zeolites and fluorapatite

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.. 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).. 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.. Thermal changes and chemical compositions had significant effects on flexural strength and Vickers micro-hardness values.

Topics: Aluminum Silicates; Apatites; Ceramics; Dental Materials; Hardness; Materials Testing

The biological performance of a porous apatite-mullite glass-ceramic, manufactured via a selective laser sintering (SLS) method, was evaluated to determine its potential as a bone replacement material. Direct contact and extract assays were used to assess the cytotoxicity of the material. A pilot animal study, implanting the material into rabbit tibiae for 4 weeks, was also carried out to assess in vivo bioactivity. The material produced by SLS did not show any acute cytotoxic effects by either contact or extract methods. There was no evidence of an apatite layer forming on the surface of the material when soaked in SBF for 30 days, suggesting that the material was unlikely to exhibit bioactive behaviour in vivo. It is hypothesized that the material was unable to form an apatite layer in SBF due to the fact that this glass-ceramic was highly crystalline and the fluorapatite crystal phase was relatively stable in SBF, as were the two aluminosilicate crystal phases. There was thus no release of calcium and phosphorus and no formation of silanol groups to trigger apatite deposition from solution within the test time period. Following implantation in rabbit tibiae for 4 weeks, bone was seen to have grown into the porous structure of the laser-sintered parts, and appeared to be very close to, or directly contacting, the material surface. This result may reflect the local environment in vivo compared to that artificially found with the in vitro SBF test and, furthermore, confirms previous in vivo data on these glass-ceramics.

Topics: Aluminum Silicates; Animals; Apatites; Biocompatible Materials; Body Fluids; Bone Substitutes; Ceramics; Glass; Lasers; Materials Testing; Microscopy, Electron, Scanning; Rabbits; Tibia; Tomography, X-Ray Computed

A number of bioactive ceramics have been researched since the development of Bioglass in the 1970's. Fluorapatite mullite has been developed from the dental glass-ceramics used for more general hard tissue replacement. Being brittle in nature, glass-ceramics are currently used mainly as coatings. This paper shows that fluorapatite glass LG112 can be used as a sputtered glass coating on roughened surfaces of Ti6Al4V for possible future use for medical implants. An AFM was used to measure the roughness of the surface before and after coating to determine the change in the topography due to the coating process as this greatly affects cell attachment. The sputter coating partially filled in the artificially roughened surface, changing the prepared topography. Osteoblasts have been successfully grown on the surface of these coatings, showing biocompatibility with bone tissue and therefore potential use in hard tissue repair.

Topics: Alloys; Aluminum Silicates; Apatites; Biomedical Engineering; Bone Substitutes; Cell Line; Cell Proliferation; Cell Survival; Coated Materials, Biocompatible; Humans; Materials Testing; Osteoblasts; Surface Properties; Titanium

This study investigated a series of ionomer glasses based on the formula: 4.5SiO(2)-1.5P(2)O(5-)(X)Al(2)O(3)-4.5CaO-0.5CaF(2), where X was varied from 3.0 to 1.5. The possibility of processing ionomer glasses using a heat-pressing method for dental restorations was investigated.. A simple flow test was designed to measure the amount of flow the glasses underwent as a result of heat-pressing at 1150 degrees C for different times. Heat-pressed samples of the X=3.0, 2.8, 2.4 and 2.0 glass were further heat-treated for 1 and 4 h at 1150, 1200 and 1250 degrees C to promote crystal growth. Scanning electron microscopy was used to investigate the microstructure of the glass-ceramics. X-ray diffraction was used to identify the crystalline phases in the glass-ceramics.. The ionomer glasses exhibited excellent flow ability. Crystallization could not be suppressed during heat-pressing. Very fine scale fluorapatite crystals were present in all of the samples after heat-pressing. Mullite and/or anorthite formed as a second crystal phase. On further heat-treatment of the samples, changes in crystal phases took place.. Apatite was the main crystalline phase produced in the glass-ceramics; this factor is of clinical significance. In conclusion these glass-ceramics could be suitable for all-ceramic dental restorations.

Topics: Acrylic Resins; Aluminum Silicates; Apatites; Calorimetry, Differential Scanning; Ceramics; Crystallization; Crystallography, X-Ray; Dental Porcelain; Dental Restoration, Permanent; Hot Temperature; Microscopy, Electron, Scanning; Rheology; Silicon Dioxide; Viscosity