Azusa Seki

Formation and in Vivo Evaluation of Carbonate Apatite and Carbonate Apatite/CaCO3 Composite Films Using the Thermal Substrate Method in Aqueous Solution

We have studied the formation and carried out an in vivo evaluation of carbonate apatite (CO3-Ap) and CO3-Ap/CaCO3 composite coatings on titanium substrates using the thermal substrate method. The coatings were formed on commercial pure titanium rods (diameter=2 mm, length=5 mm) and plates (thickness=0.3 mm) by the thermal substrate method in an aqueous solution that contained Ca(H2PO4)2, CaCl2, and NaHCO3. The coating experiments were conducted at 40-140°C and pH=8 for periods of 15 or 30 min. The coating temperature and NaHCO3 of the solution had a significant influence on the surface morphology (net-like, plate-like, needle-like, or sphere-like), the phase (single phase of CO3-Ap or binary phase of CO3-Ap and CaCO3), and the carbonate content in the precipitated films. A subsequent autoclave treatment also had an effect on the films. A coated rod was implanted in a 10 weeks old male rats tibia with a non-coated titanium rod being used as a control. The constructs were retrieved after a period of 14 d postimplantation and examined for new bone formation and for tissue response in the cancellous and cortical bone parts, respectively. Single-phase sphere-like CO3-Ap had high osteoconductivity in the cortical bone region, and this increased with increasing carbonate content in the films. However, the osteoconductivity of the CO3-Ap/CaCO3 composite coatings decreased with increasing total carbonate content.

Osteoconductivity of Titania/Hydroxyapatite Composite Films Formed Using Pulse Electrolysis

Titania (TiO2)/hydroxyapatite (HAp) composite films were prepared on commercial pure titanium rods (2 mm in diameter, 5 mm in length) by anodic-cathodic pulse electrolysis in an aqueous solution consisting of 0.3 mM Ca(H2PO4)2 and 0.7 mM CaCl2 and pH=5.5. The electrolysis was carried out in an autoclave at 120°C for 30 min. using +8.7 V vs. Ag/AgCl sat. KCl as the anodic potential and -9.3 V as the cathodic potential, and changing the electrolysis cycle (60~600 s) and duty ratio. We obtained TiO2/HAp composite films in which fine HAp particles were uniformly dispersed on a thin TiO2 layer. The coated rods were implanted in the tibiae of 10-week-old male rats. The constructs were retrieved 14 d postimplantation and examined for new bone formation and tissue response in the cancellous and cortical bone. They were compared with HAp-coated titanium rods, TiO2-coated rods (anodizing in an aqueous solution), TiO2/HAp-coated rods formed by the high temperature oxidization of specimens coated with HAp by cathodic electrolysis, and uncoated titanium rods. Fourteen days after implantation, new bone had formed on all the coated samples (HAp, TiO2, and TiO2/HAp) and noncoated titanium rods in the cancellous bone and cortical bone. In particular, TiO2/HAp composite films prepared by pulse electrolysis had very high osteoconductivity in the part of cortical bone, which resulted from a synergistic effect of HAp and TiO2 on the bioactivity.