Bioactive tantalum metal prepared by NaOH treatment

Untreated tantalum metal formed an apatite on its surface in simulated body fluid (SBF) with ion concentrations nearly equal to these of human blood p lasma. However, it took an induction period as long as 4 weeks for apatite formation. The tantalum metal formed the apatite within 1 week when it was previously soaked in a 0.2 or 0.5M NaOH aqueous solution at 60 degrees C fo r 24 h to form a sodium tantalate hydrogel layer on its surface. The decrea se in the induction period of apatite formation was attributed to the catal ytic effect of the Ta-OH groups on the surface of the tantalum metal for ap atite nucleation and acceleration of the apatite nucleation by an increased ionic activity product of the apatite in the fluid due to the release of N a+ ions. The NaOH-treated tantalum metal can form apatite in a short period even in the living body and bond to the bone through this apatite layer. T his indicates that a highly bioactive tantalum metal can be obtained by a s imple chemical treatment. (C)2000 John Wiley & Sons, Inc.