Shinji Takemoto

In vivo evaluation of bone-bonding of titanium metal chemically treated with a hydrogen peroxide solution containing tantalum chloride.

Apatite formation on implants is important in achieving a direct bonding to bone tissue. We recently showed that titanium metal chemically treated with a hydrogen peroxide solution containing tantalum chloride has the ability to form a hydroxyapatite layer in simulated body fluid which had inorganic ion composition similar to human blood plasma. In this study, a pure titanium cylinder (4.0 mm in diameter, 20.0 mm in length) treated with this method was implanted into a hole (4.2 mm in diameter) in a rabbits tibia. After implantation for predetermined periods up to 16 weeks, the specimens were extracted with bone tissue, and were examined by push-out test to evaluate the shearing force between the implant and bone tissue. The results were compared with those of non-treated pure titanium. Eight weeks after surgery, the shearing force of the treated titanium implanted in the 4.2 mm-hole was significantly higher than that of non-treated titanium, although the surface roughness was not changed after the treatment. Scanning electron microscopic (SEM) observation and energy-dispersive X-ray (EDX) microanalysis showed that the bone comes very close to the surface of the treated titanium. Moreover, the shearing force was higher for the implanted sample in the 4.0 mm-hole than that in the 4.2 mm-hole. Thus, it is confirmed that the treatment with hydrogen peroxide solution containing tantalum chloride provides higher bonding ability on titanium implants in vivo.

Platelet Adhesion on Metal Oxide Layers

This study was concerned with blood compatibility of titanium oxide lay rs on stainless steel. The titanium oxide layers were prepared through sol-gel pr ocess by dip-coating of tetraethyltitanate solution and heated at 500 °C. The crystal phase, thickness and wettability of the oxide were characterized. The blood compatibility was evaluated in t rm of platelet adhesion using human platelet rich plasma. Consequently, with increase in the thickne ss of the titanium oxide layers, the number of platelet adhered on the stainless steel coated with t itanium oxide layer decreased rapidly. When the thickness of titanium oxide layers on stainless s t el grew more than 150 nm, the number of adherent platelets decreased less than 10% in comparison wit h that on non-coated stainless steel. The titanium oxide layers indicated to be more hydrophilic t an non-coated stainless steel. In conclusion, the thicker and more hydrophilic titanium oxide layer on stainl ess steel appears to inhibit platelet adhesion.

Apatite Formation on Electrochemically Treated Titanium

A titanium oxide gel was electrochemically prepared on Ti with a cell consisting of Ti as the working electrode, Pt as the counter one, AgCl as the reference one, and an aqueous solution of 0.1 mol/L Ca(NO(3))(2) as the electrolyte solution. The Ti electrode was kept at 9.5V for 1 hr for oxidation and subsequently kept at-3.0V for 10 min (Ca9.5-3.0):calcium ions were expected to be adsorbed at the latter treatment. Other Ti specimen was kept at -3.0V for 10 min (Ca-3.0). Both specimens were found so bioactive as to deposit apatite in 12 hr (Ca9.5-3.0) and in 1 day (Ca-3.0) when soaked in a simulated body fluid (Kokubo solution). Calcium carbonate detected on the surface of Ca9.5-3.0 caused no harmful effects on spontaneous deposition of apatite in the fluid.