Key Engineering Materials Vols. 284-286

Abstract: 60CaO-30P2O5-7Na2O-3TiO2 (mol%) glass-ceramic can be strongly joined with a new β-type Ti-29Nb-13Ta-4.6Zr alloy. In the present work apatite-forming ability in simulated body fluid of the glass-ceramic-coated titanium alloy was enhanced by autoclaving in water at 120°C for 1 h; surface of the autoclaved coating was completely covered with apatite after 10 days of soaking. In vivo tests showed that the glass-ceramic-coated titanium alloy after autoclaving in water makes a strong bond to natural bone.

Abstract: Plasma-sprayed HA coating combines the strength of the metal and the bioactivity of the HA. However, this method has several disadvantages. Alternatives to the plasma-spray method such as electrochemical deposition (ECD) and biomimetic or precipitation methods are being explored. The purpose of this study was to develop an ECD method for coating Ti alloy substrate with different calcium phosphates (octacalcium phosphate, calcium deficient apatite, carbonatesubstituted apatite, fluoride-substituted apatite). Pairs of Ti6Al4V plates that have been mechanically polished, ultrasonically cleaned, acid etched, rinsed and dried were used as anodes and cathodes. ECD was carried out using programmed pulse time electric fields. Results showed that uniform coating with only the desired calcium phosphate can be obtained using metastable calcium phosphate solutions at different pH and temperature conditions and different electrolyte concentrations. Coating thickness varied with the duration of coating deposition. Crystal size varied with other ECD conditions (e.g., pulse time, current density). This method can be used to obtain uniform coating of the desired calcium phosphate composition at low temperatures (25 to 80oC) on substrates of any type of geometry.

Abstract: In this study, the bioactivity of a new kind of anodic oxidized titanium metal was investigated in vitro and in vivo. After immersed in SBF solution for 7 days in vitro, apatite formed and covered almost all the surfaces of the anodic oxidized samples. In vivo animal experiment, the apatite was also tested precipitated on the interface of tissue/materials after 12 weeks post-operation, and there were no any fibrous capsule formed around the materials. The materials bonded with the bone very tightly and attached to the skin very closely, which would result in the achievement of the biological sealing for the bone-anchored percutaneous implants. These positive results might be contributed to the precipitated apatite layer formed on the surface of the bioactive oxidized titanium. Thus, Anodic oxidation treatment might be an effective way to prepare bioactive Ti both for bone replacement and percutaneous implant.

Abstract: In vitro nucleation of apatite was studied over surface-modified Ti coatings prepared by reactive plasma spraying (RPS). An in-situ surface-modification of Ti particles is conducted by making use of plasma-enhanced reactions between the Ti particles and the reactive gaseous species in the plasma flame during plasma spraying. Surface-modified Ti coatings were deposited on Ti substrates by radio-frequency (rf)-RPS using a thermal plasma of Ar gas containing 1-6% N2 and/or 1-6% O2 at an input power of 16 kW. As a means of surface modification, Ti powders impregnated with 0.05-0.2 mol% Ca were also sprayed. Compositional changes in the coatings' surface after soaking in simulated body fluid (SBF) were examined by Fourier transform infrared spectroscopy (FT-IR) and thin film X-ray diffraction (TF-XRD). The Ti coatings prepared with Ar-O2 and Ar-N2-O2 plasma formed apatite after 3 days of soaking in SBF. On the other hand, no compositional change was observed in the surface of the Ti coatings sprayed with Ar-N2 plasma, even after 7 days of soaking in SBF. In SBF tests, we observed a retardation of apatite deposition for the Ca-added Ti coatings prepared with Ar-O2 and Ar-N2-O2 plasmas. Analyses by X-ray photoelectron spectroscopy indicated that the Ca impregnated in the RPS-Ti coatings formed a Ca-O compound.

Abstract: Ti-6Al-4V polished disks were immersed in a-calf-serum-solution and studied for resulting surface changes. The as-polished samples had more Ti2O3 close to the surface than titanium oxidizing in air – a result of low oxygen supply during polishing. Close to the interface with the metal, the TiO oxide is dominant. Immersion in serum caused the oxide thickness to become thicker, and to contain a higher concentration of the TiO2 component.

Abstract: Porous bioactive titanium implant was produced by plasma-spray method and succeeding chemical and thermal treatment. This porous titanium implant possess a porosity of 40% and complex interconnective porous structure. Mechanical property of porous titanium was characterized for compressive and 4-point bending properties, as well as compressive fatigue. Bone tissue response and biocompatibility of porous bioactive titanium implant was evaluated by in vivo osteoconductive model. Ultimate compression strength and bending strength were 280 and 101 MPa. Bone ingrowth showed significant increases in treated implant, while in these untreated porous titanium implant, bone ingrowth seemed to decrease with time. These results suggest that porous bioactive titanium is a candidate for clinical applications under load-bearing conditions.

Abstract: A layer of thick oxide film was formed on Ti6Al4V substrate by anodization. Subsequently alkali and heat treatment induced to form bonelike apatite layer on its surface in SBF for 7 days. The performances of the implants in vivo were observed by naked eyes and H.E. staining technique. The bone tissues around the surface and interface of the specimen in treated Ti6Al4V group were formed more quickly than those in Ti6Al4V and 316L alloy groups. H.E staining results of treated Ti6Al4V group showed the development of newly formed bone tissues on the implant-bone interface area.

Abstract: Electrophoretic deposition (EPD) was applied to forming apatite pattern. A pattern of holes was formed on a polytetrafluoroethylene (PTFE) board and a porous PTFE film was superposed on the PTFE board. Wollastonite particles were deposited on the PTFE film by EPD and wollastonite pattern was obtained. Then apatite was induced at the wollastonite deposited region by soaking in a simulated body fluid.

Abstract: Calcium phosphate bioceramics with an interconnective pore structure were produced by foaming of hydroxyapatite and methyl phenyl poly(silsequioxane) melts in the temperature range between 250 °C and 310 °C. The cellular structure of the resulting porous bodies were controlled by foaming parameters and filler load. A porosity of up to 92 % was achieved by decreasing the HAfiller amount and increasing the foaming temperature. Subsequent pyrolysis in air at temperatures of 900 °C and 1100 °C resulted in macroporous foams composed of HA and HA/b-TCP, respectively. The porous bodies with tailorable structure and composition are of interest for bone tissue engineering scaffolds and orthopedic implants.

Abstract: Biphasic ceramic consisting of tricalcium phosphate with α- and β -phases (αβ-TCP) is a candidate as biodegradable bone substitutes since its biodegradability may be controlled by the ratio of the phases. In the present study, preparation of porous αβ-TCP body with continuous pores of 10-50 µm in diameter was attempted using additives of Mg, and its in vivo behavior was examined. Powder of β-TCP was mixed with Mg and potato starch to form slurry, followed by loading in polyurethane foam. The sample was fired at 1400°C for 12 hours for sintering process. α-TCP content of the sample decreased with increasing the Mg content, while β-TCP increased. Ceramic body consisting of β-TCP phase was obtained when 1.0 mass% of Mg was added. Porosity of the body decreased with increasing the content of Mg. The αβ-TCP body with 80% porosity was obtained when the content of Mg was 0.1 mass%. The in vivo experiments showed that the rate of degradation of the obtained αβ-TCP was almost same as α-TCP, and much higher than β-TCP.