Hardness and Fracture Toughness of Commercial Core Composite Resins

Abstract

One important mechanical property of core composite resins is fracture toughness, K_IC, which expresses serviceability in the oral cavity, such as the resistance to marginal fracture. K_IC values of eight commercial core composite resins were examined by the single-edge notched-beam (S.E.N.B.) method. Two composites containing about 80wt% Si₃N₄ fillers exhibited both the highest K_IC value of around 2.0MN⋅m^-3/2 and the highest hardness value. The other six composites containing 66 to 86wt% SiO₂-based fillers had K_IC values of around 1.2 to 2.0MN⋅m^-3/2, and there was a tendency toward higher K_IC values as hardness increased. It was speculated that the clinical acceptability of core composite resins could be broadened, if dental clinicians selected composites with higher K_IC values.