The effect of the elastic modulus of low-viscosity resins on the microleakage of Class V resin composite restorations under occlusal loading.

This study aimed to evaluate the effectiveness of various intermediate layers on the microleakage of Class V restorations under an occlusal load. Wedge-shaped cavities were prepared on the buccal surface of 72 extracted premolars, which were then treated with an adhesive system (One Up Bond F Plus), divided into three groups, and restored with: 1) Estelite Sigma resin composite, 2) a resin composite with Low Flow flowable composite, or 3) a resin composite with High Flow flowable composite. The specimens were subjected to a nano-indentation test to evaluate the elastic modulus of successive layers at the resin-dentine interface and were subjected to a microleakage test under either unloaded or loaded conditions. The elastic moduli were significantly different among substrates (p<0.05), except between the hybrid layer/Low Flow and the hybrid layer/High Flow. The elastic moduli of the Low Flow composite were higher than those of the High Flow composite. Occlusal force increased dentine leakage in the group that was restored without flowable composites.