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Kobayashi H.Y.L.S.,Friedrich - Schiller University of Jena | Brauer D.S.,Unit of Dental Physical science | Russel C.,Friedrich - Schiller University of Jena
Materials Science and Engineering C | Year: 2010

This paper reports on the mechanical properties and pH upon degradation of phosphate glass fibre reinforced methacrylate-modified oligolactide. Phosphate glass fibres of the composition 51.04 P 2O 5-21.42 CaO-25.51 Na 2O-2.03 SiO 2 (mol%) were produced by a crucible spinning technique. Fibres were embedded into a matrix of a degradable organic polymer network based on methacrylate-modified oligolactide; samples with and without addition of CaCO 3 for pH control were produced. pH during degradation in physiological NaCl solution could be increased to up to 6.5 by addition of 20 wt.% calcium carbonate to the fibre composites. pH in Tris buffer solution was about 7.11. Mechanical properties of dry specimens were investigated during 3-point bending tests and gave elastic moduli in the range of cortical bone (15 to 20 GPa). However, addition of calcium carbonate decreased tensile strength of the fibre composites and resulted in brittle fracture behaviour, while CaCO 3-free composites showed a fibrous fracture mode. Control of pH and degradation is a requirement for obtaining a fracture fixation device with degradation properties matching in vivo requirements. Results show that addition of CaCO 3 is suitable for controlling the pH during degradation of metaphosphate glass polymer composites. © 2010 Elsevier B.V. All rights reserved. Source


Mneimne M.,Unit of Dental Physical science | Hill R.G.,Unit of Dental Physical science | Bushby A.J.,Queen Mary, University of London | Brauer D.S.,Unit of Dental Physical science
Acta Biomaterialia | Year: 2011

Bioactive glass-containing toothpastes for treating dentine hypersensitivity work by precipitating hydroxycarbonate apatite (HCA) onto the tooth surface, but concerns exist over the long-term durability of HCA in the mouth. Fluoride-containing bioactive glasses form fluorapatite (FAp) in physiological solutions, which is more chemically stable against acid attack. The influence of phosphate content on apatite formation was investigated by producing a low-phosphate (about 1 mol% P 2O 5) and a high-phosphate (about 6 mol%) series of melt-derived bioactive glasses in the system SiO 2P 2O 5CaONa 2O; increasing amounts of CaF 2 were added by keeping the ratio of all other components constant. pH change, ion release and apatite formation during immersion in Tris buffer at 37 °C over up to 7 days were investigated. Crystal phases formed in Tris buffer were characterized using infrared spectroscopy, X-ray diffraction and solid-state nuclear magnetic resonance (NMR) spectroscopy. An increase in phosphate or fluoride content allowed for apatite formation at lower pH; fluoride enhanced apatite formation due to lower solubility of FAp compared to hydroxyapatite or HCA. High phosphate content glasses formed apatite significantly faster (within 6 h) than low phosphate content glasses (within 3 days). In addition, an increase in phosphate content favoured apatite formation rather than fluorite (CaF 2). 19F magic angle spinning NMR showed the apatite formed by fluoride-containing glasses to be FAp, which makes these glasses of particular interest for dental applications. This study shows that by varying the phosphate content, the reactivity and apatite formation of bioactive glasses can be controlled successfully. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source

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