Papers by Keyword: Calcium Phosphate

Abstract: Electrically conducting polymer containing calcium phosphate coating (ppy/brushite) was made on the Ti-6Al-4V surface by means of electrochemically assisted co-precipitation. This study examined the effects of the electrically conducting polymer on electrochemically assisted co-precipitation of ppy/ brushite onto titanium alloys. Electrochemically assisted co-precipitation of ppy/ brushite coatings resulted in an increase in the thickness and adhesion of coatings compared to those of coatings of single calcium phosphate at the same deposition conditions. The surface morphology of coatings characterized by SEM showed that the morphology of ppy/ brushite was superior to that of brushite. XRD indicated that ppy did not change the phase of brushite. Thus, this electrochemically assisted co-precipitation technique provides an effective method of polypyrrole incorporation at physiological temperature, which can offer excellent thickness, adhesion and structure of coatings, with a potential for sustained release of therapeutic agents as required for metallic implant fixation.

Abstract: The porous structure of calcium phosphate ceramics is one of the essential conditions resulting in bone formation. The porous structure of biphasic HA/β-TCP ceramics was improved by adding microporous porosifer and the porous characteristics such as porosity, pore size and pore size distribution were determined by the mercury intrusion porosimetry, the cell culture in vitro and the animal experiment. By means of SEM and fluorescence decoration, cells were observed firstly attaching the edge of macropores of specimens and the wall of the macropores with micropores when co-cultured with HA/β-TCP ceramics. The specimens were also implanted in dorsal muscles of healthy dogs for 1.5and 3 months. More bone formation in the specimen with microporous porosifer was found by histological observation after taking out. It suggested that the micropores in the walls of macropores of bioceramics had important effect upon their osteoinduction.

Abstract: This work has achieved a novel self-setting biphase porous calcium phosphate cement (CPC). This biphase porous CPC is mainly formed by α-tricalcium phosphate (α-TCP) and β-tricalcium phosphate (β-TCP). The influence of the weight percent (wt%) of β-TCP of the powder was studied. The setting time is mainly 10-30min, and increasing with the weight percent of β-TCP. Powder ray diffraction (XRD) analysis showed that most α-TCP have turned to low-crystallinized HA after immersed in Simulated Body Fluid (SBF) of 37°C for 7 days. SEM observation showed that the resultants are mainly formed with micropores and microcrystallites, and more micropores turned out in cements with more β-TCP after immersed in SBF for 8 weeks.

Abstract: Ca3(PO4)2/ZrO2 dental composite ceramics using for CAD/CAM system were prepared and the effects of weak phases on microstructures and mechanical properties were studied. The results showed that intergranular spreads happened with the increasing Ca3(PO4)2 contents due to the discontinuity of weak interfaces between Zirconia and Calcium phosphate in matrix. So the flexural strength and hardness of the Ca3(PO4)2/ZrO2 composite ceramics were decreased effectively, which improved the machinability of the composites. On the other hand, strong interfaces between Zirconias increased the integrality of the ceramic structures. ZrO2 composite Ceramics with 15% Ca3(PO4)2 were sintered at 1350°C. The flexural strength is 300.44MPa, fracture toughness is 4.36 MPam1/2, and hardness is 6.69 GPa. The cutting exponent of the Ca3(PO4)2/ZrO2 composite ceramics is obviously lower than that of the common commercial Vita Mark II and Dicor MGC ceramics, which shows good mechanical properties and machinability.

Abstract: Calcium phosphate films were coated on commercially pure titanium substrates by radiofrequency magnetron sputtering using β-tricalcium phosphate targets. The films consisted of amorphous calcium phosphate and oxyapatite phases. Immersion tests of the films were carried out in Hanks’ solution and PBS(-), and apatite formation and calcium ion elution from the films were investigated. The titanium cylinders coated with calcium phosphate films were implanted into the mandibles of beagle dogs. These results suggest that coating with calcium phosphate improves the biocompatibility of titanium implants with bone tissue.

Abstract: A nano-micro structured protein/octacalcium phosphate composite coating was prepared by electrochemically-induced deposition (ED) onto titanium surface. The characterizations of XRD, SEM and FT-IR indicate that the as prepared composite coating consists of protein and octacalcium phosphate with a highly and hierarchically porous structure in nano-micro scale, similaring to the natural bone structure.

Abstract: Macroporous biomaterials based on a-tricalcium phosphate (a-TCP) bone cement with porous structures suitable for implantation purposes were prepared in the present work. According to the reversible swelling/deswelling behavior of gelatin at a single temperature or pH, a “self-setting” method that uses gelatin granules as pore formers was developed to process the porous microstructure. By mixing gelatin powder and bone cement powder (BCP), and adding water (1% solution of NaH2PO4×HO) to form pastes which set within 15 to 30 min, this setted cement was then immerged in deionized water of temperature 25°C or 32°C for hydration. During the hydration, the pH of deionized water after cement pastes were introduced at 32°C changed from 8.6 to 7.2 which caused by the transformation of a-TCP to hydroxyapatite (HA). Meanwhile, gelatin particles will swell by water uptake to form large size spheres in cementmatrix. This swelling behavior is sensitive to the variation of pH value. After hydration for 4 day, a body containing gelatin gel spheres was obtained. Then heating the deionized water to temperature 50°C, gelatin spheres in cement matrix were solved and porous microstructure composed of larger pore sizes corresponding approximately to the average size of the swelling gelatin granules was obtained. The porous bodies by this technique were found to have tractable and interconnected porosity in the range of 60~84%, with typical pore sizes ranging from 100~300 microns. This new processing technique can be used in the manufacture of unsintered biomaterials.

Abstract: Gypsum powders and calcium phosphate/gypsum powders were synthesized by wet method. The influences of the pH and temperature on the morphology of the gypsum crystal were studied by light microscopy. The effects of the initial calcium/phosphorus molar ratio and the pH of the solution on the microstructure and phase composition of the calcium phosphate/gypsum composite powders were studied by scanning electron microscopy and X-ray diffractometry. The results show that both temperature and pH value had influence on the crystal shape of gypsum and the pH value was the predominant parameter for the particle shape and phase composition of the composite powders.

Abstract: Macroporous biphasic calcium phosphate bioceramics, for use as bone substitutes, have been fabricated by cold isostatically pressing and conventional sintering, using naphtalen or saccharose particles to produce macropores. The resulting ceramics, composite materials made of hydroxyapatite and b-tricalcium phosphate containing ~ 45% macropores and ~ 25% micropores, have been submitted to compression and three-point bending tests, toughness tests by single-edge-notched-bending, and spherical indentation tests. A new model is established to describe mechanical properties as a function of the amount and morphology of porosity, and propositions are made to optimise the fabrication procedure. Finally, those highly porous ceramics, although very brittle, exhibit a damage-tolerant contact behaviour, due to the compaction of the porous body under the indenter.

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