Browsing by Author "Apel, Elke"

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    Development of bioactive glass-ceramics
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) Apel, Elke; Höland, Wolfram; Rheinberger, Volker
    A bioactive glass-ceramic with rhenanite, NaCaPO₄, was developed in the SiO₂ - Na₂O - CaO - P₂O₅ - F System. Crystallization and microstructure were determined by room temperature X-ray diffraction (RT-XRD) and scanning electron microscopy (SEM) methods. The surface properties of the monolithic material and its surface reactivity were investigated after immersion in simulated body fluid (SBF) for 1 to 10 days. The layer that formed was identified as hydroxyapatite (HA) using surface sensitive analytical methods. Ion exchange processes of Ca²⁺ and phosphate ions were determined. HA formed on the surface of the samples within 48 hours. An open-porous scaffold was prepared using the polymer sponge method. Based on the main results of the investigation, we conclude that rhenanite glass-ceramics possess very good bioactive properties.
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    Glass-ceramics and biomaterials with tailor-made properties
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) Höland, Wolfram; Rheinberger, Volker; Apel, Elke
    Based on the fundamental theories of materials development by Professor Kreidl, the developments of the authors are presented four types of glass-ceramics as biomaterials used in dentistry. These materials have been developed since the Norbert Kreidl Symposium in 1994. They are leucite glass-ceramics with new properties, as well as high-strength glass-ceramics and materials with particular optical brilliance. Furthermore, new approaches using surface-active materials are discussed.
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    Microstructure formation and surface properties of a rhenanite-type glass-ceramic containing 6.0 wt% P2O5
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2005) Höland, Marlies; Dommann, Alex; Höland, Wolfram; Apel, Elke; Rheinberger, Volker
    The aim of this report was to characterize the microstructure formation of a rhenanite, NaCaPO4, glass-ceramic and to determine its surface properties. The composition of the material was (in wt%) 58.0 SiO2, 6.0 P2O5, 22.8 Na2O, 12.9 CaO, and 0.3 F. Nucleation and crystallization of the monolithic base glass was carried out at temperatures between 650 and 1000°C for one hour. To characterize the different microstructures of the glass-ceramics using scanning electron microscopy (SEM), a special sample with phosphoric acid was prepared. The control of microstructure formation resulted in the precipitation of isolated α-rhenanite crystals with a crystal size of 40 nm up to 1 μm and a crystal number density of 20 to more than 2000 particles per 100 μm2. The α-phase transformed into the β-phase at approximately 690 °C. The surface properties were determined by soaking the specimens in simulated body fluid for up to 10 d. In the process, the glass-ceramics exhibited a high surface activity. Morphological investigations after soaking showed ball-shaped hydroxyapatite-type crystals consisting of two half shells. The authors concluded that rhenanite crystals acted as heterogeneous nuclei for hydroxyapatite on the surface of the bioactive glass-ceramics. Therefore, this material was assumed to have the ability to bond to living bone.