The effect of aqueous media on the mechanical properties of fluorapatite-mullite glass-ceramics.
OBJECTIVE
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.


METHODS
The glass compositions were from SiO2Al2O3P2O5CaOTiO2BaOZrO2CaF2 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.


CONCLUSIONS
Thermal changes and chemical compositions had significant effects on flexural strength and Vickers micro-hardness values.
Department of Material Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.
S
S
Mollazadeh
Department of Biomaterials, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
Siamak
S
Ajalli
Department of Biomaterials, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran. Electronic address: jafarzat@tums.ac.ir.
Tahereh S Jafarzadeh
TS
Kashi
School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran, Iran.
Bijan Eftekhai
BE
Yekta
School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran, Iran.
Jafar
J
Javadpour
School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran, Iran.
S
S
Jafari
Pareh-Tavoos Research Center, Mashhad, Iran.
Abbas
A
Youssefi
Department of Biomaterials, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
Akbar
A
Fazel
D000538:Aluminum Silicates; D001031:Apatites; D002516:Ceramics; D003764:Dental Materials; D006244:Hardness; D008422:Materials Testing
D000538:Aluminum Silicates; D001031:Apatites; D003764:Dental Materials; C049037:aluminosilicate; C025105:fluorapatite
Apatite–mullite; Dental glass–ceramics; Thermo-cycling; Vickers micro-hardness