Papers by Keyword: Bioactivity

Abstract: Gentamicin sulphate was mixed with two different sol-gel derived calcium silicates (akermanite or wollastonite). Each of the mixtures was isostatically pressed. Samples were immersed in simulated body fluid for 21 days. The presence of the antibiotic showed no effect on the in vitro bioactivity of the ceramics. For evaluating the gentamicin sulphate release, samples were immersed in a phosphate buffered saline solution for different periods of time. Most of the gentamicin sulphate was released during the first 7 days. However, akermanite showed a lower antibiotic release rate than that observed for wollastonite.

Abstract: Apatite nuclei were dispersed in inorganic binder and the apatite nuclei-contained inorganic binder was coated on polyethyleneterephthalate plate. Hydroxyapatite was induced by the apatite nuclei dispersed in the binder and hydroxyapatite layer was formed on the surface of the substrate by soaking in SBF. The hydroxyapatite layer showed high adhesive strength to the substrate.

Abstract: Surface structural change of titanium metal with NaOH and heat treatments and the subsequent soaking in a simulated body fluid (SBF) was investigated by observing cross section of its surface layer by scanning electron microscope. A layer of lathlike phase of sodium hydrogen titanate was formed on the surface of the titanium metal 1 µm in thickness by the NaOH treatment. This was transformed into a layer of lathlike form a little densified of sodium titanate and rutile by the subsequent heat treatment. In SBF, apatite started to precipitate in the interior of the surface lathlike layer, filled the interspaces of the lathlike phases and grew over the surface. This integration of the apatite with the surface lathlike layer might be responsible for the strong bonding of the titanium metal to the living bone.

Abstract: Metals are the most used materials as orthopaedic or dental implants for their excellent mechanical properties. However they are not able to create a natural bonding with the mineralized bone and they could release metallic particles that could finally end in the removal of the implant. A promising alternative to avoid those effects is to protect the implant with a biocompatible coating. In this work there are analyzed two kinds of protective organic-inorganic coatings made by sol gel technique with the adding of silica particles, in order to increase the barrier effect of the coating, and glass-ceramic (GC) particles with the aim of generating bioactivity. X-ray photoelectron spectroscopy (XPS) and electrochemical techniques were used to analyze the bioactive and protective response of this silica reinforced coatings with the adding GC particles applied on surgical grade stainless steel.

Abstract: Thermal treatment of bioactive glasses can affect their microstructure and thus their bioactivity. The aim of this study was the characterization of the thermally treated sol-gel-derived bioactive glass 58S at characteristic temperatures and the dependence of its bioactive behavior on the specific thermal treatment. The thermal behavior of the bioactive glass was studied by thermal analysis (TG/DTA). Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffractometry (XRD) were used for the characterization of the bioactive glass. The bioactive behavior in Simulated Body Fluid (SBF) was examined by Scanning Electron Microscopy (SEM-EDS) and FTIR. The major crystal phases after thermal treatment were Calcium Silicates, Wollastonite and Pseudowollastonite, while all thermally treated samples developed apatite after 48 hours in SBF. A slight enhancement of bioactivity was observed for the samples heated at the temperature range 910-970oC.

Abstract: Sol-gel derived glasses have been reported to express considerably higher bioactivity than melt-derived ones. The use of the sol-gel method for the fabrication of dental ceramic bioactive glass composites has resulted in composites consisting of an amorphous glassy network into which crystals of Calcium Silicate (CS), Wollastonite (W), leucite (Lt) and Fluorapatite (FAp) are dispersed. Thus, the aim of the present study was the investigation of the bioactivity of sol-gel derived dental ceramic/bioactive glass composites, in the form of powders and in thermally treated disk shaped specimens. Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) were used to characterize the reacted products. The sol-gel derived dental glass ceramic composites present high bioactivity compared to the respective melt-derived ones, which is attributed to the higher CaO content and the crystallization of bioactive W and CS crystal phases during the fabrication process. However, the powdered samples presented faster HCAp formation compared to the respective specimens, due to their higher surface energy.

Abstract: In this study new ternary bioactive mixtures were investigated, which are appropriate for applications as coatings on the surface of dental ceramics. The fabrication of mixtures based on the combination of dental ceramic, hydroxyapatite and bioactive glass was demonstrated. The mixtures were characterized by FTIR, XRD and SEM and their bioactive behavior was investigated by immersion in Simulated Body Fluid (SBF). The ternary mixture consisted of a high fusing leucite-feldspathic dental ceramic which exhibited the highest bioactive behavior assigned to the characteristic crystal phases occurring under the specific heat treatment investigated.

Abstract: This work is focused on the bioactive glasses obtained by melting and rapid quenching. Two glasses with mineral composition of: 47% SiO2 - 26% CaO - 21% Na2O - 6% P2O5 and 48% SiO2 - 30% CaO - 18% Na2O - 4% P2O5 were investigated. The aim of this study was to establish the kinetics of HCAp layer formation “in vitro” and to control the adhesion and proliferation cells of the two glasses in contact with osseous cells. Obtained results permit to evaluate their chemical reactivity and their bioactivity after immersion in the SBF-K9. Ionic exchanges between biomaterials and SBF liquid during the “in vitro” experiments highlight the differences of the chemical reactivity and bioactivity of 47S6 and 48S4. The structural basis for the effect of cristallinity on the rates of HCA formation in vitro in favour of glasses was also established. The melt derived 47S6 and 48S4 glasses offer to surgeons new compositions with different bioactivity kinetic that bioglassÒ 45S6 and can be adaptable in some other bony pathology.

Abstract: In this study a ceramic composite with nominal composition 40 wt% Ca3(PO4)2 – 60 wt% CaMg(SiO3)2 was obtained by solid state sintering of compacts of both synthetic fine powders. The ceramic composite showed a fine grained and homogeneous microstructure consisting of CaMg(SiO3)2 and b-Ca3(PO4)2 grains. The results of X-ray diffraction and scanning electron microscopy demonstrated that, during soaking in SBF, the grains of β-Ca3(PO4)2 dissolved preferably than those of CaMg(SiO3)2, leaving a porous surface layer rich in CaMg(SiO3)2. Subsequently, partial dissolution of the remaining CaMg(SiO3)2 occurred and the porous surface of the b-Ca3(PO4)2-CaMg(SiO3)2 ceramic became coated by a bone-like apatite layer after 7 days in SBF.

Abstract: In this study the fabrication and characterization of a novel sol-gel derived HAp-CaO composite material is investigated. The bioactive behavior of the fabricated composite was assessed by immersion studies in SBF. A brittle and weakly crystalline carbonate hydroxyapatite (HCAp) layer was found to develop few hours after the immersion in SBF confirming high bioactivity. The presence of CaO accelerates the formation of HCAp phase.