Synthesis of Glasses and Glass-Ceramics of the System Diopside - Fluorapatite and Characterization of Their in Vitro Bio
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.81
Synthesis of Glasses and Glass-Ceramics of the System Diopside - Fluorapatite and Characterization of Their in Vitro Bioactivity Jorge López-Cuevas*, Juan C. Rendón-Angeles, José L. Rodríguez-Galicia and Carlos A. Gutiérrez-Chavarría CINVESTAV-IPN, Unidad Saltillo, Calle Industria Metalúrgica No. 1062, Parque Industrial Saltillo Ramos Arizpe, Ramos Arizpe, Coahuila, México, CP 25900
*Corresponding author; Tel. +52 844 4389600; E-mail address: [email protected]
Abstract
Glasses and glass-ceramics of the system Diopside [D, CaMgSi2O6] - Fluorapatite [FAp, Ca5(PO4)3F] were synthesized and characterized. The studied theoretical phase compositions were (wt%): 1) 70% D-30% FAp, 2) 60% D-40% FAp and 3) 80% D-20% FAp. The glassceramics were synthesized by isothermal treatment of the corresponding parent glasses at either 800, 900 or 1000 ºC, with holding times of either 30 min, 2 h or 5 h at high temperature. The in vitro bioactivities of all materials were tested in Kokubo’s Simulated Body Fluid (SBF), for 21 days at pH = 7.4 and 37 ºC. All materials were characterized by XRay Diffraction (XRD) and Scanning Electron Microscopy (SEM/EDS). In all cases, the in vitro bioactivity increased with decreasing crystallization degree in the materials, which was likely due to an inhibitory effect of the structural changes occurring during thermal treatment of the glasses. This was more accentuated for long thermal treatments. After 21 days of soaking in the SBF, an apatite-like surface layer, with a Ca/P molar ratio close to 1.67, was formed in the case of the parent glass of composition 2. This was attributed to an enhancing effect of so-called “phase separation” phenomenon that took place during the synthesis of that particular glass. Lastly, the MgO content of the glasses made no clear difference on their in vitro bioactivity.
INTRODUCTION The Diopside [D, CaMgSi2O6] - Fluorapatite [FAp, Ca5(PO4)3F] system can provide fundamental knowledge for the development of new glass-ceramic biomaterials having an attractive combination of high mechanical strength, good chemical resistance and good biocompatibility [1,2]. FAp belongs to the pyroxene mineral family and it is bioactive and possesses the ability to bond to bone. On the other hand, the D phase is also bioactive, has a high strength and it can act as a source of magnesium ions inside the
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human body. It is known [3] that magnesium plays an important role in biochemical and physiological functions of the human body and that a lack of it may be associated with cardiovascular and osseous diseases. It is also known [4] that magnesium plays an important role regarding the formation and evolution of a surface apatite-like layer in bioglasses soaked in Simulated Body
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