L. Papadopoulou

Geochemistry of beach sands from Sithonia Peninsula (Chalkidiki, Northern Greece)

Thirty beach sand samples from the granitic shoreline of the Sithonia Plutonic Complex (SPC) were analyzed for their REE and major element contents. The obtained results are compared with the adjacent SPC rock-types, in order to determine any enrichments or depletions. Among the samples enriched in REE, three are seasonal deposits of heavy minerals and their concentrations are controlled by the action of sea-waves. The available geochemical characteristics were also used to confirm the parental rocks of the beach sands, which are the SPC rock-types. The heavy fractions (total, total magnetic and total non-magnetic) of the beach sands were correlated with the REE concentrations, revealing a strong correlation between the heavy non-magnetic fraction and REE content. Among the minerals of the heavy non-magnetic fraction, monazite seems to control the REE content in the heavy mineral-enriched samples, whereas in the rest of the samples allanite, belonging to the heavy magnetic fraction may be the most important REE mineral.

Effective Cell Growth Potential of Mg-Based Bioceramic Scaffolds towards Targeted Dentin Regeneration

SUMMARY New emerging approaches in tissue engineering include incorporation of metal ions involved in various metabolic processes, such as Cu, Zn, Si into bioceramic scaffolds for enhanced cell growth and differentiation of specific cell types. The aim of the present work was to investigate the attachment, morphology, growth and mineralized tissue formation potential of Dental Pulp Stem Cells (DPSCs) seeded into Mg-based glassceramic scaffolds with incorporated Zn and Cu ions. Bioceramic scaffolds containing Si 60%, Ca 30%, Mg 7.5% and either Zn or Cu 2.5%, sintered at different temperatures were synthesized by the foam replica technique and seeded with DPSCs for up to 21 days. Scanning Electron Microscopy with associated Energy Dispersive Spectroscopy (SEM-EDS) was used to evaluate their ability to support the DPSCs’s attachment and proliferation, while the structure of the seeded scaffolds was investigated by X-Ray Diffraction Analysis (XRD). Zn-doped bioceramic scaffolds promoted the attachment and growth of human DPSCs, while identically fabricated scaffolds doped with Cu showed a cytotoxic behaviour, irrespective of the sintering temperature. A mineralized tissue with apatite-like structure was formed on both Cu-doped scaffolds and only on those Zn-doped scaffolds heat-treated at lower temperatures. Sol-gel derived Zn-doped scaffolds sintered at 890oC support DPSC growth and apatite-like tissue formation, which renders them as promising candidates towards dental tissue regeneration.

Using detrital garnets to determine provenance: a case study from the Vertiskos Unit (Serbomacedonian Massif, N. Greece)

Garnet single crystals of several millimeters in diameter were collected from the uppermost horizon of a soil profile developing immediately on the gneissic rocks of the Vertiskos Unit of the Serbomacedonian Massif in northern Greece. The garnets were analyzed for major elements by EDS analyzer mounted on a scanning electron microscope, and the obtained data were utilized to determine their source rocks. Bivariate diagrams, spider diagrams as well as statistical analysis were used in order to correlate and compare the garnet composition of the basement rocks of the Vertiskos Unit with the existing reference data. This case study demonstrates the difficulty in assigning a source rock to sediment, using only the chemical compositional of detrital garnet. Direct linking of the detrital garnets and the outcropping rocks is not always possible despite well documented outcrop lithologies. This is largely due to a complex metamorphic evolution that leads to overlapping compositions between garnets originating from different lithologies that have undergone similar metamorphic processes and alteration effects.

Characterization and In Vitro Bioactivity Study of Ternary Glass-ceramic Coatings

The aim of the present study was to test the in vitro bioactive behavior of two new ternary mixtures consisting of a glass-ceramic porcelain, a bioactive glass and alumina (PBA) as coatings on dental glass ceramic substrates. They consisted of bioactive glassin the system SiO2-Na2O-CaO-P2O5-, powder from a leucite-fluorapatite glass ceramic and γ-Al2O3 in 5042.5-7.5 wt % respectively, while coatings with the same two components in 50-50 wt % ratio, without Al2O3, served as control. The characterization of the coatings was performed by Scanning Microscopy (SEM-EDS), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD). The in vitro bioactivity was tested in Simulated Body Fluid (SBF) and the surfaces of reacted specimens were examined by SEM and FTIR. All coatings presented rough surface, while FTIR spectra revealed the characteristic peaks of the crystallized phases in the bioactive glass network and dental glass ceramic, i.e. Sodium Calcium Silicate (Na4Ca4Si6O18), Leucite (KAlSi2O6) and Fluorapatite (Ca5(PO4)3F), and furthermore the very limited participation of Al in the bioactive glass network. In the coatings the main phases detected by XRD were, also, Na4Ca4Si6O18 and Leucite, dispersed in an amorphous glassy matrix. Furthermore, a transformation of γ-Al2O3 to δ-Al2O3 was observed and a new phase of Nepheline (Na7.15Al7.2Si8.8O32) was detected in traces. Apatite was developed sporadically on the surfaces of the PBA coatings after 30 days in SBF. These results demonstrate a slight retardation of bioactive response of the coatings of the ternary mixtures compared to dual ones consisting of dental glass ceramic and bioactive glass. The incorporation of Al2O3 can enhance the mechanical properties without a substantial degradation of bioactivity. This finding renders these coatings as promising composite materials for potential dental applications. INTRODUCTION A bioactive surface on inert dental ceramics can be achieved through the application of thin bioactive coatings [1]. Bioactive glasses exhibit excellent biocompatibility in the body, but although bioactive glass incorporation in dental porcelain has been reported to produce bioactive mixtures, it has a negative effect on its mechanical properties, as it is weak, brittle, shatters easily and presents high solubility [2,3]. Thus, most often, they are used in conjunction with other strengthening materials. Improvements of both mechanical properties and solubility can be achieved through a process of mixing glass bioactive with other strong and stable materials such as Al2O3 [4]. Al2O3 has good mechanical properties as compared to bioactive glass, and exhibits extremely high stability with human tissues [5]. The aim of the present study was to test the in vitro bioactive behavior of new ternary mixtures as coatings on dental glass ceramic substrates. Mater. Res. Soc. Symp. Proc. Vol. 1054