Properties of functionally gradient composite consisting of hydroxyapatite containing glass coated titanium and characters for bioactive implant

Composites comprising hydroxyapatite (HA) containing glass layer and pure titanium or Ti-6Al-4V alloy, so called HA-G-Ti functionally gradient materials, have been shown to be useful for bioactive artificial joints and dental implants. In the present study, the mechanical and thermal properties of the HA containing glasses were examined. The compressive strength of HA containing glasses less than 70 wt% HA content was sufficiently larger than that of bone. The hardness of about 70 wt% HA containing glass corresponded to that of natural teeth. It has been found from DSC analysis that the glass little reacts with HA at firing temperature (950°C). Thermal expansion coefficients of HA containing glasses with relatively low HA content were suitable values for the coating on Ti and Ti-6Al-4V. The bonding strength of the glass to Ti substrate reached the maximum value of 28 MPa under the condition of 2.3 μm in surface roughness (center line average). The HA-G-Ti composites with bioactive surface, etched in a mixture of HF and HNO3, showed a good apposition to the bone in vivo.