleakage is defined as the passage of bacteria, oral fluids, molecules, and ions through the microgap between restorative materials and the cavity wall. Microleakage is a significant factor affecting the longevity of restorations and contributing to the need for replacement of restorations. The thermal expansion coefficients of dental tissues and restorative materials differ. Consequently, gaps that can lead to leakage have been observed. Thermal cycling is one of the most essential artificial aging techniques used in dentistry to test the bond strength of restorative materials to dental tissues. This study aimed to evaluate in vitro the effect of thermal cycling on microleakage in class V restorations restored with different adhesive systems. Methods Standard Class V cavities were prepared on the buccal surfaces of 135 human molars used in the study. Prepared cavities were randomly divided into three groups, with 45 specimens in each group. Universal adhesive, total-etch adhesive, and self-etch adhesive were applied to the groups, respectively. After the restoration procedures were completed, each group was divided into three subgroups. The teeth in these subgroups were subjected to the thermal cycler for 0, 1000, and 10000 thermal cycles. After the coating process, the specimens were incubated in a 0.5% methylene blue solution at 37°C for 24 hours. The prepared specimens were sectioned longitudinally in the buccopalatal direction and examined under a stereomicroscope. Dye penetration between the tooth and the restoration was evaluated according to a scoring table prepared based on studies in the literature. Results It was observed that 10,000 thermal cycle applications resulted in more microleakage than other thermal cycle applications. There is no statistically significant difference in microleakage values between total-etch, self-etch, and universal-etch adhesive systems on occlusal and gingival surfaces at different thermal cycles. The effect of adhesive systems on microleakage on occlusal and gingival surfaces was examined within each thermal cycle group; no statistically significant difference was found between adhesive systems. Conclusions The study results showed no difference in microleakage between the groups. More accurate results can be obtained in predicting the clinical life of restorative materials and in material selection by incorporating similar studies.