MATERIALS FOR ORTHOPEDIC APPLICATIONS - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 88

lated body fl uid. The alloy compounds were surface treated by HNO 3 and NaOH
aqueous solutions, prior to immersing in SBF. It was found that an HAp layer
formed on the surface of the NiTi alloy after immersing 48 hours inside SBF. The
surface modifi ed and as received NiTi cylindrical implants were bilaterally im-
planted into the femurs of rabbits. It was observed that HAp coating can facili-
tate fast proliferation of osteoblasts. Direct bony coverage of the surface-modi-
fi ed NiTi implants at six weeks of implantation was monitored. After 13 weeks of
implantation, the interface between the coated implant and the bone shows
the nature of osteo-bonding. On the other hand, the interface between the un-
coated implant and the bone has gaps, showing a weak bone-implant interface
(Figure 3.15 ).
(a)
(b)
Figure 3.15. The morphologies of surface of implants after 13 weeks of implantation. (a) A
little bulged cell and collagen fi brous on uncoated NiTi implant. (b) A large number of bone
cells and collagen fi brous networks on coated NiTi implant 127 .