The effect of fiber reinforcement and composition of the overlying composite on the flexural strength of three laboratory-processed fiber-reinforced Composite resins

Reinforcement with fiber is one of effective methods for improvement in flexural properties of indirect composite resin restorations. The composition of the overlying veneering composite plays a critical role in the flexural properties of the final fiber reinforced restoration. The aim of this in-vitro study was to evaluate the effect of fiber reinforcement on the flexural strength of three laboratory-processed fiber-reinforced composite resins. In this experimental-laboratory study, 72 bar type specimens (3×2×25 mm) were constructed by using three types of fiber-reinforced composite resins (Gradia, Signom, Bellglass) and one Plexiglas mold. In each type of composite resin, two groups (one with fiber and one without fiber) were constructed. These specimens were tested by the three-point bending method to measure flexural strength. Data were statistically analyzed with two way ANOVA, Tukey and T-test at 0.05 significance level. The mean flexural strength of Gradia with fiber was higher than the other groups (150.14 MPa) and the mean flexural strength of Signom without fiber was the least (60.53 MPa). There was a significant difference between the mean primary fracture force in the three groups (P<0.001). Within the limitations of this study, it may be concluded that reinforcement with fiber considerably increases the fracture resistance of composite specimens and the overlying veneering composite may play an important role in the transverse strength of fiber reinforced composite specimens.