Abstract
Fracture toughness(KIC), a useful indicator of marginal fracture resistance and wear resistance which are important properties for dental composite resins, was measured. Six visible light cured composites with different filler contents (0-64 vol%) were prepared experimentally. Fracture toughness, compressive prool strength, diametral tensile strenght, bending strength and bending elastic modulus of these composites were measured. Single edge notched three-point bending specimens were employed for fracture toughness measurement. Fractography was performed on the tested specimens by scanning electron microscopy. A positive correlation against volume filler content was obtained for every mechanical property. Fracture toughness (KIC) of the unfilled resin and the composite resin with 64 vol% filler were 0.604 MPa √m and 1.409 MPa √m, respectively. The reinforcement effect of filler compound was greater in low filler content composites (0-30 vol%) than that in high filler content composites (30-64 vol%). Interestingly, other mechanical properties did not show this tendency. Increase of surface energy, absorption of fracture energy by small crack formations and crack-pinning effect by filler particles are considered to contribute to the fracture toughness of particle reinforced composites.
