Bond strength of porcelain to dental alloys - an evaluation of two test methods.

Two methods for measuring shear strength of the porcelain-metal interface, a rod/disk-push test and a cube/cube-push test, were compared using the same metals and porcelain material. Both types of specimen showed evidence of complex stress distribution at the interface during loading and a fracture line located mainly in the opaque porcelain layer. Both methods were thus mainly a test of the "strength" of the porcelain at the interface. The "bond strength values" obtained with the rod/disk specimen seemed to depend on the geometry of the specimen and the values obtained with the cube/cube specimen seemed to depend on the quality of the porcelain work. It seems questionable whether "bond strength values" as obtained with these two methods can be the basis for requirements in a standard for porcelain-metal systems.