Effect of Cobalt-Chromium Alloy Surface Casting on Resistance to Deflection Fatigue and Surface Hardness of Titanium

This study investigated the resistance to deflection fatigue and surface hardness of grade 2 titanium bar samples to a protion of which a layer of cobalt-chromium alloy was cast under standard dental laboratory conditions. The uncovered part of the titanium bar was deflected, and the number of loading cycles required to cause a fatigue fracture in the titanium bar was recorded. The Vickers hardness of the titanium bar was measured, and the fracture surface was examined by scanning electron microscope and energy-dispersive spectroscopy. The number of loading cycles was considerably lower in bars with the cobalt-chromium surface cast (83 vs. 13.770 cycles) (P .001), while the surface hardness of the titanium bar with the cobalt-chromium surface cast was higher than that without the surface cast (Vicers hardness number 329 vs. 178) (P .001). These findinfgs suggest that the cobalt-chromium surface cast dramatically affects the fatigue resistance of pure titanium, which should be considered when novel implant-supported prostheses made from premanufactured titanium parts are planned.