Papers by Keyword: HAp

Abstract: A study was conducted on gamma-ray modified nanoHydroxyapatite (HAp)/Ultra High Molecular Weight Polyethylene (UHMWPE) composite as orthopedic implant material. This study aims to characterize the effect of gamma radiation on the physical, chemical, and mechanical properties of UHMWPE/HAp composites so that they can be used as orthopedic implant materials. The composite film was irradiated with gamma rays at a dose variation of 0 kGy, 15 kGy, and 30 kGy and a dose rate of 8 kGy/hour. Composites before and after radiation were tested for physical, chemical and mechanical properties. Physical properties test includes surface microstructure analysis; chemical properties test includes phase and functional group analysis; mechanical properties test, including hardness, tensile strength, and elongation at break. The results obtained are gamma radiation from IRKA changes the chemical properties of composites in terms of crosslinking and the number of radicals, as well as mechanical properties in terms of hardness, tensile strength, and elongation at break with different changes from the initial state before radiation. The best mechanical properties were obtained at 25% HAp composition in a dose of 30 kGy with a hardness (shore A) of 97.17; tensile strength of 18.15 MPa; and elongation at break of 17.85%, so that the UHWMPE/HAp composite has potential as an orthopedic implant material following the Ultimate Tensile Strength (UTS) of cancellous bone ranging from 10-20 MPa.

Abstract: In cosmetic dentistry, bleaching and laminate veneer methods are common treatments to improve the appearance of teeth. However, there are limitations to these treatments, as they damage the enamel which are not capable of recovering naturally. In this study, novel hydroxyapatite (HAp) sheets, which enable both enamel restoration and aesthetic treatments, were developed. Results indicated that the lower range of the sintering temperatures, of the pulsed laser deposition targets, produced lighter shades of amorphous Calcium phosphate (ACP) sheets. Subsequently, the post-annealing process of the sheets induced crystallization processes of the ACP sheets, to form HAp sheets, and improved the shade rank of the sheet. The shade rank of the developed sheet (6.8 ± 0.2) was almost comparable to the average shade rank of the teeth of Japanese people, within a range of 6.5 to 7.0.

Abstract: This paper focuses on characterization of Hydroxyapatite coated SS316 L using Pulse vapour deposition method. The target material (Hydroxyapatite) has been synthesised chemically in laboratory through the addition of (NH₄)2HPO₄ with Ca (NO₃)₂4H₂O solution. This mixture has been converted in to circular blocks through various processes as explained below and coated over the stainless steel substrate. The morphological characteristics of the coating and surface roughness analysis have done through SEM and AFM. Also the hardness and corrosion resistance of the coating are examined. It has been found that improved hardness when compared with SS316L (175 Hv) to Hydroxyapatite (245 Hv) coated SS316 L. Also the results of corrosion resistance test after 250 Hrs of experiment found that formation of red rust is attained for uncoated samples where as Hydroxyapatite coated samples remains unchanged.

Abstract: The hierarchical hydroxyapatite (HAP), such as needle-shaped, spherical and flower-like, was successfully synthesized by a homogenous precipitation method with poly (styrene)-block-poly (acrylic acid) (PS-b-PAA)_. The self-assembled “crew-cut” micelles of amphiphilic block copolymer were found to play an important role in directing the nucleation and growth of HAP crystals. The morphology, crystal phrase and chemical structure of HAP crystal were investigated by scanning electron microscope (SEM), X-ray diffractions (XRD) and Fourier transform infrared spectroscopy (FT-IR) respectively.

