Effect of liquid rubber additions on physical properties of Bis-GMA based dental resins

ObjectiveThe aim of this investigation was to determine the effect of an experimental liquid rubber (LR) toughening agent on fracture toughness, crosslink density and Barcol hardness of polymerized mixtures of 50/50 wt% Bis-GMA and TEGDMA.MethodsAn experimental LR, was added to a solution of Bis-GMA and TEGDMA containing 1 wt% dimethylamino ethyl methacrylate and 0.5 wt% camphoroquinone at concentrations 0–10%. The composites were polymerized by exposure to a visible light curing unit for 60 s. Fracture toughness was determined according to ASTM. 399. Crosslink density was evaluated using a swell test in ethanol.ResultsMean fracture toughness values ranged from 0.39 MPa m1/2 for samples containing 6% to 1.24 MPa m1/2 for samples containing 8% LR. Fracture toughness of samples containing 2%, 4%, and 8% LR were significantly higher than controls. The highest degree of cross-linkage was obtained in controls and lowest for samples containing 2% LR. Barcol Hardness values ranged from 36.7 for the control and 4% LR composition to 31.2 for samples containing 10% LR.SignificanceAddition of 2, 4 and 8% LR increases the fracture toughness of Bis-GMA/TEGDMA composites. Addition of LR shows promise as a method of improving the fracture toughness of Bis-GMA based dental composites.