Papers by Author: Erdem Demirkesen

Abstract: The aim of this study is to find out the crystallization behaviour and in-vitro bioactivity character of machinable glass ceramics having different ratios of Na/K mica and apatite phases, to ascertain the best machinable composition. In order to investigate the bioactivity behavior of the samples the simulated body fluid (SBF) was prepared. Samples were removed from the solution after 1 hour, 1 day, 1, 2, 3 and 4 weeks. FEG-SEM was used to characterize the morphology of precipitation HCA layer on the surface depending on time. Molecular bonding characterization of HCA layers were carried out by using Fourier Transform Infrared Spectroscopy (FTIR) technique. The thin film X-ray diffraction (TF-XRD) analysis was used to characterize the variation of chemical composition on precipitated layer by time. Optimum results were obtained by the composition, containing 70wt% Na/K mica and 30wt% fluorapatite which had an average mica size of 3-4 microns.

Abstract: In this study; in-vitro bioactivity characterization of machinable glass-ceramics having 85 wt% sodium mica (NaMg3AlSi3O10F2) and 15 wt% fluoroapatite has been carried out. Two different heat treatment procedures are applied to the machinable glass-ceramics. The first one is nucleation at 610°C for 2 hours and crystallization at 1000°C for 3 hours and the second is nucleation at 610°C for 2 hours and crystallization at 1000°C for 4 hours. It is observed that increasing the crystallization time to 4 hours resulted in the increasing the formation of hydroxyapatite layer on surface. According to the microstructural investigations, the morphology of the precipitated crystals are different. In addition, the speed of the precipitation of hydroxyapatite is higher in glass-ceramic B than A. Thin film XRD analysis supports these results.