Abstract
The fracture toughness of four dental filling cement products was examined using a single-edge notched(SEN)specimen.The validity as plane-strain fracture toughness of the obtained fracture toughness and the effect of fracture toughness on storage in distilled water at 37℃ were discussed.Kc- B/(Kc/σt)2 curves obtained from fracture toughness tests on specimens with various thicknesses did not reach a constant and the thickness at which the curves leveled off could not be determined, B/(Kc/σt)2 having 1.0〜4.0. Many fracture toughness values obtained from a SEN specimen(thickness B=5.0 mm, width W=5.0 mm and crack length a=W/2)were declared invalid as a plane-strain fracture toughness according to ASTM E399. The mean fracture toughness of four products after storage for 30 days in distilled water at 37℃ decreased to about 75% of the fracture toughness for 24 h specimens.
