Home About us Contact
|
Home About us Contact | ||
|
|
||
HA Layer (ha + layer)
Selected AbstractsCalcium-phosphate surface coating by casting to improve bioactivity of titaniumJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 5 2001Taiji Sohmura Abstract In order to improve the bioactivity of titanium, an original surface treatment was attempted with the use of a casting technique was attempted. Pure titanium was cast into a special graphite mold in which the cavity wall was coated with hydroxyapatite (HA) powder. According to analyses of X-ray diffraction and EDX, the existence of HA and CaO and uptake of Ca and P on the surface of the titanium castings were identified. By immersing the specimen in Hank's solution, the concentrations of Ca and P on the surface increased with immersion time, and the formation of a thin layer with characteristics of spherical HA precipitates was observed after 1 week. The concentrations of Ca and P elements and the Ca/P ratio on the HA layer increased with immersion time. The formation of the HA layer on the titanium cast by this treatment was significantly accelerated compared with pure titanium. The present surface treatment of Ti is expected to improve early bone fixation of Ti implants. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 478,485, 2001 [source] A resorbable porous ceramic composite bone graft substitute in a rabbit metaphyseal defect modelJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2003W. R. Walsh The success of converted corals as a bone graft substitute relies on a complex sequence of events of vascular ingrowth, differentiation of osteoprogenitor cells, bone remodeling and graft resorption occurring together with host bone ingrowth into and onto the porous coralline microstructure or voids left behind during resorption. This study examined the resorption rates and bone infiltration into a family of resorbable porous ceramic placed bilaterally in critical sized defects in the tibial metaphyseal,diaphyseal of rabbits. The ceramics are made resorbable by partially converting the calcium carbonate of corals to form a hydroxyapatite (HA) layer on all surfaces. Attempts have been made to control the resorption rate of the implant by varying the HA thickness. New bone was observed at the periosteal and endosteal cortices, which flowed into the centre of the defect supporting the osteoconductive nature of partially converted corals. The combination of an HA layer and calcium carbonate core provides a composite bone graft substitute for new tissue integration. The HA-calcium carbonate composite demonstrated an initial resorption of the inner calcium carbonate phase but the overall implant resorption and bone ingrowth behaviour did not differ with HA thickness. © 2003 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Conversion of Bioactive Borosilicate Glass to Multilayered Hydroxyapatite in Dilute Phosphate SolutionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2007Yadong Li The conversion of a bioactive borosilicate glass in aqueous phosphate solution was observed to produce vastly different reaction kinetics and hydroxyapatite (HA) microstructures, depending on whether the glass was reacted continuously or intermittently in the solution. Particles (150,300 ,m) of a borosilicate glass (designated H12) were reacted continuously or intermittently in 0.25M K2HPO4 solution with a starting pH value of 7.0 at 37°C. The conversion kinetics of the glass particles to HA were determined from weight loss measurements. Structural and compositional changes resulting from the conversion reaction were characterized using scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray analysis, and Fourier transform infrared spectroscopy. For conversion experiments carried out intermittently (12,24 h intervals, followed by drying), faster reaction kinetics and a unique multilayered microstructure, consisting of alternating layers of HA and an amorphous SiO2 -rich material with nearly uniform thickness (2,3 ,m), were observed. On the other hand, particles reacted continuously in the phosphate solution for the same total time converted more slowly and produced a single HA layer. The kinetics and mechanism of forming HA under the intermittent and continuous reaction conditions are described and compared with those for bioactive silicate and borate glasses studied in previous work. [source] Mechanical Activation of Tetracalcium PhosphateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2004Uwe Gbureck It was found that prolonged high-energy ball-milling of Hilgenstokite (tetracalcium phosphate, TTCP) resulted in a decrease in both particle and crystallite size, leading to a mechanical activation of the compound. This mechanically activated material demonstrated a high reactivity such that, in contrast to highly crystalline TTCP, a setting reaction with water to nanocrystalline hydroxyapatite (HA) and Ca(OH)2 could be achieved at 37°C. However, crystalline TTCP is practically unreactive at physiologic temperatures because of the formation of a thin HA layer on the particle surface preventing further