Key Engineering Materials Vols. 288-289

Abstract: It is important to obtain mechanical coupling between dental implants and bone, because the lack of mechanical coupling may cause bone loss around implants. In this research, a new cylindrical dental implant composed of three parts was designed to offer favored mechanical environment for the bone. A special gap structure changed the means of the stress transmission and decreased the stress in the cortical bone around the neck of the implant. Through finite element analysis (FEA) of stress distribution in bone around implant-bone interface, the advantages of this new implant (reducing stress concentration in cervical cortex and satisfying varieties of clinical needs) were verified. The peak stress for the new design was about 30 percent less than that of the traditional implant and the flexibility of the design was also confirmed by changing the gap depth and the wall thickness.

Abstract: The objective of this study was to develop an efficient method for the production of bioactive bone morphogenetic protein 2 (BMP-2). A recombinant plasmid encoding mature human BMP-2 was transferred and expressed at a high level in E.coli. Most of the aimed proteins existed in inclusion bodies. The non-active recombinant human BMP-2 (rhBMP-2) monomer in inclusion bodies was refolded and simultaneously purified using hydroxyapatite (HA) chromatography. After oxidization of the monomer, the rhBMP-2 dimmer showed biological activity by the induction of alkaline phosphate activity in C2C12 cells. The refolding yield was about 30% and the purity was about 90% just by one chromatography process.

Abstract: The potential protective roles played by green tea compounds (GTPCs) against reactive oxygen species-induced oxidative stress in cultured fetal human dermal fibroblasts (fHDFs) were investigated according to cell viability measurement methods, such as fluorescence double staining followed by flow cytometry (FCM), MTT assay and crystal violet uptake. Oxidative stress was induced in the fHDFs, either by adding 50 mM H2O2 or by the action of 40 U/L xanthine oxidase (XO) in the presence of xanthine (250 µM). FCM analysis was the most suitable to show that both treatments produced a significant (p < 0.05) reduction in the fHDF viability, attributed to its high sensitivity. On the microscopic observations, the cell death with necrotic morphology was appreciably induced by both treatments. These oxidative stress-induced damages were significantly (p < 0.05) prevented by pre-incubating the fHDFs with 200 µg/ml GTPC for 1 h. These results suggest that GTPC can act as a biological antioxidant in a cell culture experimental model and prevent oxidative stress-induced cytotoxicity in cells.

Abstract: Periodic structures, such as photonic crystals and gratings, offer the ability to control light propagation and produce structural colors (not produced by pigments). Structural colors are quite widespread in nature, such as in opals and some animals. The abalone shells attract much attention due to its fracture resistant. In present work, we report on the microstructure of the surface area in where the iridescence color appears found in abalone shell shows a groove structure of blaze grating. The scanning electron microscopy (SEM) images of its iridescent layer show layers of platelets. The abalone shell has a statistically regular arranged tile structure. This specific tile structure serves as a two-dimensional grating to cause the iridescence phenomenon. Unlike opals, the iridescence color of the abalone shells is not directional due to the two-dimensional arrangement of the reflection grating structure and the convex shape of the tiles.

Abstract: Molluscan shell is a typical biocomposite in nature. It possesses excellent strength, stiffness and fracture toughness, which are closely related to its exquisite microstructure. SEM observation on clam’ shell shows that the shell is a kind of layered ceramic composite consisting of aragonite sheets and protein matrix. The aragonite sheets have long and thin shape and are arranged in a parallel manner. The higher fracture toughness of the shell is analyzed based on its representative model and the concept of maximal pullout energy. Analysis shows that the long and thin shape as well as the parallel arrangement of these sheets will substantially improve the maximal pullout energy of the sheets and the fracture toughness of the shell.

Abstract: This study fabricated polyurethane foam after transforming the cell structure from a convex polyhedral shape to a concave shape. Polyurethane was synthesized and fabricated after changing the cellular structure of the foam using two methods. Scanning electron microscopy showed that the cellular structure was a more concave structure than in control foam. The Poisson’s ratio of the experimental foam was negative. The average range of the Poisson’s ratio was –3.4~0, versus 0.3~1.3 for the control foam.