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- ItemFundamental research on twofold phase formation of apatite solid-solutions and leucite in glass-ceramics(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) van 't Hoen, Christian; Höland, Wolfram; Rheinberger, VolkerIn this study the phase formation of apatites in the multi-component SiO₂-Al₂O₃-Na₂O-K₂O-GaO/SrO-P₂O₅-F system was investigated. Based on a special composition GaO was partially and completely substituted by SrO. Room and high temperature X-ray diffraction (RT- and HT-XRD) and scanning electron microscopy (SEM) were used to characterize the phase formation. The results of this study showed a formation of two different apatite solid-solutions, Sr_(7.3)Ca_(2.7)(PO₄)₆F₂ and Sr₆Ca₄(PO₄)₆F₂ and Sr-apatite Sr₅(PO₄)₃F. Leucite formation is based on surface crystallization. The conclusion is a twofold volume and surface nucleation and crystallization mechanism.
- ItemGlass-ceramics and biomaterials with tailor-made properties(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) Höland, Wolfram; Rheinberger, Volker; Apel, ElkeBased 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.
- ItemDevelopment of bioactive glass-ceramics(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) Apel, Elke; Höland, Wolfram; Rheinberger, VolkerΑ 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.