Norihiro Arimoto

Effect of electrochemically deposited apatite coating on bonding of bone to the HA-G-Ti composite and titanium

The surfaces of hydroxyapatite-glass-titanium (HA-G-Ti) functionally gradient composite and titanium bars were treated with electrochemical apatite deposition, and a cathodic current was applied at 62 degrees C in a solution containing calcium and phosphate ions. Specimens with and without the electrochemical surface treatment were implanted in the femurs of Japanese white rabbits. The rabbits were sacrificed at 3, 6, and 9 weeks after implantation, and the bonding strengths of bone to these specimens were determined by a pull-out method. At 3 and 6 weeks after implantation the specimens with the electrochemical surface treatment showed larger values for the Weibull modulus and characteristic strengths than those of untreated specimens, whereas there was no remarkable difference in the results at 9 weeks. Especially the pull-out strengths of surface-treated specimens were significantly larger than the untreated ones at 3 weeks after implantation. Scanning electron microscopy and Fourier transform infrared absorption spectroscopy of the specimen surface after implantation demonstrated that formation of new bone was enhanced by the electrochemical surface treatment. It can be concluded that the electrochemical surface treatment undoubtedly contributes to the early stage fixation between bone and implant.

Effect of electrochemical deposition of calcium phosphate on bonding of the HA-G-Ti composite and titanium to bone

ABSTRACT Calcium phosphates were deposited on the hydroxyapatite-glass-titanium (HA-G-Ti) functionally gradient composite bars as well as pure titanium bars by electrochemical process. After implantation in femur of rabbits, the bonding strengths of the four groups of the specimens to the bone were determined by the pull-out method. At 3 weeks after implantation, the bonding strengths of the composite and of the titanium with the electrochemical calcium phosphate coating were significantly higher than those without it, respectively (p 0.05). These results demonstrate that the electrochemical calcium phosphate coating increases the bonding strength of the implant to bone in the early stages of implantation.

Micro-CT Analysis of New Bone Formation Around Implant with Electrochemically Deposited Apatite

Micro-CT was employed to determine the volume of new bone formed ar ound the implants with and without the electrochemically deposited apatite. With the accumulation of new bone area in the 2-dimensional images, the volumes of new bone around implants were deriv d. Linear regression analysis revealed a correlation ( r=0.704) between the pull-out bonding strengths and the volume of new bone of rabbit femora around the implants. Introduction We reported that the electrochemical deposition of apatite have som advantages: i.e. it can easily create a homogeneous apatite coating on substrates having complicate d sh pes such as dental implants, and requires only simple and small devices. Furthermore , varying the electrochemical conditions can easily control the morphology of deposited apatite [1-6]. The bonding strength of the implant with the electrochemically deposited apatite depended on the morphology of apatite [7, 8]. The apatite deposited at 100 ̊C showed the best bioactivity in vitro [6, 8]. At 3-week implantation, the boundary of the implant coated at 100 ̊C was completely fill d with new bone, whereas that at 200 ̊C was not filled with it [9]. On the other hand, micro-computed tomography (CT) recently is applied to osteology [10-12]. The purpose of the pres ent tudy was to quantitatively determine the volume of new bone formed around the implants with and without the electrochemical apatite coating using micro-CT and to discuss the relation between the amount of new-bone and their bonding strengths. Materials and Methods The electrolyte was heated in stainless steel-autoclave asse mbled two electrodes, a stirring screw, a pressure gauge, a pressure valve, a thermo-couple and an electric hea ter. A platinum plate, 20 x 20 x 0.5 mm, was used as the counter electrode and commercially pur e titanium bars, 2 x 12 mm, were employed as the working electrode. The electrolyte was prepared by dissolving given amounts of reagent-grade chemicals of 137.8 mM of NaCl, 1.67 mM of K 2HPO4, and 2.5 mM of CaCl2·2H2O into distilled water. The solution was buffered to pH value of 7.2 wi th 50 mM tris(hydroxymethyl)aminomethane [(CH 2OH)3CNH2] and an adequate amount of hydrochloric acid. The electrolyte was heated at 100, 150, and 200 ̊C using electric heater and agitated by a stainless screw. The current was maintained at 12.5 mA/cm 2 by DC power supply for 1 hr. After loading of the constant current, the titanium bars loaded as cathodes were r insed with distilled water and dried at 37 ̊C in air. These titanium bars with and without the electrochemically depos it d apatite were implanted into the femora of Japanese white rabbit. The rabbits were sacrific ed at 3 weeks after implantation and the femora were taken out from the bodies. Immediately, the fem ora were used for radiographic Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 611-614 doi:10.4028/www.scientific.net/KEM.240-242.611

Preparation of Hydroxyapatite Fiber by using Alginate and its Application to Bioceramics

ABSTRACT Hydroxyapatite fibers were prepared by a reaction of ion exchange of potassium alginate. To investigate the biocompatibility of the hydroxyapatite fibers, surface changes of these fibers were investigated in vitro and in vivo. In vitro experiment: the fibers were immersed in distilled water and a simulated body fluid (SBF) at 37°C for 9 weeks. After immersion, many voids were observed on the surface of the fibers in distilled water, whereas, the small flake-like particles precipitated on the surface of the fiber and the micro-pores were partially formed around the grain boundary in the SBF. In vivo experiment: diffusion chambers filled with these fibers were implanted in subcutaneous tissue of rats. At 3 weeks after implantation, small pores and granular precipitates were observed on the surface of the fibers covered with fascia. These results suggest that the hydroxyapatite fibers are useful biocompatible ceramics which are especially suitable for filling materials.