CYCLE FATIGUE OF HYDROXYAPATITE-COATED TITANIUM-ALLOY IMPLANT MATERIAL - EFFECT OF CRYSTALLINITY

Titanium alloy (ASTM F-136) rods were coated with hydroxyapatite (HA) of 3 levels of crystallinity, which were determined by X-ray diffracti on (XRD) analysis to be 60.5%, 52.8%, and 47.8%. Fourier Transform Inf rared (FTIR) spectroscopy analysis showed the removal of the hydroxyl and carbonate groups as compared to the original HA powder. It appears that these changes are caused by the high temperature plasma spray co ating process. Cyclic fatigue testing in a lactated Ringer's solution to 5 million cycles showed no statistical difference in calcium dissol ution among the 3 crystalline levels, whereas phosphorus dissolution w as lowest from the highest crystalline coating sample. The mechanical properties, however, did not change in response to fatigue loading.