Surface Of The Titanium Surface Of The Titanium Oxide Film, Calcium And Phosphorus Characterization Titanium Biological Activity

The Biological properties of titanium implant depend on its surface oxide film. Because the natural oxide film is bioinert, titanium is generally bioactivated by modifying oxide film or coating Ca-P layer. However, the knowledge on relationship between bioactivity and surface characterization of titanium, i.e., the bioactivating mechanism of titanium has been insufficient yet. In this paper, rutilt oxide film, anatase oxide film on titanium, titanium surfaces containing calcium and containing phosphorus, and apatite coating-Ti were surface characterized. Based on investigation on apatite precipitation, protein adsorption and osteoblast culture in vitro on the titanium surfaces, the relationship between the bioactivity and the surface characterization of titanium was studied.The surface rutile oxide films and anatase oxide films on titanium were obtained by heat-treatment in different oxidation atmospheres and acid-etching respectively. The bioactivity of oxide films was investigated by immersion test in a supersaturated calcium phosphate solution. The results indicated that the bioactivity of titanium was independent on crystal phases of the oxide films, and was related to surface hydroxyl groups and surface energy. Compared to surface acidic hydroxyl groups, basic hydroxyl groups had more contribution to the bioactivity of titanium. In the protein adsorption and osteoblast culture in vitro, more surface hydroxyl groups and higher polar component of surface energy led to more protein and cell adsorbed, and higher cellular activity. The enhancement of the surface roughness also increased the apatite precipitation and the adsorption of the protein and the osteoblast. Both calcium and phosphorus on the surface layer induced the precipitation of apatite on titanium. This is attributed to more surface hydroxyl groups on the surfacescontaining calcium and phosphorus than tatinium surface and stong chemical reaction of calcium or phosphate on the surfaces with phosphate or calcium in the simulated biological environment. But calcium and phosphate precipitated more rapidly on the surface containing calcium and formed more uniform Ca-deficient carbonate apatite coating than on the surface containing phosphorus. On the surface containing calcium, the precipitation of phosphate ions was prior to calcium ions due to a number of the surface calcium ions and the surface positive charge; on the surface containing phosphorus, the precipitation of calcium ions was prior to phosphate ions. The more protein and osteoblast adsorbed on the surface containing calcium. The activity of cell adsorbed on the surface containing calcium was higher than that containing phosphorus. This is possible because the surface containing calcium with positive charge was more beneficial to the adsorption of bovine albumin serum and the ligant proteins of cell onto the surfaces. The state of the protein and the behavior of cell adsorbed on the surface containing calcium were similar to those on aptite coating. Thus, compared to phosphorus, calcium play more important role to the activity of titanium.In addition, heat-oxidation in water vapor before the preparation of the surface containing calcium enhanced the bond-strength of the coating to the substrate. This is probable attributed to the larger amount of the surface hydroxyl groups and higher surface energy leading the higher reactivity after the treatment in water vapor.