AbstractsBiology & Animal Science

One of the most important factors for a successful performance of a load-bearing implant for hard tissue replacement is its mechanical compatibility with human bone. That implies that the stiffness should be close to that of a bone and the strength of the implant material must be high enough to bear the load applied under physiological conditions. The Young´s modulus of most of the commonly used biomedical alloys is larger than that of a human bone (around 100 GPa for cp Ti, 112 GPa for Ti-6Al-4V versus 10-30 GPa for cortical human bone). A stiffness reduction of Ti alloys can be achieved by two approaches: (i) selecting an alloy composition with low Young´s modulus i.e. a ß-type alloy and (ii) introducing a reasonable amount of porosity. The composition of Ti-40Nb was chosen for the present work, as it allows to stabilize a single ß-type phase with low Young´s modulus at room temperature. The samples were produced by a powder metallurgical approach. The Ti-40Nb alloy powder was obtained by ball-milling of elemental Ti and Nb powders. The influence of the milling parameters on the oxygen content in the milled powder was studied. Powders with a lowest oxygen content of 0.4 wt.-% had an almost single ß-type phase after heat treatment and quenching. Porous samples were produced by loose powder sintering, hot-pressing and sintering with NaCl as a space-holder. The influence of the different processing routes and different porosities on the mechanical properties of the alloy was studied. The samples produced by loose powder sintering had mechanical properties close to those of cortical human bone (Young´s modulus 20 GPa, compression strength 150 MPa) and the samples produced by loose sintering with space-holder materials had mechanical properties close to those of human spongy bone (Young´s modulus 0.2-2 GPa, compression strength 50 MPa). Porous Ti-40Nb samples were coated with bone-like hydroxyapatite by an electrochemical deposition method in order to improve the osseointegration of the samples with bone tissue. The experiments were carried out with samples produced by different routes and a correlation between the deposition parameters and the morphology of the hydroxyapatite needles was found.