Objective: The aims of this investigation were to investigate the effect of thermocycling on the marginal gap formation of composite inlays using three types of luting cements (Compolute, PermaCem, Fuji Plus, Panavia 21: as a control) and on mechanical properties of four luting cements.
Methods: The maximum marginal gap in the dentin cavity of each of ten resin inlay specimens in each group, was measured by a microscope before and after 10,000 thermocycles. The dimensional change, shear bond strength to dentin, and material and conditions for flexural strength and modulus testing were examined.
Results: Compolute and Panavia 21 showed marginal gaps of approximately 10 microm before thermocycling. In contrast, the gap widths after thermocycling was significantly wider. Although the gap widths of PermaCem and Fuji Plus were approximately 60-110 microm prior to thermocycling, they were significantly smaller in width after thermocycling. Statistical differences in the shear bond strength to dentin were not observed before or after thermocycling for all materials. The flexural strength and modulus were significantly increased after thermocycling compared with three products and with all four products, respectively.
Significance: The mechanical properties of all four luting cements were closely related to their marginal gap formations and these mechanical factors have important roles in determining their marginal gap formations.