The purpose of the present study was to evaluate the effect of filler loading on the fracture toughness of light-cured dental resin composites (DRCs). The monomer Bis-GMA and TEGDMA (75/25 wt/wt) were mixed with treated micro-sized aluminum oxide (Al2O3) particles ranging from 40-60 wt% as filler. The composite samples were cured with LED for 80s. The bulk density (g/cm3) and apparent porosity (%) of the samples were determined according to the ASTM standard. The fracture toughness (KIC) values of the composites were determined using a single edge notched specimen in the three-point bending test. There was a significant difference in KICof the composites with different loading of Al2O3particles (p< 0.05). The highest amount of filler (60 wt%) reduced the KICvalue to 1.5 MPa.m1/2. As a conclusion, the Al2O3particles used as filler loading does have an effect on the mechanical properties of DRCs.
