[Mechanical properties of metal-ceramic systems from nickel-chromium and cobalt-chromium alloys].

BACKGROUND/AIM Metal-ceramic bond strength and alloys' elastic modulus clearly determine the potential of alloy application, because the ceramic integrity during mastication depends on these two characteristics. The aim of this study was to evaluate metal-ceramic bond strenght and elastic modulus of cobalt-chromium alloys in making porcelain-fused-to-metal restorations, regarding the application of the most frequent nickel-chromium alloy. METHODS The research was performed as an experimental study. Six metal-ceramic samples were made from nickel-chromium alloy (Wiron 99) and cobalt-chromium alloy (Wirobond C), according to the manufactures manuals and instructions from ISO 9693: 1996. Three-point bending test was performed up to the ceramic fracture. The fracture load was measured on an universal testing machine (Zwick, type 1464), with cross-head speed of 0,05mm/min. RESULTS The results of this study confirmed the significant differences between the metal-ceramic bond strength (p < 0.01) and elastic modulus (p < 0.001) of nickel-chromium and cobalt-chromium alloys, where cobalt-chromium alloys showed higher values for both tested parameters. CONCLUSION Cobalt-chromium metal-ceramic alloys can successfully replace nickel-chromium alloys, especially for fabrication of long-span metal-ceramic bridges due to the great flexural strength.