Use of Wollastonite in a Biomimetic Method to Promote Apatite Formation on a Co-Cr-Mo Alloy

Wollastonite ceramics was used in a biomimetic method to promote apatite formation on a Co-Cr-Mo alloy (ASTM F-75). The metallic samples were initially chemically treated in a 5M NaOH aqueous solution. The treated samples were immersed for 7 days in SBF on a bed of wollastonite and then immersed 7 or 14 days in 1.5SBF. For comparative purposes no wollastonite was used during the first 7 days in some tests. A homogeneous bonelike apatite layer was formed on the samples immersed in SBF on the wollastonite bed. The morphology and the Ca/P ratio of the layer were closely similar to those observed on the existing bioactive systems. A thinner homogeneous bonelike apatite layer was formed on the samples immersed in SBF and 1.5SBF without using wollastonite. However, the morphology and the Ca/P ratio of this layer differs slightly to that observed on the existing bioactive systems. The immersion of the samples during the first days in SBF on a wollastonite bed improves significantly the quality and thickness of the bonelike apatite layer.