In vitro and in vivo studies of alkali- and heat-treated Ti-6Al-7Nb and Ti-5Al-2Nb-1Ta alloys for orthopedic implants.

In vitro studies of Ti-6Al-7Nb and Ti-5Al-2Nb-1Ta alloys were carried out by treating the specimens with 10 M NaOH at 60 degrees C for 24 h and subsequently heat-treated at 600 degrees C for 1 h. After the alkali and heat treatments, and on subsequent soaking in simulated body fluid (SBF), the morphological and compositional changes on the surface of the specimens were examined using scanning electron microscope attached with an energy-dispersive electron probe X-ray analyzer. The results revealed a dense and uniform bonelike apatite layer on the surface of treated substrates immersed in SBF solution. In vivo studies were carried out in rats to evaluate osteoconduction of Ti-6Al-7Nb and Ti-5Al-2Nb-1Ta alloys surface after alkali and heat treatments compared with untreated titanium alloys as the control. The following titanium implants were prepared from these species: (1) control without implant; (2) untreated titanium implant; (3) alkali- and heat-treated implant--the implants were immersed in 10 M NaOH solution at 60 degrees C for 24 h and subsequently heated at 600 degrees C for 1 h. The specimens were inserted into the medial side of each tibia of rats. Histologically, direct bone contact with the implant surface was significantly higher in the alkali heat-treated implants than the untreated titanium implants.