Effect of Composite Resin Preheating on Microleakage in Class V Restorations

Introduction: Microleakage around restorative margins has always been a concern in various clinical conditions. To reduce the effects of microleakage in restorations, various techniques such as composite preheating and immediate or delayed curing are utilized. However, limited and contradictory studies have been conducted on the effect of preheating on microleakage and marginal adaptation of Class V composite restorations. Therefore, this study aimed to evaluate the effect of preheating on microleakage in Class V restorations and to compare it with the standard technique (sandwich technique). Materials and Methods: This experimental study included fifty healthy premolar teeth, on which Class V cavities were prepared on the buccal and lingual surfaces. The samples were then divided into four groups, each consisting of 25 teeth. The first group (G1, control) was restored with composite resin. In the second group (G2), cavities were restored with composite resin preheated to 68°C. The third group (G3) had cavities restored with composite resin preheated to 68°C, followed by delayed curing for 15 seconds. In the fourth group (G4), cavities were restored using the sandwich technique (RMGI + composite). After thermocycling, the teeth were immersed in a methylene blue solution for 24 hours. The samples were then sectioned buccolingually, and microleakage was assessed under a stereomicroscope. The findings were analyzed using the Kruskal-Wallis and Mann-Whitney tests. Results: The average microleakage on the gingival side was highest in group G4 (2.44±1.16) and lowest in group G3 (0.32±0.63). A statistically significant difference in average microleakage was observed between the groups (p<0.001). The Mann-Whitney test results indicated statistically significant differences between all pairwise group comparisons, except between G1 and G3 (p<0.001). Conclusion: Preheating improves the adaptation of composite resin and reduces microleakage. The use of an RMGI liner did not reduce microleakage. Delayed curing diminishes the positive effects of preheating on microleakage.