Osteoconductive HAp and TiO 2 Coatings on Titanium using Hydro-process
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1236-SS08-23
Osteoconductive HAp and TiO2 coatings on Titanium using Hydro-process 1
Dai Yamamoto1, Kensuke Kuroda1, Ryoichi Ichino2, and Masazumi Okido1 Dept. of Mater. Sci. & Eng., 2EcoTopia Science Institute, Nagoya Univ., Furo, Chikusa, Nagoya, Aichi, 464-8603, Japan
ABSTRACT Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) and titanium dioxide (TiO2, titania) are of interest for bone-interfacing implant applications, because of their demonstrated osteoconductive properties. They were coated on the titanium implants using hydro-processes and investigated the in vivo performance. HAp coatings were formed on cp-titanium plates or rods by the thermal substrate method in an aqueous solution included 0.3 mM Ca(H2PO4)2 and 0.7 mM CaCl2. In the formation of carbonate apatite coating, CaHCO3 was added to the solution, and in HAp/gelatin and HAp/collagen composite coatings, acid-soluble collagen (Type I) was added. The coating experiments were conducted at 313-433 K and pH = 8 for 15 or 30 min. Titania films were formed on the titanium implants by anodizing at < 100 V in 0.1 M H2SO4, H3PO4, and NaOH aqueous solutions at 298 K. The properties for the coated samples were studied using XRD, EDX, FT-IR, and SEM. And the surface roughness of titania coatings was measured. In in vivo evaluations, the coated rod specimens were implanted in rats femoral for 2 weeks, the osteoconduction on them was evaluated. Two weeks postimplantation, new bone formed on the coated and non-coated titanium rods in the cancellous bone and cortical bone, respectively. Bone-implant contact ratio, RB-I, which was used for the evaluation of new bone formation, was significantly depended on the compound formed on titanium implants, and also the coating processes. INTRODUCTION Hydroxyapatite (Ca10(PO4)6(OH)2, HAp), is of interest in bone-interfacing implant applications because of their demonstrated osteoconductive properties. 1) However, biological apatite in natural bone is not in the form of pure HAp, and it usually exists as carbonate apatite (CO3Ap) including some amount of CaCO3 and collagen. CaCO3 has bioactivity such as cell compatibility and hard tissue compatibility.2, 3) It is expected that CO32- influences biological reactivity and osteoconductive properties. Collagen is main organic composition in natural bone. We have considered that collagen might be a precursor of natural bone if it is included in implants. Thermal substrate method is a new technique that overcomes several weaknesses in the traditional hydro-processes of forming HAp4-12). Titania, TiO2, is easily formed on titanium substrate by oxidation. It is reported that TiO2 has high osteoconductivity.13) However, the implant surface roughness affects to the osteoconductivity. Anodizing is a method that can form oxide film keeping the initial surface roughness of substrates. It can be applied to complex-shaped material, which is difficult for other methods to form oxide film uniformly on. In this work, CO3Ap, CO3Ap/CaCO3 composite, and CO3Ap/collagen composite were formed on the titanium su
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