Papers by Author: Ourania Menti Goudouri

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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: George Theodorou, Ourania Menti Goudouri, Lambrini Papadopoulou, Nikolaos Kantiranis, Subramaniam Yugeswaran, Akira Kobayashi, Konstantinos M. Paraskevopoulos
Abstract: The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has been widely investigated as the HA coating can achieve the firm and direct biological fixation with the surrounding bone tissue. It is shown in previous studies that the mechanical properties of HA coatings are improved by the addition of ZrO2 particles during the deposition of the coating on the substrate. Subsequently, the cohesive and adhesive strengths of plasma-sprayed hydroxyapatite (HA) coatings were strengthened by the ZrO2 particles addition as a reinforcing agent in the HA coating (HA+ZrO2 composite coating). The aim of the present work is to investigate and evaluate the in vitro bioactivity assessment of HA and HA/ZrO2 coatings, on stainless steel substrate, soaked in c-SBF, in order to study and compare their biological responses. The coatings were produced using vapor plasma spraying (VPS). The characterization of the surface of the coatings before and after soaking in SBF solution was performed using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray Diffraction analysis (XRD). All samples were smoothed before insertion in the medium and the in vitro bioactivity of all coating samples was tested in conventional Simulated Body Fluid (c-SBF) solution for various immersion times.
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: 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: George S. Polymeris, Ourania Menti Goudouri, Konstantinos M. Paraskevopoulos, George Kitis
Abstract: Results of the present study provide strong indications towards the effective application of the 110oC Thermoluminescence (TL) peak in discriminating between different bioactive responses for the case of the 58S bioactive glass. The in vitro bioactivity of this glass in the form of powder in SBF solution was tested for various immersion times, ranging between 0 and 6 days. This TL peak is ubiquitously present in all 58S samples, for all immersion times. The intensity of the110oC TL peak was proven to be very sensitive to the different bioactive responses, indicating a strongly decreasing pattern with increasing immersion time in SBF, easily identifying thus the loss of silica. This loss is reflected to the decrease of the 110oC TL peak intensity, which appears to be fast even for the shorter immersion times. The 110oC TL glow peak intensity and sensitization could also be yielding a time scale regarding the beginning of some among the several stages included in the bioactivity sequence.
Authors: M. Manda, Ourania Menti Goudouri, Lambrini Papadopoulou, Nikolaos Kantiranis, T. Zorba, K. Chrissafis, Konstantinos M. Paraskevopoulos, Petros Koidis
Abstract: End temperature of the firing cycle, during processing of dental ceramics, directs the interaction of both sintering and crystallization pathways, tailoring physicochemical properties and bioactivity. Thus, the purpose of the present study was to investigate the influence of end temperature over the structural properties and composition, along with the bioactive behavior of dental porcelain, modified by bioactive glass. Sol-gel derived specimens of bioactive glass (58S)- commercial dental porcelain composites synthesized (BP) and underwent firing cycles at the crystallization temperature (Tc=1040oC) and the temperature just below the melting range (Tm=1080oC), as the composite material. The recommended temperature for the commercial porcelain (Ta=930oC) was examined, too. All specimens were characterized using X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM). The assessment of bioactivity was performed in vitro, via the detection of apatite layer development. The well-defined particles, observed by SEM, at 930oC, developed contact formation during the stage of neck growth at 1040oC and 1080oC, indicating the initiation of sintering process. Increasing temperature, the complex porei network became smoother, while spherical and closed porei were evident. FTIR revealed the predominance of wollastonite at the increased temperatures, along with the appearance of cristobalite, while XRD confirmed the results. Finally, the in vitro tests evidenced the bioactivity of the specimens independently of the final temperature, though the increased temperature caused delayed apatite layer formation on their surface. The, microstructural and chemical evolution of the studied composite is temperature-dependent. Increased temperature favored the sintering process initiation, along with the surface crystallization, which delays bioactivity.
Authors: Ourania Menti Goudouri, Maria Perissi, Eleni Theodosoglou, Lambrini Papadopoulou, Xanthippi Chatzistavrou, Eleana Kontonasaki, Petros Koidis, Konstantinos M. Paraskevopoulos
Abstract: In most biphasic composite systems consisting of sol-gel derived bioactive glass and a second system that is usually used as a reinforcing agent, thorough stirring is necessary to prevent the precipitation of the grains of the second system. Consequently, the aim of this work is to investigate the impact of various stirring rates on the crystallinity and bioactivity of a bioactive glass in the system 58S. Sol-gel-derived bioactive glass (58S) was produced as described in literature. During the gelation, stirring rates of 0, 200, 400, 600 and 800 rpms were applied producing, respectively, the corresponding glass powders. The in vitro bioactivity of the powders was tested in Simulated Body Fluid (SBF) for various immersion times, while the solution was renewed after 6h, 24h and then every 2 days. Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray Diffractometry (XRD) were used to characterize all materials before and after immersion in SBF solution. FTIR and XRD measurements of all powders revealed mainly the formation of an amorphous glass, while the main crystalline phase was identified to be Ca2SiO4. After immersion in SBF solution for 12h, SEM microphotographs revealed apatite formation on the surface of all samples, while FTIR and XRD confirmed the aforementioned findings. Furthermore, since EDS analysis proved a mean molar Ca/P ratio of about1.7 after 6 days of immersion of all samples- besides those stirred at 400 and 600rpm- it can be assumed that a thick apatite layer was formed covering the whole surface.
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