Abstract: Microcracks and trabecular fractures can be observed in physiological bone. Biomimetic hydroxyapatite (HAp) scaffolds have been strongly needed in bone regenerative medicine. We have been developing the combination method of the partial dissolution-precipitation techniques involving the stirring-supersonic treatment in 1.7×10^-2 N HNO₃ solution containing Ca^2＋and PO₄^3- ions to improve the surface and the bulk of commercially available synthetic HAp block (82.5% in porosity, 50-300µm in macropore). The modified HAp was named as a partially dissolved and precipitated HAp (PDP-HAp). The aims of this study are to characterize the PDP-HAp and to observe cell response for the ceramics in rat scalp tissue. The PDP-HAp exhibited the macropore sizes of 50-200µm, the porosities of 85-90%, and the specific surface areas of 1.0-2.0 m²･g^-1, with many micro-cracks. Twenty rats were divided into 2 groups. At 9 months, bone induction occurred inside the many pores in the PDP-HAp group, while bone and cartilage were not found in the HAp group. We believe that osteoinduction by the PDP-HAp is different from the process of BMP-loaded HAp-induced bone formation. The PDP-HAp might be applied as potential ceramics with osteoinductive properity and excellent biocompatibility in difficult bone regenerative cases.

Abstract: The processing of porous ceramics spheres (PCS) has been developed for biphasic calcium phosphates (BCP), hydroxyapatite (HAp) and beta tricalcium phosphate (β-TCP) in order to be used mostly as bone fillers and drug delivery systems. The importance of the PCS is due to better accommodation of them in order to fill empty spaces and also because is more friendly to cells and bone tissue growth. Also is important to obtain a surface roughness to increase the surface area in contact with the living tissue and their fluids. There are several methods used to achieve the PCS form and most of them use suspensions based on liquids immiscibility effect or additives. The aim of this work was to achieve PCS of BCP, HAp and β-TCP with rough surface and varying size without using solutions or additives. The method developed is based on a mechanical continuous movement of the particles, relying on the normal ability of the ceramic powders to aggregate themselves while rolling in a cylindrical container for long periods. The physical forces involved in the process, gravity, particle attraction, centripetal force and shocking make the ceramic rounds with golf ball appearance on its surface. With this method it was possible obtain PCS with 30% of porosity with rough surface and size between 1 to 4 mm in diameter.

Abstract: In this study, a nanofibrous poly (L-lactic acid) (PLLA) scaffold reinforced by Hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP) was fabricated using the thermally induced phase separation method. The composite scaffold morphology showed a nanofibrous PLLA matrix and evenly distributed β-TCP/HAP particles. The composite scaffold had interconnective micropores and the pore size ranged 2-10 μm. Introducing β-TCP/HAP particles into PLLA matrix significantly improved the mechanical properties of the composite scaffold. In summary, the new composite scaffolds show a great deal promise for use in bone tissue engineering.

Abstract: Hydroxyapatite (HAp) is one of the most versatile materials used for implantation purpose due to its similarity to natural bone material with a composition around 70% of our bone. Not only that, it is regarded as attractive biomedical materials because of their outstanding bioactivities and non toxicity. The purposes of this particular project are mainly to produce HAp powder by utilizing eggshell waste as its main raw material as well as to study the effectiveness of eggshell substitution in HAp on mechanical behaviour. The process involves drying and thermal decomposition of eggshell followed by hydrothermal reaction at low temperature with di-ammonium hydrogen phosphate and water. After that, the next process that takes place will involve compacting of the powder at pressure of 80 kg/cm²and sintering at temperature of 900-1300oC. Therefore, by using the suitable synthesizing method together with the workable sintering schedule for each synthesizing process, the optimized microstructure and properties of sintered HAp can be prepared.

Abstract: α-TCP/HAp functionally graded porous beads were prepared for use as a scaffold for bone regeneration. In this research, porous beads which have compositionally graded layer, from TCP of inner area to HAp of surface area, were fabricated. It is known that the dissolution rate of TCP is fast in compare with that of HAp in living body, thus the inner area would dissolve prior to the surface area. These beads to allow the penetration of cells and blood vessel into the inner area of beads following new bone regeneration. At present, conditions to fabricate the functionally graded porous beads have been established already, and experiments using cells [MC3T3-E1] are in progress.

Abstract: In this experiment, the copper-containing wastewater was adsorbed by HAP which was prepared by high temperature calcination after high temperature cooking fish scales. By the single factor experiments and orthogonal experiments, the optimal conditions were as follows: the initial concentration of copper ion was 200mg/L,the dosage of HAP was 0.2g,the reaction time was 30min,and pH was 5. The maximum removal efficiency was 98.23%.