Abstract
The effects of metals and the surface roughness of metal on mode I fracture toughness at opaque porcelain/metal interface were investigated using an An-Pt precious alloy, two Au-Pd and Pd semiprecious alloys and a Ni-Cr nonprecious alloy as metal. The variations in surface roughness were obtained by various methods of fusing porcelain to the surface of metals, such as sandblasting (50 and 125 μm), emery paper (#40) and retension beads (100 μm). The major findings were as follows.In all metals used, it was found that the interfacial fracture toughness at the process of crack propagation was constant. The value of interfacial fracture toughness of the nonprecious alloy, GIC=18.5 J/m2, was about 14 to 20% larger than those of three other alloys used. On the effect of surface roughness, it was found that larger quantities of foamy opaque porcelain remained on the metal surface as the surface roughness increased.The interfacial fracture toughness after emery paper treatment was only about 10% greater than that of sandblast treatment, however, that after retention bead treatment showed a three-fold increase.Therefore, the retention bead treatment was very effective. It was recognezed that the method of determining mode I interfacial fracture toughness used in this paper was more effective for evaluating the interfacial property of dental materials.
