Construction Of Bioactive Hierarchical Porous Coatings On Titanium Surface By Mixed-alkali And-heat-treatment

Considering the shortage of bioactivity in oral implants, sandblasted（mechanical treatment） and acid etched（chemical treatment） was used as the pretreatment on titanium with smooth surface, following with alkali-heat-treatment which constructs bioactive coatings adhered strongly on the titanium. The microstructures, chemical and mechanical properties of titanium surface with different methods treated were studied by the scanning electronic microscope（SEM）, energy dispersive spectrometer（EDS）, focused ion beam（FIB）, x-ray diffraction（XRD）, x-ray photoelectronic spectroscopy（XPS）, confocal laser scanning microscopy（CLSM）, contact angle analyzer, stretch experiment and Nanohardness tester. Mixed-alkali（Na OH and Ca（OH）₂） was innovatively used in alkali-heattreatment, specimens after mixed-alkali-heat-treatment, specimens after following heattreatment and specimens after following vapor treament with smooth comparison were immersed in SBF for the constructing of apatite coatings. The faster the HA coatings were built, the more bioactive the specimens were, SEM, EDS and XRD were used to investigate the apatite coatings.Valleys with sharp edge were constructed by SAN on the smooth surface of titanium, then micro-porous topography was built by SLA. After mixed-alkali-heat-treatment, hierarchical micro-nano porous was structured on titanium surface. A small number of SiO₂ particles were left on the surface of SAN, while no SiO₂ was left after SLA. Ca TiO₃, Na₂TiO₃ and Brookite compose the gel layer that adhere to micro-porous topography of specimens after mixed-alkali-and-heat-treatment. A small number of crystal Ca TiO₃ were found embedded in micro-porous topography on the titanium surface. Comparing the difference between samples of mixed-alkali-and-heat-treatment, the fewest crystal Ca TiO₃ were found on the surface of the most dilute mixed-alkali-and-heat-treated titanium（Ti-NC-1）, while Ti-NC-1 performed the best when inducing apatite in SBF. Apatite spheres were found on the surface of Ti-NC-1 after 3 days’ immersing, and TiNC-1 was totally covered by apatite after 7 days’ immersing. While the bonding strength of coatings and substrate on Ti-NC-1 was larger than 31.87±2.70 MPa, Ti-NC-1 was covered by bioactive coatings with strong integration. There is tight crystal coherence relationship between Ca TiO₃, Brookite and apatite, it’s exactly the relationship brought these two phases fabulous ability when inducing apatite.More crystal Ca TiO₃ were found on titanium surface after the following heat treatment, for the reason that gel-state Ca TiO₃ transformed into crystalline state in the heat treatment progress. Gel-state Na₂TiO₃ also turned into crystalline state. The apatite forming ability was badly damaged by these crystal phases. Micro-porous topography turned thick because of the vapor treatment, crystallinity of the phases on titanium surface was also enlarged, accompanied with the bad performance when inducing apatite.