Abstract: Present study evaluated the feasibility of apatite monolith preparation from calcium
sulfate monolith using ammonium phosphate solution. We found that calcium phosphate monolith transforms to apatitic monolith without changing its original morphology when a proper temperature and a proper phosphate solution was selected. Prepared apatite was B-type carbonate apatite with low crystallinity. Although mechanical strength of the apatite monolith was lower than original calcium sulphate monolith, we concluded present method may be useful for the fabrication
of apatite monolith since we can prepare different shape of apatite monoliths based on the setting reaction of calcium sulphate and compositional transformation to apatitic mineral.
Abstract: Bioactive glass-ceramics of the SiO2-CaO-P2O5-MgO system were fabricated by
sol-gel-self propagating method. Two Gel-derived materials discs， 5S and 3S， were prepared by compression of powders. The materials obtained were examined in vitro with regard to the dissolution behavior and the formation ability of calcium phosphate layer on the surfaces of samples in simulated body fluid (SBF). Concentration of ions and pH value in SBF were determined by ICP-AES and micro acidity meter after 3S and 5S were immerged in SBF for intervals from 6h to 15 days and the surface characteristic of 3S and 5S soaked were determined by SEM. Experiment results showed that the formation ability of calcium phosphate on the surface of gel-derived materials depended on the speed of dissolution of samples, which related to original chemical composition and size of crystal on the surface of materials. With decreasing of Si content and increasing of Ca content, smaller crystal could be formed on the surface of 3S, which tended to dissolve more quickly in SBF. Solubility product of calcium phosphate can be reached more easily in the solution with high concentration of Ca and P and bone-like carbonate apatite formed easily on the surface of 3S.
Abstract: The new-style injectable root canal filling material was prepared by hydroxyl apatite
(HA), calcium hydroxide (Ca (OH) 2), iodoform (CHI3) and silicon oil. The material was injected into the isolate teeth to observe the sealing effect through marinating the isolate teeth in SBF and 1% methylblue solution. The practical effect of this material through clinical trials ten patients including fourteen teeth was also evaluated. After six months follow-up, patients have no any uncomfortable. This root canal filling material has good injectability, good biocompatibility, and is very convenient to manipulate. The relevant results suggest that it has good prospect of clinical application.
Abstract: Mice macrophages which were mixed with β-tricalcium phosphate (β-TCP) ceramics powder were cultured, both calcium and phosphorus concentrations in the culture medium were evidently higher than that of β-TCP ceramics powder without cells. The microscope and SEM observation showed that macrophages wrapped β-TCP particles, and then phagocytized them into cytoplasm. The pH values inside and outside macrophage in β-TCP-bearing were tested. The histochemistry observation showed that there were many carbonic anhydrase positive grains in the
cytochylema of macroghage after β-TCP ceramics powder being implanted. TEM investigation indicated that many β-TCP particles were phagocytized into the cytochylema of macroghage, and then vacuole was found after particles had degraded. The results showed that macrophages could take part in the degradation of calcium phosphate ceramics in two different ways.
Abstract: Porous calcium polyphosphate(CPP) have been shown to promise for tissue engineered implant application. The process from Ca(H2PO4)2 to CPP, as a polycondensation reaction, has been researched to evaluate the number average degree of polymerization. CPP with different degree of polymerization were prepared by controlling the calcining time. Amorphous and different crystalline CPP were prepared by the quenching from the melt and crystallization of amorphous CPP. Two
specimens were soaked into citric acid and tris-buffer solution for 1 to 30 days. The weight loss of CPP with different degree of polymerizations and crystal types are different. With the increasing of degree of polymerization, the weight loss during the degradation is decreasing, contrarily the strength of CPP is increasing. The degradation velocity of amorphous CPP, α-CPP,β-CPP and γ-CPP with the same degree of polymerization decreased in turn at the same period. The full weight loss period of CPP can be changed between 17 days and more than 1 year. The degradation and deposition was faster in the citric acid than the tris-buffer solution.
Abstract: A calcium phosphate bone substitute material was prepared and its rheological behavior and injectability were studied in this work. The effects of temperature, L/P ratio and adjuvant on the rheological properties and injectability of the pastes were discussed. The results show that the calcium phosphate bone substitute material is injectable with good fluidity and is suitable for the clinical applications. The rheological behavior and injectability of the bone substitute material can be improved by adding adjuvants and optimizing L/P ratio.
Abstract: Submicron hydroxyapatite powder with particle size in the range of 80-250 nm was
fabricated by sol-gel process in our laboratory. To make ceramic slurry with good flowability, the powder was mixed with binder and distilled water. The binder was consisted of acid magnesium and aluminum phosphates. The polyurethane foam was impregnated in the slurry, squeezed out the excess slurry and the composite porous body gained. Green body was dried in room temperature naturally and then moved to electric furnace and sintered at high temperature. The sintered scaffolds possess interconnected open pore structure and with a porosity of 70-85% and compressive strength 10-20 MPa, and was consisted of doped HA and other phosphates. The scaffolds were co-cultured with osteoblasts in vitro. SEM analyses revealed that the cells adhere to the ceramic surface, proliferate and growth properly. Experimental results showed that the scaffold possesses good biocompatibility and could be used in bone tissue engineering.
Abstract: Instent restenosis (ISR) has been a key factor that restricts the further use of
intraoronary stents. And the mechanical interaction between the stent and the artery has been indicated as one of the significant causes for the activation of stent-related restenosis. However, there is very little quantitative information about the interaction of stent with artery. In order to improve the general understanding of coronary stenting, finite element method (FEM) has been used to model the revascularization of a stenosed artery through the insertion of a balloon-expandable stent. Given a stent design, the deformed shape of the stent and possible areas
of the artery injury were presented. The fact that the distal end of stent penetrated into the artery wall may help to explain the phenomena that much restenosis occurs at the ends of stents. The recoil ratios of the stent model, the plaque-artery model and the stent-plaque-artery model were 2%, 26.7% and11.3%, respectively. They were well consistent with the experimental data. In conclusion, this work would be helpful for the general understanding of intraoronary stent implantation and stent design optimization.