Papers by Keyword: Bioactive

Abstract: The aim of this work was to analyze the effect of using rice husk ash (RHA) and bovine bone as raw materials of glass-ceramics based on the SiO₂-Na₂O-CaO-P₂O₅ system on their physical, mechanical properties and bioactivity. All of the investigated compositions were prepared by melting the glass mixtures at 1300°C for 3 h. The resulting glass samples were heated at different temperatures ranging from 600 to 1000°C with fixed dwell-time for 2 h for crystallization. Phase identification of the prepared glass ceramics was carried out by X-Ray diffraction (XRD) and scanning electron microscope (SEM) techniques. In addition, in vitro test was carried out in stimulated body fluid (SBF). Differential thermal analysis (DTA) showed that the glass transition occurred at 505°C and crystallization at 700°C. The main crystalline phase form in most glass ceramics is a sodium calcium silicate. The optimum heat treatment temperature, at which the maximum mechanical value (620 HV) could be obtained, is around 1000°C. After incubation in SBF for 7 days, all of the samples show good bioactivity in vitro, as evident by the formation of bone like apatite phase.

Abstract: Apatite-wollastonite bioactive glass-ceramic scaffolds were fabricated from the SiO₂-CaO-P₂O₅ MgO-CaF₂ glass system by controlled crystallization between 800 and 1200C of the melted and quenched glass powder. Wood powder with controlled particle size distribution was used to obtain bioactive glass-ceramic scaffolds by burning-out process during crystallization of glass. Bioactive phases of apatite and wollastonite were found in all crystallized samples but the relative amount depended on the crystallization temperature. The bioactivity was studied via simulated body fluid (SBF) solution from 2 to 12 weeks. After soaking for 2 weeks, a porous hydroxyl-carbonate apatite (HCA) layer formed at the SBF-glass ceramic interface and the HCA layer thickness increased at longer soaking periods. This study led to a promising platform for hard tissue engineering.

Abstract: Formation of hydroxyapatite (HAp) in simulated body fluid (SBF) on heated nacre has been examined. Nacre is known as composite layer of aragonite platelets and organic materials. Nacre was obtained from the shell of Akoya pearl oyster after removing its prismatic layer. The nacre was heated up to 300°C in air and then soaked in SBF. Nacre heated at 300°C lost iridescent color and became brittle, implying that organic materials which plays a role as glue between aragonite platelets mostly disappeared by heating at 300°C. Formation of HAp particles on nacre in SBF was easier than that on pure Ti. Maximum formation rate of HAp particles was obtained on the nacre heated at 200°C. The amount of HAp particles formed on the nacre heated at 300°C is the smallest. The organic materials in nacre play a critical role for HAp formation on nacre in SBF.

Abstract: The synthesis of nano-scale hydroxyapatite (HAp) could be achieved by using carbon nanofibers (CNFs) as templates. It was shown that both silica fiber and alumina fiber are suitable substrates for the growth of CNFs templates by chemical vapor deposition (CVD) technique. It turned out that the resulting CNFs could act as promising and effective templates for nano-scale deposition of HAp on the fiber surface. However, CNFs obtained from silica fiber performed better than those grown from alumina fiber for uniform deposition of HAp on the surface.

Abstract: In the paper a study of surface composition and fluid sorption by several titanium alloys immersed in a simulated body fluid is presented. Four materials were investigated: pure titanium, two beta titanium alloys and stainless steel 316L. All the materials were prepared using cold pressing and sintering. Sample plates were submitted to nucleation and growth of calcium phosphates precipitated from SBF solution containing calcium, phosphate and other ions. Analysis with scanning electron microscope has revealed some calcium phosphates aggregates on surfaces of all the alloys. The results indicate that the nucleation and growth of phosphates depend on the alloy composition and the process is more intensive in the case of titanium alloys with niobium additions. On the other hand, this material is characterized by the smallest SBF sorption. Chemical analysis using near infrared spectroscopy indicated a presence of some organic groups on the material surface.

Abstract: Bioactive ceramics have the ability to chemically bond to bone. This class of biomaterials can be used as coatings on metallic implants, alloplastic bone defect fillers and as scaffold for tissue engineering. The most widely used bioactive ceramics are hydroxyapatite, Ca10(PO4)6(OH)2 and tricalcium phosphate, Ca3(PO4)2. This study presents new bioactive ceramics based on Nb2O5 and Ta2O5. These materials were produced from bioinert ceramics chemically activated by an alkali hydrothermal treatment. Scanning electron microscopy, energy dispersion X-ray spectroscopy and X-ray diffraction analyses on samples incubated in simulated body fluid showed the presence of bone-like apatite, confirming that the modified ceramics surface became bioactive.

Abstract: Implant failure due to aseptic loosening is a major complication in total hip arthroplasty. Different implant coatings aim to reduce the risk of implant loosening by anti-infectious, bio-active or wear resistant approaches. The mechanical properties, especially bonding strength and wear resistance, of a Cu-TiO2, CaP and TiN coating were investigated in this study. A scratch test and a standard adhesive test were used to determine the bonding strength of the coatings. To analyse the wear resistance a modified special testing machine was used to evaluate wear with PU-foam and PMMA as counterparts. The investigations showed that all coatings have greater bonding strengths than the minimum required 22 N/mm2 for medical implant coatings. Significant differences in total wear were determined during the wear tests. With the exception of the CaP no removal of the coatings was detected.

Abstract: Autogenous bone grafts are considered to be the gold standard in maxillo-facial surgery. However, drawbacks of donor site morbidity and unpredictable rates of resorbtion often limit their use. In vivo tests have shown that 45S5 bioactive glass particles placed in critical size bone defects lead to regeneration of new bone that has the structural characteristics and architecture of mature trabecular bone. In vitro tests using primary osteoblast cultures have shown that the bioactive glass particles release ionic dissolution products that provide genetic stimuli that control osteoblast cell cycles and lead to rapid growth of mineralized bone nodules. These in vitro and in vivo results led to approval of use of bioactive glass particles and monolithic bioactive glass implants for use in maxillo-facial reconstructions after removal of bone cysts and trauma, as described by several case histories.

Abstract: Porous bioactive thin film on commercially pure titanium substrate was prepared by micro-arc oxidation (MAO) in electrolytic solution, which contained calcium acetate, β-glycerol phosphate disodium salt pentahydrate (β-GP) and lanthanum nitrate. The phases and microstructure of the bioactive films were examined by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectrometer and electron probe microanalysis. The results showed that: (1) porous bioactive films with about 10μm were formed on titanium substrate by MAO; (2) phases of the thin films were hydroxyapatite, anatase and rutile; (3) elements of Ca, P, and Ti of films were identified by EDS.

Abstract: This study examined the bioactive and stability of calcium phosphate- polypyrrole(ppy) composite coatings on titanium alloys by electrochemically deposition in simulated body fluid (SBF). Change of coatings mass and SBF pH during coatings soaked in SBF indicated that ppy reduces the decomposition of coatings. The surface morphology of coatings characterized by SEM showed that the stability of composition coating was superior to that of single coating. XRD indicated that ppy induces CO3 2- enter calcium phosphate coating, which showed that the composite coatings possess better bioactive. Thus, this electrochemical deposition provides an effective method of ppy incorporation at physiological temperature, which can offer excellent bioactive and stability of coatings, with a potential for sustained release of therapeutic agents as required for metallic implant fixation.