Bioactivation of titanium using calcium-hydroxide slurry

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The activation of osteogenesis on titanium has been a major interest for biomaterial researchers, and, thus, various surface modification techniques have been studied. Among these techniques, a hydroxyapatite (HAP) coating applied by the plasma-splaying process is the most successful technique due to its good biomaterial-bone fixation ability and HAP-coated titanium is currently used in clinical settings. However, dentists and orthopedists have pointed out that fracture at the HAP-titanium interface and dissolution of the coating itself sometimes occur after such implants have been in the human body for a long time. We recently developed a chemical coating technique using calcium-hydroxide slurry. The process is as follows: a titanium substrate is buried in calcium-hydroxide slurry prepared by a mixture of calcium-hydroxide powder with water, and, subsequently, the slurry containing the titanium substrate is heated in air. We revealed that, by treating a titanium plate with this proces … More s, a calcium titanate coating was formed on its surface. In the present study, the relationships between the treatment conditions and the characteristics of the surface layer were investigated. Furthermore, the surface-modified titanium rod was surgically inserted in hard tissue of rat, and osteogenesis around the rod was investigated.We initially investigated the effect of heating temperatures in the slurry processing upon characteristics of the coatings. When using the heating temperature beyond 600℃, a crystallized calcium titanate coating was formed on its surface, and the coated titanium can precipitate calcium phosphate in a simulated body fluid rapidly. When raising the temperature, thick titanium dioxide layer was simultaneously formed on the substrate, resulting in the decrease of the adhesion strength of the coating. We secondly attempted to improve biocompatibility of the coating by adding sodium ions in the slurry. When preparing the slurry by mixing Ca(OH)_2 with 1-M NaOH or NaCl solutions, a composite coating comprising calcium and sodium titanates were formed on the substrate. The composite coating could precipitate calcium phosphate more rapidly, although mechanical strength of the coating would decrease owing to the formation of the thick coating. Last, we surgically implanted the Ti rod treated with the Ca(OH)_2 slurry and with the heating temperature of 600℃, into a rat. At 7 days, new bone was formed vigorously and was in contact with the surface directly. Less