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Radiopaque Strontium Fluoroapatite Glass-Ceramics

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      Abstract

      The controlled precipitation of strontium fluoroapatite crystals was studied in four base glass compositions derived from the SiO 2–Al 2O 3–Y 2O 3–SrO–Na 2O–K 2O/Rb 2O/Cs 2O–P 2O 5–F system. The crystal phase formation of these glasses and the main properties of the glass-ceramics, such as thermal and optical properties and radiopacity were compared with a fifth, a reference glass-ceramic. The reference glass-ceramic was characterized as Ca-fluoroapatite glass-ceramic. The four strontium fluoroapatite glass-ceramics showed the following crystal phases: (a) Sr 5(PO 4) 3F – leucite, KAlSi 2O 6, (b) Sr 5(PO 4) 3F – leucite, KAlSi 2O 6, and nano-sized NaSrPO 4, (c) Sr 5(PO 4) 3F – pollucite, CsAlSi 2O 6, and nano-sized NaSrPO 4, and (d) Sr 5(PO 4) 3F – Rb-leucite, RbAlSi 2O 6, and nano-sized NaSrPO 4. The proof of crystal phase formation was possible by X-ray diffraction. The microstructures, which were studied using scanning electron microscopy, demonstrated a uniform distribution of the crystals in the glass matrix. The Sr-fluoroapatites were precipitated based on an internal crystallization process, and the crystals demonstrated a needle-like morphology. The study of the crystal growth of needle-like Sr-fluoroapatites gave a clear evidence of an Ostwald ripening mechanism. The formation of leucite, pollucite, and Rb-leucite was based on a surface crystallization mechanism. Therefore, a twofold crystallization mechanism was successfully applied to develop these types of glass-ceramics. The main focus of this study was the controlled development of glass-ceramics exhibiting high radiopacity in comparison to the reference glass-ceramic. This goal could be achieved with all four glass-ceramics with the preferred development of the Sr-fluoroapatite – pollucite-type glass-ceramic. In addition to this main development, it was possible to control the thermal properties. Especially the Rb-leucite containing glass-ceramic showed the highest coefficient of thermal expansion (CTE). These glass-ceramics allow optical properties, especially the translucency and color, to be tailored to the needs of biomaterials for dental applications. The authors conclude that it is possible to use twofold crystallization processes to develop glass-ceramic biomaterials featuring different properties, such as specific radiopacity values, CTEs, and optical characteristics.

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      Most cited references 16

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      Heat treatment of an MgO-CaO-SiO2-P2O5 glass gave a glass ceramic containing crystalline apatite (Ca10(PO4)6O,F2] and beta-wollastonite (CaO,SiO2) in an MgO-CaO-SiO2 glassy matrix. It showed bioactivity and a fairly high mechanical strength which decreased only slowly, even under load-bearing conditions in the body. It is used clinically as artificial vertebrae, iliac bones, etc. The bioactivity of this glass ceramic was attributed to apatite formation on its surface in the body. Dissolution of calcium and silicate ions from the glass ceramic was considered to play an important role in forming the surface apatite layer. It was shown that some new kinds of bioactive materials can be developed from CaO,SiO2-based glasses. Ceramics, metals and organic polymers coated with bone-like apatite were obtained when such materials were placed in the vicinity of a CaO,SiO2-based glass in a simulated body fluid. A bioactive bone cement which was hardened within 4 min and bonded to living bone, forming an apatite, was obtained by mixing a CaO,SiO2-based glass powder with a neutral ammonium phosphate solution. Its compressive strength reached 80 MPa comparable to that of poly(methyl methacrylate) within 3 d. A bioactive and ferromagnetic glass ceramic containing crystalline magnetite (Fe3O4) in a matrix of CaO,SiO2-based glassy and crystalline phases was obtained by a heat treatment of a Fe2O3-CaO.SiO2-B2O3-P2O5 glass. This glass ceramic was shown to be useful as thermoseeds for hyperthermia treatment of cancer.
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          The Development of Bioglass Ceramics for Medical Applications

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            Author and article information

            Affiliations
            1Research and Development, Inorganic Chemistry, Technical Fundamentals, Ivoclar Vivadent AG , Schaan, Liechtenstein
            Author notes

            Edited by: Malcolm Xing, University of Manitoba, Canada

            Reviewed by: Ashutosh Goel, Rutgers, The State University of New Jersey, USA; Piergiorgio Gentile, University of Sheffield, UK

            *Correspondence: Wolfram Höland, Research and Development, Inorganic Chemistry, Technical Fundamentals, Ivoclar Vivadent AG, Bendererstr. 2, Schaan FL 9494, Liechtenstein, wolfram.hoeland@ 123456ivoclarvivadent.com

            Dedicated to Prof. Dr. Werner Vogel, Jena, Germany, on the occasion of his 90th birthday.

            Specialty section: This article was submitted to Biomaterials, a section of the journal Frontiers in Bioengineering and Biotechnology

            Contributors
            Journal
            Front Bioeng Biotechnol
            Front Bioeng Biotechnol
            Front. Bioeng. Biotechnol.
            Frontiers in Bioengineering and Biotechnology
            Frontiers Media S.A.
            2296-4185
            13 October 2015
            2015
            : 3
            4602200 10.3389/fbioe.2015.00149
            Copyright © 2015 Höland, Schweiger, Dittmer and Ritzberger.

            This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

            Counts
            Figures: 10, Tables: 3, Equations: 2, References: 27, Pages: 11, Words: 6295
            Categories
            Bioengineering and Biotechnology
            Original Research

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