Papers by Author: Xanthippi Chatzistavrou

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Authors: Ourania Menti Goudouri, Eleana Kontonasaki, Nikolaos Kantiranis, Xanthippi Chatzistavrou, Lambrini Papadopoulou, Petros Koidis, Konstantinos M. Paraskevopoulos
Abstract: Melt derived bioactive glass- porcelain system is reported to be bioactive but with a slow rate of bioactivity. The aim of this work is to fabricate and characterize bioactive glass/dental porcelain composites produced by the sol-gel method. Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray Diffractometry (XRD) were used to characterize the fabricated materials. The FTIR spectra and the XRD patterns confirm the presence of both constituents in the mixtures, while the dominant crystal phases in bioactive glass/dental porcelain specimens are leucite and wollastonite.
Authors: Xanthippi Chatzistavrou, Konstantinos M. Paraskevopoulos, Vehid Salih, Aldo Roberto Boccaccini, Toshihiro Kasuga
Abstract: The aim of this work was to improve a newly developed family of glass-ceramic composite materials by incorporating silver ions in the ceramic structure, thus developing new Ag-doped materials with the ability of showing antibacterial activity for dental applications. Two different sol-gel methodologies were applied for the fabrication of colorless, homogenous and chemically durable materials which can slowly release silver ion for relatively long periods. Both methods led to the successful development of Ag-doped glass-ceramics with silver ions incorporated in the structure that can slowly release in buffer solution, during a period of 45 days. The potential, application of these materials involve the development of bioactive surfaces on dental substrates which can seal the marginal gap creating a bacterial free environment finally supporting the success of dental restorations.
Authors: Xanthippi Chatzistavrou, Nikolaos Kantiranis, Lambrini Papadopoulou, Eleana Kontonasaki, Aldo Roberto Boccaccini, Petros Koidis, Konstantinos M. Paraskevopoulos
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.
Authors: Ourania Menti Goudouri, Eleana Kontonasaki, Xanthippi Chatzistavrou, Lambrini Papadopoulou, Petros Koidis, Konstantinos M. Paraskevopoulos
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.
Authors: Ourania Menti Goudouri, Eleni Theodosoglou, Anna Theocharidou, Eleana Kontonasaki, Lambrini Papadopoulou, Xanthippi Chatzistavrou, Petros Koidis, Konstantinos M. Paraskevopoulos
Abstract: Scaffold-based tooth engineering is currently the most popular approach towards replacing dental tissues or even engineering a bio-tooth. Although, various scaffold materials have been employed in tooth regeneration, the scaffold-based tooth design has, until now, achieved only limited success. Recently, bioactive Mg-based ceramics have attracted interest as Mg plays an important role on skeletal metabolism and affects the quality and structure of hard dental tissues. Mg has been reported to improve the mechanical properties of calcium phosphate ceramics, control biodegradation rate and stabilize the cell-material interface improving cell attachment and growth. The aim of this study was the development of an experimental Mg-based ceramic material, with enhanced bioactivity and adequate mechanical properties, in order to be potentially used in dental tissue regeneration. The Mg-based ceramic was prepared by the sol-gel method, while the stabilization was performed at 1300, 1400 and 1450oC in order a fully crystalline material to be obtained. The characterization of the materials -before and after immersion is Simulated Body Fluid (SBF)- was performed by Fourier Tranform Infrared Spectroscopy (FTIR), X-Ray Diffractometry (XRD) and Scanning Electron Microscopy associated with an EDS analyzer (SEM-EDS), while the flexural strength of uniaxially pressed pellets was measured using a universal testing machine for 3- point bending tests (Instron 3344). FTIR spectra and XRD patterns of all powder samples before immersion in SBF solution confirmed the presence of three crystalline phases; akermanite, merwinite and diopside. The onset of apatite formation on the surface of all powders was observed even after three days of immersion, while the apatite formation on the surface of the sintered pellets was slightly delayed. Flexural strength values were in the range of 30Mpa. In conclusion, Mg-based glass-ceramics attain adequate mechanical integrity and high rate of bioactivity and could be potentially used in the construction of ceramic scaffolds for dental tissue regeneration.
Authors: Xanthippi Chatzistavrou, E. Hatzistavrou, Nikolaos Kantiranis, Lambrini Papadopoulou, Eleana Kontonasaki, K. Chrissafis, Petros Koidis, Konstantinos M. Paraskevopoulos, Aldo Roberto Boccaccini
Abstract: The aim of this study was the fabrication using a sol-gel technique of a new glass-ceramic with potential use in dental applications. The characterization of the composition and microstructural properties of the produced material confirmed the similarity between the new sol-gel derived glass-ceramic and a commercial leucite based fluorapatite dental glass-ceramic. The produced material has potential application in dental restorations and it is expected to exhibit better control of composition, microstructure and properties due to the intrinsic advantages of the sol-gel preparation method.
Authors: Xanthippi Chatzistavrou, K. Chrissafis, Eleana Kontonasaki, T. Zorba, Petros Koidis, Konstantinos M. Paraskevopoulos
Abstract: Three-dimensionally ordered materials containing hydroxyapatite (HAp) as well as Bioglass® (BG) have been prepared in form of pellets and have been examined the effects of BG addition -in combination with a heat treatment process- on biological properties of composite HAp/BG. The investigation of the bioactive behavior of sintered and unheated biphasic mixtures and the deviations from pure HAp was performed by FTIR spectroscopy and Differential Thermal Analysis. It was observed the appearance of new phases on sintered composite pellets, while a faster biological HAp layer formation was detected, on the composite unheated pellets’ surface than on pure HAp and sintered composite pellets, currently leading to increased bioactivity.
Authors: E. Hatzistavrou, Xanthippi Chatzistavrou, Lambrini Papadopoulou, Nikolaos Kantiranis, K. Chrissafis, Aldo Roberto Boccaccini, Konstantinos M. Paraskevopoulos
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.
Authors: Ourania Menti Goudouri, Xanthippi Chatzistavrou, Eleana Kontonasaki, Nikolaos Kantiranis, Lambrini Papadopoulou, K. Chrissafis, Konstantinos M. Paraskevopoulos
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.
Authors: Eleana Kontonasaki, Nikolaos Kantiranis, Xanthippi Chatzistavrou, Lambrini Papadopoulou, Konstantinos M. Paraskevopoulos, Petros Koidis
Abstract: Dental ceramic-bioactive glass composites support the attachment and proliferation of human periodontal ligament cells, while their immersion in a simulated body fluid (SBF) results in the precipitation of biological hydroxyapatite further supporting cell proliferation [1]. The aim of the present study was the comparative evaluation of three dental ceramic-bioactive glass composites’ crystal structure relative to bioactive glass amount and the evaluation of their bioactivity. All composites consisted of leucite and Na2CaSi3O9 crystals dispersed in amorphous glassy matrix. Leucite and Na2CaSi3O9 crystals decreased significantly in all composites with the highest amount of dental ceramic, which did not precipitated apatite during the examined immersion time in SBF. An increase of Na2CaSi3O9 crystals in the composites with the highest amount of bioactive glass resulted in faster apatite formation. Increased bioactivity was linearly correlated to increased amount of bioactive glass.
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