Two methods for measuring shear strengh 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 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 specimen and the values obtained with the cube/cube specimen scemed to depend on the quality of the porcelain work. It seem questionable whether “bone strenghth values” as obtained with these two methods can be the basis for requirenments in a standard for porcelain-metal systems.

Bond strength of porcelain to dental alloys – an evaluation of two test methods
Øilo G, Johansson B, Syverud M
European Journal of Oral Sciences 1981; 89 (3): 289-296DOI 10.1111/j.1600-0722.1981.tb01685.x