Previous studies on phosphide and oxide films formed by heat treatment of Ti dip-coated with HA showed various properties in both composition and morphology of the interfaces according to the heating temperature. HA dip-coated Ti screws were heated for 1 hour in a graphite furnace with a protective argon atmosphere at 800 (TiP1), 850 (TiP2) and 900°C (TiP3), after producing a vacuum (10-2 Torr). The adhering HA layers on the metal surfaces were removed with a strong jet of distilled water and subsequently sterilized according to standard procedures for metallic implant devices. Nine adult New Zealand white rabbits, aged 9 to 10 months, were used in the experiments. The three screw-shape specimens including an untreated Ti (c. pTi) screw were implanted in each animal, two in each medial proximal tibia according to the surgical protocol of the Branemark implant system. After 4 weeks, the rabbits were sacrificed with a lethal dose of pentobarbital injection and then the osseointegration was determined by an immediate measurement of the removal torque of the specimens. The results obtained demonstrated that the phosphide and rough Ti surface layers yielded higher removal torque values than the untreated Ti surface. The mean torques were 15.3, 33.8, 27.7 and 37.5 N-cm for c. pTi, TiP1, TipP2 and TiP3, respectively. Oxide thickness and mean pore size of the heated Ti surfaces increased relative to elevated heating temperature, the maximum phosphorus concentration (about 7 at. %) diffused from the HA layer was obtained via heating at 800°C. From these results, it can be concluded that the chemical composition of Ti phosphide layer and the surface morphology of Ti-based materials play an important role in the bone bonding process on Ti implants.

Keywords: Titanium, hydroxyapatite, Surface Modification, Bone Bonding, Titanium Phosphide