Key Engineering Materials Vols. 330-332

Abstract: The microstructure of a Fragum unedo shell is observed with a scanning electronic microscope (SEM). It shows that the shell is a kind of bio-ceramic composite consisting of aragonite and collagen protein layers. The observation also shows that the aragonite layers consist of thin and long aragonite sheets. A kind of particular herringbone structure of the aragonite sheets is found. In the structure, the aragonite sheets in an arbitrary aragonite layer make a crossed angle against that in its neighboring aragonite layers. Based on the SEM observation the comparative experiments in the maximum pull-out forces of both the herringbone and conventional 0°-structures are conducted. It shows that the maximum pull-out force of the herringbone structure is markedly larger than that of the 0°-structure, and the larger the crossed angle is, the more the maximum pull-out force of the herringbone structure will increase compared with that of the 0°-structure.

Abstract: Novel poly(ε-caprolactone)-organosiloxane hybrid containing amine group was synthesized through sol-gel method. Triethoxysilane end-capped poly(ε-caprolactone) was prepared by reaction with α,ω-hydroxyl poly(ε-caprolactone) and 3-isocyanatopropyl triethoxysilane. It was then hydrolyzed and co-condensed with aminopropyl triethoxysilane through sol-gel method. The success of hybridization was evaluated by FT-IR by new formation of siloxane group. Osteoblast-like cell responses were assessed on this new hybrid material for the potential application as a bone tissue engineering scaffold. The cell responses were compatible with those on pure poly(ε-caprolactone) used as a control.

Abstract: This study examined the role of tissue adhesives during early healing and the effects of tooth ash and plaster of Paris on bone healing in the presence of osteoporosis. Sixty rats were assigned to five groups randomly and each group was further divided into two subgroups, which were examined 4 and 8 weeks after implantation. Histologic sections and histomorphometric analysis of defects were obtained 4 and 8 weeks after surgery. Bone formation was significantly better in the non-ovariectomized groups compared to the ovariectomized group. A mixture of tooth ash and plaster of Paris is recommended, but not tissue adhesives, in ovariectomized cases.

Abstract: The corrosion behavior of titanium in hydrogen peroxide solutions was studied by measuring the titanium ions concentration using spectrophotometer. The influence of additives (K+ ， Ca2+ ，Na+ ，Mg2+ ，Cl- ，HPO4 2-, H2PO4 - ) on the corrosion behavior of titanium was examined. The results indicated that Ca2+ exhibited the highest inhibition to the titanium corrosion in hydrogen peroxide solutions, while HPO4 2- behaved as an accelerator to the corrosion. It was suggested that the Ca2+ was absorbed on the titanium surface to form a thin film of CaTiO3 or CaO2, and consequently, inhibited the corrosion of titanium. The acceleration of the titanium corrosion in the present of HPO4 2- was caused probably by the increased defect of surface oxide films after absorption of HPO4 2- ions.

Abstract: A series of dialdehyde cellulose samples with varied aldehyde content were prepared by oxidation of bacterial cellulose with sodium periodate. The X-ray diffractometry profile showed that the crystallinity degree of bacterial cellulose was 66%, but that of the dialdehyde cellulose (containing 12% aldehyde ) was 56%. Thermal decomposition of these dialdehyde cellulose samples and bacterial cellulose were studied by thermogravimetry. The decomposition of bacterial cellulose in nitrogen started at 230 and rapid weight loss occurred between 300-400. The introduction of dialdehyde group to bacterial cellulose resulted in significant shifts of decomposition to lower temperature range. The decomposition of dialdehyde cellulose (12% aldehyde ) started at 180 and rapid weight loss between 200-350. The temperature of rapidest weight loss shifted from 340 of bacterial cellulose to 290 of the dialdehyde cellulose(12% aldehyde).

Abstract: Rapid Prototyping (RP) technique was used to prepare porous Ti6Al4V with designed structures. Firstly, a 3-D interconnected porous wax mold with uniform pore size and porosity was designed by computer aided design (CAD), and fabricated by 3-D printing machine, then an aqueous Ti6Al4V slurry prepared from Ti6Al4V powder and binders was cast in these molds. The green bodies were subjected to drying, debinding and finally sintering at a high temperature and a high vacuum to obtain porous Ti6Al4V. Optical microscopical observation, scanning electronic microscopical observation, mechanical test were performed on the obtained porous Ti6Al4V with regard to the porous structures and mechanical properties. The porous Ti6Al4V made by RP technique posses designed structure with uniform pore size, porosity and interconnection. With the computer aided design, it is easy to improve the mold structure with predicted or controlled macrostructure and microstructure according to the custom requirement.

Abstract: Poly(vinyl alcohol) (PVA) hydrogel is a promising articular cartilage biomaterial. In this paper, the effects of different variable factors on the friction coefficient of Poly(vinyl alcohol) (PVA) hydrogel were investigated when sliding against stainless steel ball by ball-pan tribometer. Factors included lubrication condition, sliding speed, diameter of stainless steel ball, and load. It was shown that the free water in PVA hydrogel has an excellent lubrication on the counterparts. The friction coefficients have little difference between dry and lubricants lubrication condition at initial friction test. With the friction test time prolonged, friction coefficient of PVA hydrogel under dry condition increased rapidly. Friction coefficient decreased with the increase of sliding speed and the diameter of stainless steel ball, and increased with the increasing load. The rising rate of friction coefficient at low load region is obviously larger than that at high load region.

Abstract: In the present study, Functionally gradient HA-ZrO2-Ti coatings (FGC) on Ti6Al4V were prepared by the plasma spraying process. The residual stress and surfacial morphology of coating were studied by X-ray diffraction and scanning electron microscopy with an energy dispersive spectroscopy. The results showed that: (1) the residual stress of FGC is 72.1Mpa, much lower than that of single HA coating, (2) The surfacial morphology of the FGC showed typical characteristics of plasma-sprayed coating, no microcracks was observed because of its the thermal expansion matched between the gradient coating and substrate.

Abstract: A novel poly(lactic acid) (PLA)/calcium carbonates hybrid membrane containing siloxane was prepared using aminopropyltriethoxysilane (APTES) for biodegradable bone guided regeneration. The PLLA in the membrane was an amorphous phase. By heating the membrane at 100 °C for 1 h, the PLLA in the membrane crystallized. Numerous pores of 0.5-1 ,m in diameter were newly formed at the surface. After soaking the membranes before and after heat-treatment in simulated body fluid, the amount of silicon species in SBF released from the membrane after heat-treatment was higher than that before heat-treatment. A test of osteoblast-like cellular proliferation on the membrane showed the membrane after heat-treatment has much higher cell-proliferation ability than that before heat-treatment.

Abstract: This studied determined the clinical effect of antibiotic use at the site of bone defect restoration in patients with osteoporosis, using tooth ash and plaster of Paris in ovariectomized rats. Forty-eight rats were assigned to four groups randomly and each group was further divided into 4 and 8 weeks after implantation. Histologic sections of the defects were obtained after surgery for histomorphometric analysis. Comparing each week, a significant difference was seen in bone formation by 4 weeks. Compared to controls, new bone formation increased significantly with tooth ash and saline, tooth ash and gentamicin, and tooth ash and gentamicin after ovariectomy. Tooth ash and saline resulted in the best bone formation. The degree of new bone formation was slightly lower when tooth ash and gentamicin were used compared to when tooth ash and saline were used. When tooth ash and gentamicin were compared according to ovariectomy, bone formation was significantly inhibited by ovariectomy at 4 weeks, while no significant difference was seen at 8 weeks.