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Mollazadeh S.,Iran University of Science and Technology | Eftekhari Yekta B.,Iran University of Science and Technology | Javadpour J.,Iran University of Science and Technology | Yusefi A.,Pareh Tavoos Research Center | Jafarzadeh T.S.,Tehran University of Medical Sciences
Journal of Non-Crystalline Solids | Year: 2013

The effect of TiO2, ZrO2, BaO and extra addition of silica on the crystallization behavior, microstructure and mechanical properties of an apatite-mullite based glass-ceramic system were investigated by means of X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The precipitated crystalline phases were fluorapatite [Ca10(PO 4)6F2] and mullite [Al6Si 2O13], which apart from the extra bearing SiO2 specimen were rod-like in the other specimens. The rod-like crystalline phases' lengths were small, i.e. < 20 μm, in the TiO2 and BaO containing glass-ceramics, but small addition of ZrO2 enhanced the length of crystalline phases to approximately 50 μm. The flexural strength and fracture toughness of the prepared glasses and glass-ceramics were also studied. The results showed that the additive oxides affected both parameters differently. The highest fracture strength and fracture toughness values belonged to the TiO2 and BaO containing glass-ceramics which contained smaller crystal size. The mechanical properties of the prepared glass-ceramic samples did not differ strongly and/or were even decreased by addition of ZrO2 and extra amount of SiO2. © 2012 Elsevier B.V. Source


Mollazadeh S.,Ferdowsi University of Mashhad | Ajalli S.,University of Tehran | Kashi T.S.J.,University of Tehran | Yekta B.E.,Iran University of Science and Technology | And 4 more authors.
Dental Materials | Year: 2015

Objectives To verify the effects of alternating thermal changes in aqueous media and chemical composition on mechanical properties of apatite-mullite glass-ceramics and to investigate concentration of ions eluted from glass-ceramics in aqueous media. Materials and methods The glass compositions were from SiO2-Al2O3-P2O5-CaO-TiO2-BaO-ZrO2-CaF2 system. Glass-ceramics were prepared by heat-treating at 1100°C for 3 h samples alternately immersed in water at 5 and 60°C. The 3-point bending strength (n = 10) were determined using 3 × 4 × 25 mm/bar and a universal testing machine, at a cross-head speed of 0.1 mm/min. Vickers micro hardness were evaluated by applying a total of 15-20 indentations under a 100 g load for 30 s. Concentrations of ions eluted from glass-ceramics immersed in 60 ± 5°C double distilled water were determined by ion chromatography. The toxicity of glass-ceramics was assessed by seeding the osteosarcoma cells (MG63) on powder for different days and their cell proliferation assessment was investigated by MTT assay. The data were analyzed using one way analysis of variance and the means were compared by Tukey's test (5% significance level). Results The highest flexural strength and hardness values after thermal changes belonged to TiO2 and ZrO2 containing glass-ceramics which contained lower amount of released ions. BaO containing glass-ceramic and sample with extra amount of silica showed the highest amount of reduction in their mechanical strength values. These additives enhanced the concentration of eluted ions in aqueous media. MTT results showed that glass-ceramics were almost equivalent concerning their in-vitro biological behavior. Significance Thermal changes and chemical compositions had significant effects on flexural strength and Vickers micro-hardness values. © 2015 Academy of Dental Materials. Source


Mollazadeh S.,Ferdowsi University of Mashhad | Ajalli S.,Tehran University of Medical Sciences | Kashi T.S.J.,Tehran University of Medical Sciences | Yekta B.E.,Iran University of Science and Technology | And 4 more authors.
Dental Materials | Year: 2015

Objectives: To verify the effects of alternating thermal changes in aqueous media and chemical composition on mechanical properties of apatite-mullite glass-ceramics and to investigate concentration of ions eluted from glass-ceramics in aqueous media. Materials and methods: The glass compositions were from SiO2 Al2O3 P2O5 CaOTiO2 BaOZrO2 CaF2 system. Glass-ceramics were prepared by heat-treating at 1100°C for 3h samples alternately immersed in water at 5 and 60°C. The 3-point bending strength (n =10) were determined using 3×4×25mm/bar and a universal testing machine, at a cross-head speed of 0.1mm/min. Vickers micro hardness were evaluated by applying a total of 15-20 indentations under a 100g load for 30s. Concentrations of ions eluted from glass-ceramics immersed in 60±5°C double distilled water were determined by ion chromatography. The toxicity of glass-ceramics was assessed by seeding the osteosarcoma cells (MG63) on powder for different days and their cell proliferation assessment was investigated by MTT assay. The data were analyzed using one way analysis of variance and the means were compared by Tukey's test (5% significance level). Results: The highest flexural strength and hardness values after thermal changes belonged to TiO2 and ZrO2 containing glass-ceramics which contained lower amount of released ions. BaO containing glass-ceramic and sample with extra amount of silica showed the highest amount of reduction in their mechanical strength values. These additives enhanced the concentration of eluted ions in aqueous media. MTT results showed that glass-ceramics were almost equivalent concerning their in-vitro biological behavior. Significance: Thermal changes and chemical compositions had significant effects on flexural strength and Vickers micro-hardness values. © 2015 Academy of Dental Materials. Source

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