Papers by Keyword: Hydroxylapatite

Abstract: Polystyrene (PS) microspheres were prepared by dispersion polymerization method and using PS microspheres as pore former porous hydroxylapatite (HA) was prepared by Liquid phase precipitation method. The phase constituent was analyzed by X-ray diffraction(XRD) and by Fourier transform infrared(FTIR) and the microstructure was observed under scanning electron microscopy (SEM), field emission scanning electron microscope (FE-SEM) and transmission electron microscopy (TEM). The results showed that the prepared porous HA was of high purity and their pores were evenly distributed, with pore about 200nm in diameter. PS microspheres were probably the most economic and environmental pore-forming materials.

Abstract: Mesoporous hydroxylapatite was prepared by Liquid phase precipitation method, using Polystyrene microspheres as template. Polystyrene microspheres mixed uniformly with the prepared hydroxylapatite slurry, then the mixture dryed and sintered at reasonable temperature, mesoporous hydroxylpatite ceramics were obtained. The phase constituent was analyzed by X-ray diffraction (XRD) and the microstructure was observed under scanning electron microscopy (SEM). The results showed that the prepared mesoporous hydroxylapatite ceramics were of high purity and their pores were evenly distributed, with big pore 0.8-1.0 um and small pore 30-80nm in diameter.

Abstract: Hydroxylapatite, titania and Bioglass 45S5 are the components generally used for the production of bioactive biomaterials for years. In literature, although the binary composites with the permutation of three components exist, a ternary composite has not yet been tried. Primarily, Bioglass 45S5 was cast, its thermal analysis (Differential thermal analysis (DTA), dilatometric analysis), phase analysis (X-Ray Diffraction (XRD) ), microstructural characterization (Scanning Electron Microscopy (SEM) ) were performed. Then Bioglass 45S5 powder was ground to fine powder to make its particle size closer to the hydroxylapatite and the titania powders. The particle size of the powders were determined using the laser particle sizer. The DTAs of the 3 components, separately and mixed, were performed. They were then mixed, and ball-milled during 24 hours for a better homogenization. Following drying for 24 hours, pellets of 1 inch diameter were obtained using unaxial manuel press and sintered at 1000, 1100, 1200 °C. Mechanical testing (compression and microhardness), porosity measurement (The Archimèdes Method), phase determination (XRD) and microstructural characterization (SEM) of the composites were then performed. As a conclusion, when sintering temperature was increased, the porosity in the structure was decreased. Between 1100 °C and 1200 °C, a phase transformation occurred. The results of microhardness ( 24.6, 38.99, 316.2 HV (500gf for 15 sec) for the composites sintered at 1000, 1100, 1200 °C, respectively) and subsequent compression tests (93.023±10.5, 298.14±78.074, 371.9684±38.36 MPa, respectively) approved the possible phase transformation between 1100 °C and 1200 °C along with the XRD results.

Abstract: Minocycline, a semi-synthetic tetracycline antibiotic, was incorporated into gelatin- hydroxyapatite (HA) composite by using a biomimetic co-precipitation method, Firstly, a certain amount of acidic solution of hydroxyapatite was added into gelatin solution dropwise. After that, different amounts of minocycline (0mg, 50mg, 100mg, 200mg, 300mg) solution was added into the reaction system respectively , and obtain the hydroxyapatite - gelatin- minocycline composite. The results showed that the amount of the minocycline impacted the structure of the composite, and minocycline affects HA crystal growth by maybe bonding to 300 face. The approach described here may provide a basis for the preparation of an antibacterial biomaterial for bone regeneration.

Abstract: A β-NaCaPO4 containing borate glass ceramic is prepared. Two kinds of porous scaffolds are constructed by sintering glass particles in the size of 300~400μm and binding glass particles in the size of 200~300μm using 5 wt% sodium silicate solution respectively. The reaction of the scaffolds in the SBF solution, the bioactivity and biodegradation of the scaffolds are characterized by weight loss analysis, XRD, and SEM. The same is done to the 45S5 scaffolds as comparison. The results show that the borate glass ceramic scaffolds have better biodegradation and bioactivity. The final weight loss of the sintering scaffolds and the binding scaffolds are 50.71% and 70.68% respectively, which indicates that the high temperature during the course of the sintering has great influence on the bioactivity of the borate glass ceramic scaffolds. The XRD indicates that the hydroxylapatite has formed on the both kinds of the scaffolds, and the hydroxylapatite on the binding scaffolds has higher degree of crystallinity. The residual glass phase of the glass ceramics contributes to a quick apatite formation on the scaffolds due to its high solubility in SBF solution, while the β-NaCaPO4 crystal phase leads to a slower apatite formation which guarantees an improved mechanical stability of the scaffold. This combined reaction mechanism enables the biodegradation rate of the scaffolds to match with the growth rate of tissues, which makes the scaffolds a good potential prospect in the field of tissue engineering.

