Key Engineering Materials Vols. 342-343

Abstract: Zirconia was introduced into the dentistry as a metal-replacement material because of its outstanding mechanical properties like high flexural strength and fracture toughness. The purpose of this study was to evaluate bone response and examine the surface characteristics of zirconiabased implant. Screw shaped c.p. titanium implants(group 1), HA-based composite implants(group 2), HA/FA coated ZrO2 implants(group 3) and FA coated ZrO2 implants(group 4) were installed in rabbit tibias. After 4 and 12 weeks of healing period, the histomorphometric analysis was performed with an Olympus BX microscope connected to a computer. The percentage of bone-to-implant contact in the 3 best consecutive threads and the percentage of bone inside the same threads were calculated. the present study demonstrated the excellent bone response of ZrO2-based implants fabricated by various methods to combine the advantages of ZrO2, HA, and FA.

Abstract: We have fabricated the iron oxide nanowires directly from iron foils through the simple heating in N2 ambient. We have characterized the samples by means of scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray (EDX) spectroscopy, and selected area diffraction pattern. The EDX spectrum revealed that the nanowires contained elements of Fe and O. The iron oxide nanowires were crystalline with diameters in the range of 30-200 nm. We have discussed the possible growth mechanisms.

Abstract: Magnesium and its alloys are possible to develop new type of biodegradable medical magnesium alloys by using their active corrosion potential. The bio-corrosion properties of the high pure magnesium in the Hank’s solution were investigated in this paper, the results showed that high pure magnesium had a low corrosion rate and hydrogen release in Hank’s solution, when the pH value of solution was controlled at 7.5, the corrosion rate was under 0.2mm/year, the production of hydrogen was about 0.15ml/cm2, and if the solution wasn’t controlled on pH value, the corrosion rate was about 0.02 mm/year, production of hydrogen was about 0.1ml/cm2 . Result of in vitro Kinetic clotting time test and animal implant prep-test showed that High pure magnesium had good thromboresistant property and tissue compatibility, pure magnesium can biodegrade lowly in animal body and formed surface apatite, which proportion of Ca/P was similar with bone tissue.

Abstract: The in vitro blood compatibility of a new nickel free high nitrogen austenitic stainless steel Fe-Cr-Mn-Mo-N (BIOSSN4) was studied by the kinetic clotting time test and the platelet rich plasma adhesion test in this paper. In comparison with 316L stainless steel, the kinetic clotting time of BIOSSN4 steel are longer, and only causes less activation of platelets in platelet adhesion test, which was indicated by their morphology and low spreading. The experimental results reveals that the BIOSSN4 stainless steel has better blood compatibility, the blood compatibility mechanism of steels was analyzed based on surface tension and interfacial tension between the steels and blood.

Abstract: The present study was designed to test the hypothesis that oxidative stress mediates chromium-induced cytotoxicity in MG63 cells and antioxidant N-acetyl-cysteine (NAC) can provide protection for osteoblasts against chromium-induced oxidative stress. We assessed the effects of chromium ions on cell viability, the level of intracellular reactive oxygen species (ROS) and intracellular ultrastructure in the presence or absence of NAC. A time- and concentrationdependent increased cytotoxicity, intracellular ROS generation was found and intracellular ultrastructure was damaged when cells were exposed to Cr+6. NAC afforded dose-dependent reduction to the cytotoxicity and level of cellular oxidative stress induced by Cr+6. Intracellular ultrastructural alterations were reduced by the NAC pretreatment, too. Cr+3 had no significantly negative influence in MG63 (5-20μM). Our results suggest that oxidative stress might be involved in Cr+6 induced cytotoxicity in osteoblasts. NAC can play a critical role against Cr+6- induced cytotoxicity. Cr+3 (5 -20μM) had no significant cytotoxicity in MG63 cells and cellular oxidative stress was not found, too.

Abstract: The aim of this study is to fabricate an implant framework for tissue engineering by sintering titanium beads and coating with hydroxyapatite and test its biocompatibility and bioactivity in vitro. The porous titanium with and without hydroxyapatite coating were involved in study groups. Osteoblastic proliferation, activity of alkaline phosphatase, mRNA of osteocalcin and bone sialoprotein were detected by MTT-assay, ALP test and real-time polymerase chain reaction respectively. The results indicated that the porous titanium material with/without HA coating could promote osteoblastic proliferation significantly contrast to the control group. However, only porous titanium with HA coating increased alkaline phosphatase, osteocalcin and bone sialoprotein gene expression apparently and had statistically differences with the other two groups. Abstract no. is TE-Po-044

Abstract: The aim of this study is to optimize the economic net-shape forming of titanium and titanium alloys for the biomedical application. The alpha-case formation reaction between titanium, and Al2O3, ZrO2, CaO stabilized ZrO2 and ZrSiO4 mold were examined in a plasma arc melting furnace. Regardless of the thermodynamic approach, α-case formation reactions still remain to be eliminated with the complex chemical milling processes. The reason why the α-case generated cannot be explained by the conventional α-case formation mechanism. However, from the experimental results and thermodynamic consideration, it can be confirmed that the α-case is formed not only by interstitial oxygen atoms but also by substitutional metal atoms dissolved from mold materials. Based on the interstitial and substitutional α-case formation mechanism, α-case controlled net-shape forming of titanium and titanium alloys can be possible for the biomedical application.

Abstract: We investigated the relationship between kinematic and kinetic characteristics of foot joints resisting ground reaction force (GRF). Passive elastic characteristics of joint were obtained from the experiment using three cameras and one force plate. The relationship between joint angle and moment was mathematically modeled by using least square method. The calculated ranges of motion were 7o for TM joint, 4o for TT joint and 20o for MP joint. With the model that relates joint angle and plantar pressure, we could get the kinematic data of the joints which are not available from conventional motion analysis. The model can be used not only for biomechanical analysis which simulates gait but also for the clinical evaluations.

Abstract: Indium oxide (In2O3) films were successfully grown on LiAlO2 substrates using the triethylindium (TEI) as a precursor in the presence of oxygen in the metalorganic chemical vapor deposition process. We have established the correlation between the substrate temperature and the structural properties. The grain structures were clearly shown on the surface of the films deposited at 350°C. The root mean square (RMS) surface roughness of the In2O3 films increased with increasing the substrate temperature. A photoluminescence measurement at room temperature exhibited a yellow-green emission band centered at 585 nm.

Abstract: The fixation of the vertebral column using transpedicular screws is a well-establish technique. Multi-axial pedicle screw designs allow deviation of the screw away from the perpendicular to the longitudinal rod, which facilitates application of a screw-rod system such as PRIMA OCT into the curved spine. This study was performed a static (compression bending and torsion) and dynamic (compression bending fatigue) empirical analysis of PRIMA OCT component such as pedicle screw, rod and set screw based on the guideline of ASTM F136-98 using Ultra-high Molecular Weight Polyethylene (UHMWPE) blocks as test vertebral bodies.