Degree of conversion of luting cements under fiber-reinforced composite resins

The mechanical properties and clinical performance of cements are affected by their degree of conversion; inadequate polymerization may lead to failures. this study evaluated the polymerization proportion of a dual-cure luting cement beneath two different fiber-reinforced composite restorations of various thicknesses utilizing a degree of conversion (dc) technique. two types of glass fiber (gf); everstick (stick tec,turku,finland) and vectris frame (ivoclar,vivadent schaan,liechtenstein) were used to prepare laminate veneer simulations. the polymerization course of the composite resin luting cement (rely x arc/3m-espe) was investigated using fourier-transformed infrared spectroscopy (ft-ir) to evaluate the quantity of remaining carbon-carbon double bonds in the specimen beneath two types of fiber-reinforced composite restorations of three thicknesses. the polymerization proportion of rely x arc cement beneath everstick-reinforced composite restorations was similar to the composite-only group (p>0.005) at 0.5-,1-,and 1.5-mm thicknesses after the light-curing period (40 sec) utilizing the dc technique. the polymerization proportion was decreased when the thickness (1 and 1.5 mm) of vectris frame was increased (p<0.005). the polymerization process was continued using the auto-polymerization mechanism after 1020 sec,but the 1.5-mm vectris frame-reinforced composite group exhibited the lowest polymerization proportion of all groups (p<0.005). in conclusion,an increased thickness of fiber-reinforced composite resin may negatively affect the polymerization proportion of the underlying resin cement,depending on the fiber material used.