Abstract: Hydroxylapatite(HAP) nano-whiskers are prepared by reaction-precipitation in the submerged circulative impinging stream reactor(SCISR), with (NH4)2HPO4 and Ca(NO3)2 as the reagents; and the products are characterized by X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). The results TEM measured indicate that the product prepared under typical operation conditions is average-sized 15nm and 50-70nm long. Multiply repeated experiments illustrates that, because of the excellent performance of the reactor, the preparation process can be easily controlled to yield nano rod/whisker hydroxylapatite with very narrow size distribution.

Abstract: It has been proven that HA coatings on implant materials treated with silver exhibited excellent antibacterial effects. Silver (Ag) ions were successfully incorporated into HA structure with the precipitation method. Although this method was pretty much suitable for the synthesis in powder form, it is not applicable to in-situ coating processes. The aim of the current study is to synthesize Ag ion incorporating HA via the decomposition of EDTA Chelate. For this reason, Ag doped crystalline-sodium and carbonate-containing HA solutions will be prepared using calcium-EDTA in a sodium phosphate solution, hydrogen peroxide and silver nitrate. As the source of Ag ions, silver nitrate was added into the solution in the desired proportions. Then, the samples were sintered at temperatures from 800oC to 1100oC and characterized with XRD and SEM.

Abstract: Dental enamel is the most highly mineralised and hardest biological tissue in human body [1]. Dental enamel is made of hydroxylapatite (HAP) - Ca5(PO4)3(OH), which is hexagonal (6/m). The lattice parameters are a = b = 0.9418 nm und c = 0.6875 nm [1]. Although HAP is a very hard mineral, it can be dissolved easily in a process which is known as enamel demineralization by lactic acid produced by bacteria. Also the direct consumption of acid (e.g. citric, lactic or phosphoric acid in soft drinks) can harm the dental enamel in a similar way. These processes can damage the dental enamel. It will be dissolved completely and a cavity occurs. The cavity must then be cleaned and filled. It exists a lot of dental fillings, like gold, amalgam, ceramics or polymeric materials. After filling other dangers can occur: The mechanical properties of the materials used to fill cavities can differ strongly from the ones of the dental enamel itself. In the worst case, the filling of a tooth can damage the enamel of the opposite tooth by chewing if the interaction of enamel and filling is not equivalent, so that the harder fillings can abrade the softer enamel of the healthy tooth at the opposite side. This could be avoided if the anisotropic mechanical properties of dental enamel would be known in detail, hence then another filling could be searched or fabricated as an equivalent opponent for the dental enamel with equal properties. To find such a material, one has to characterise the properties of dental enamel first in detail for the different types of teeth (incisor, canine, premolar and molar). This is here exemplary done for a human incisor tooth by texture analysis with the program MAUD from 2D synchrotron transmission images [2,3,4].

Abstract: Not many studies have been found in the literature on the effect of Ag ions on the structure and phase stability of hydroxylapatite which may be recognized as important information in the scaffold fabrication. The objective of the current study is to develop a better understanding on the structure and behavior of the antibacterial Ag incorporated hydroxylapatite. In order to do this, Ag doped hydroxylapatite was made by a precipitation method, and sintered in air at 1300oC. The materials were characterized by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), density measurements and scanning electron microscopy (SEM).

Abstract: Two methods of loading bisphosphonate (BP) into hydroxylapatite (HA) coatings on crystalline TiO2 surfaces were investigated to improve bone ingrowth to implant surfaces. In the study the BP pamidronate was used. Ti-plates coated with crystalline TiO2 were soaked in phosphate buffer saline (PBS) for 7 days at 40° C and thereafter soaked in solutions of BP, 0.5 mg/ml for 15 or 60 minutes (fast loading method). In the second method BP was dissolved into PBS in different concentrations before immersion of the discs for 7 days (co-precipitation method). Surface and bulk were analysed using electron spectroscopy for chemical analysis, scanning electron microscope and x-ray diffraction. Release of BP was studied using alternating ionic current method. It was shown that fast loading by soaking in a BP solution for 15 minutes was sufficient to load BP into a HA coating. Co-precipitation showed that a thin layer of calcium phosphate crystals containing BP can be deposited directly onto a crystalline TiO2 surface.