Key Engineering Materials Vols. 309-311

Abstract: Preparation of bioactive glasses was attempted utilizing waste bovine as raw resource. Bioactive and biodegradable batch compositions in the Na2O-CaO-SiO2 system were included with calcined bovine, whose phase was high-purity oxy-hydroxyapatite. Bovine inclusion as large as 40 mass% was shown to present highly bioactive glasses; bovine in the bioactive and biodegradable compositions presented glasses with controlled bioactivity and biodegradability, respectively. These indicate not only a plenty biological resource of bio-interactive materials, but also an alternative strategy for bioactive glasses with multi-functional applications.

Abstract: We investigated the electrical polarizability of MgO and B2O3 containing bioactive glass (MBG). The MBG material with good manufacturing properties but low bioactivity was electrically polarized at a high dc field. The electrical polarizability of MBG was evaluated by thermally stimulated depolarization current (TSDC) measurements and immersion in simulated body fluid (SBF). The early precipitation of calcium phosphate on the negatively charged surface of the treated MBG demonstrated the increased bioactivity of the material and confirmed its polarizability. It is suggested that the electrical interactions between the polarized MBG and ions in SBF promoted the formation of the calcium phosphate precipitation. Accordingly, the increased bioactivity of the MBG in SBF is suggested to demonstrate the conversion of MBG into electrovector ceramics by the polarization treatment.

Abstract: Na2O-CaO-P2O5-SiO2-Al2O3 (NCPSA) glass was investigated in its electrical polarizability by complex impedance and thermally stimulated depolarization current (TSDC) measurements. Moreover, the NCPSA glass was also subjected to a chemical treatment for bioactivity improvement. The effects of the electrical polarization and the chemical treatment on apatite formability of NCPSA glass were investigated by immersion test using simulated body fluid. From the result of complex impedance measurements, the activation energies for electrical conductivities NCPSA glass was 1.1eV. From the TSDC measurements, the polarized NCPSA glass showed monotonically increasing curves in depolarization current density spectra. The stored electrical charge calculated from TSDC measurements of the NCPSA glass polarized with electrical dc field of 2kV･cm-1 at 600°C for 1h was 4.91 mC･cm-2. The NCPSA glass treated with 1M NaOH indicated apatite formability in SBF and exhibited bioactivity. We disclosed that the combination of electropolarization and chemical treatment changed the apatite formability of the NCPSA glass in SBF, consequently, improved the bioactivity of the glass.

Abstract: Tricalcium phosphate (3CaO⋅P2O5, TCP) is known as a biodegradable material and already used clinically as important bone-repairing materials. However, the control of its bone-bonding ability, i.e. bioactivity, and biodegradability is not easy. On the other hand, diopside (CaO⋅MgO⋅2SiO2) ceramic shows a potential of direct contact with bone and high mechanical strength, but low biodegradability. We expected that a glass-ceramic containing TCP and diopside show high bioactivity and high mechanical strength, as well as biodegradability. Glasses with composition x(3CaO⋅P2O5)⋅(100-x) (CaO⋅MgO⋅2SiO2) (x = 0, 38, 50, 60 mass%) were prepared. They were pulverized and the compacts of the resultant powders were heated to obtain the glass-ceramics. Only diopside was precipitated at x = 0 in the glass composition, whitlockite (β-TCP) and diopside were at x = 38, 50 and 60, when the compacts were sintered at 1200 °C. The prepared glass-ceramics formed apatite on their surfaces in a simulated body fluid (SBF). This indicates that these glass-ceramics have a potential to show bioactivity.

Abstract: Antibacterial effects of three powdered bioactive glasses were compared by measuring the pH of the simulated body fluid in immediate contact with the glass powder particles and by cultivating four microorganisms in the powder-solution mixtures. After individual cultivation with the microorganisms the bioactive glasses showed ability to kill bacteria, but the effects were very dependent on glass composition and on the microorganism as well as on cultivation time. The results indicated that antimicrobial property of bioactive glasses correlates with their ability to change the pH of the body fluid in immediate contact with the glass. However, the increase in pH is not the only factor influencing the antimicrobial properties.

Abstract: Four different bioreactive ceramics were prepared using a sol-gel method and a standard melting process. The aim was to study antibacterial effect of these materials on the growth of Staphylococcus epidermidis. The dissolution (Si and Ca ions) of fine (≤ 45 !m) ceramic powders in a tryptone soya broth (TSB) was investigated. Also the pH changes in TSB solution were measured. In addition the adherence of Enterococcus faecalis (Ef) to materials was investigated. The bacterial adhesion was studied using scanning electron microscopy (SEM). In the bacterial and the adhesion test, CaPSiO2 and S53P4 had the strongest antimicrobial effect against studied bacteria. It was shown that bioreactive sol-gel derived ceramic with sufficient high Ca ion release (> 270 ppm) can reach strong antibacterial effect also at lower pH values (< 9.6).

Abstract: Composites of bovine bone derived HA with 5 wt% and 10 wt% of TiO2 were sintered at different temperatures. Their characterization comprised measurements of density, microhardness, and compression strength together with SEM observations and X-ray diffraction analysis. Better densification behaviour was achieved at higher sintering temperatures. The highest microhardness value was measured in the samples sintered at 1300°C. The best compressive strengths of the samples containing 5% and 10% TiO2 were obtained after sintering at 1300°C and 1200°C, respectively.

Abstract: The aim of this study was to prepare high performance biomaterials suitable for use at load bearing applications with high bioactivity. The hydroxyapatite (HA) was prepared from bovine bones via calcination technique. The bovine derived HA (BHA) was mixed with 5 and 10 wt% metallic titanium (Ti) and the obtained homogenous mixtures were pressed to produce the test samples. The compacts were sintered at temperatures between 1000 and 1300°C. Compression strength, density, and microhardness were measured. SEM and X-ray diffraction studies were also made. The best mechanical properties were obtained between after sintering at 1200-1300°C.

Abstract: Commercially pure titanium thin films were uniformly formed on inner surfaces of tissue culture dishes by DC sputtering method. Then, the thickness of the film was about 30nm and the films were thin titanium oxide layer on commercially pure titanium. MC3T3-E1 cells were normally cultured on the dishes. Then, The films on the dishes were not broken and did not decompose. After 24 hours, observations of the sample from the direction of the cells' bottom surfaces adhered the titanium oxide on the commercially pure titanium film by an inverted optical microscope succeeded. Therefore, the new technique is useful for observations the interactions between titanium oxide and cells.

Abstract: Plasma immersion process was investigated as a method for producing bioceramics coatings on metallic implants due to its advantages, which include the production of coatings on three-dimensional workpieces, with high density and superior adhesion. In this process, the oxygen plasma was utilized to form titanium oxide on titanium substrate. The structure, composition and surface morphology were studied using scanning electron microscopy (SEM) and X-ray diffraction. In addition a preliminary study has also been carried out, on TiO2-coated and uncoated titanium substrates, to analyse the in vitro biocompatibility (cytotoxicity evaluation and cell morphology).