reaction. [source] Synthesis, Characterization, and In Vitro Bioactivity of Sol-Gel-Derived Zn, Mg, and Zn-Mg Co-Doped Bioactive GlassesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 7 2010M. Erol Abstract Bioactive glasses in the systems CaO-SiO2 -P2O5 -ZnO, CaO-SiO2 -P2O5 -MgO, and CaO-SiO2 -P2O5 -MgO-ZnO were prepared and characterized. Bioactive glass powders were produced by the sol-gel method. The prepared bioactive glass powders were immersed in a simulated body fluid (SBF) for periods of up to 28,days at 310,K to investigate the bioactivity of the produced samples. Inductively coupled plasma (ICP) and ultraviolet (UV) spectroscopic techniques were used to detect changes in the SBF composition. X-Ray diffraction (XRD) was utilized to recognize and confirm the formation of a hydroxyapatite (HA) layer on the bioactive glass powders. Microstructural characterizations of the bioactive glass samples were investigated by scanning electron microscopy (SEM) techniques. Density, porosity, and surface area values of bioactive glass powders were also determined in order to characterize the textural properties of the samples. The results revealed the growth of an HA layer on the surface of the bioactive glass samples. MgO in the glass sample increases the rate of formation of an HA layer while ZnO in the glass slows it down. [source] Multi-walled Carbon Nanotube-Reinforced Hydroxyapatite Layers on Ti6Al4V Medical Implants by Electrophoretic Deposition (EPD),ADVANCED ENGINEERING MATERIALS, Issue 1-2 2008C. Kaya Sol-gel synthesised nano-size hydroxyapatite (HA) powders were dispersed in water-based suspensions with the addition of multi-walled carbon nanotubes. Ti6Al4V medical alloys were coated with monolithic and carbon nanotube-reinforced HA using electrophoretic deposition (EPD) in an attempt to control deposit structure and thickness. It was shown that the sintering temperature of the deposited HA layers was significantly lowered by the use of sinter active nano-powders. Moreover the addition of carbon nanotubes increased the bonding strength of the EPD-formed layers to the metallic substrate. The cost-effective EPD technique used in the present work has high industrial potential for coating metallic medical implants with composite bioactive layers. [source] Carbon Nanotube Coatings on Bioglass-Based Tissue Engineering ScaffoldsADVANCED FUNCTIONAL MATERIALS, Issue 15 2007R. Boccaccini Abstract The coating of highly porous Bioglass® based 3D scaffolds with multi-walled carbon nanotubes (CNT) was investigated. Foam like Bioglass® scaffolds were fabricated by the replica technique and electrophoretic deposition was used to deposit homogeneous layers of CNT throughout the scaffold pore structure. The optimal experimental conditions were determined to be: applied voltage 15,V and deposition time 20 minutes, utilizing a concentrated aqueous suspension of CNT with addition of a surfactant and iodine. The scaffold pore structure remained invariant after the CNT coating, as assessed by SEM. The incorporation of CNTs induced a nanostructured internal surface of the pores which is thought to be beneficial for osteoblast cell attachment and proliferation. Bioactivity of the scaffolds was assessed by immersion studies in simulated body fluid (SBF) for periods of up to 2 weeks and the subsequent determination of hydroxyapatite (HA) formation. The presence of CNTs can enhance the bioactive behaviour of the scaffolds since CNTs can serve as template for the ordered formation of a nanostructured HA layers, which does not occur on uncoated Bioglass® surfaces. [source] Hydrothermal crystallization of carbonate-containing hydroxyapatite coatings prepared by radiofrequency-magnetron sputtering methodJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2007Satoshi Nakamura Abstract Carbonate-containing hydroxyapatite (HA) films were prepared by low-temperature hydrothermal annealing from carbonate-containing calcium phosphate amorphous coatings on titanium substrates. The biocompatibility of the carbonate-containing HA layers was estimated by in vitro tests using simulated body fluid (SBF). Precursory amorphous coatings were deposited with rf-magnetron sputtering apparatus, using calcium phosphate glass target in Ar/CO2 atmosphere. The carbonate-containing HA coatings were successfully formed by the annealing at above 130°C for 20 h. On the basis of SEM observation, about 2-,m thickness films coated rigidly were durable enough for the hydrothermal treatment. The coating layer was revealed to consist of single phase of PO4, and OH, partially carbonated HA by XRD and IR analyses. Overgrowing of bone-like apatite layers on the carbonate-containing HA surfaces in the SBF implied that the obtained films acquired a sufficient osteoconductivity, while it was still unclear that activity was enhanced, compared to pure HA coatings. The low-temperature hydrothermal annealing method was effective for preparation of rigid HA coatings on titanium as well as modification of their chemical compositions. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007 [source] | ||||||||||