This paper presents a study on the synthesis and characterization of hydroxyapatite that can be used to produce dental implants or serves as a replacement for other body hard tissues. The bioceramic material (hydroxyapatite) was derived from bovine bone samples after they were de-fatted and processed to produce particles measuring less than 250 μm. Processed bone powders were calcinated at 750℃ to obtain calcium phosphate compound (hydroxyapatite). This indicated complete elimination of the organic phase of the bone. The synthesized hydroxyapatite was physicochemically characterized using Fourier transform infrared spectroscopy (FTIR), an optical microscope and scanning electron microscopy (SEM). Hydroxyapatite powder was sintered into a block and then characterized mechanically by measuring its hardness using a Rockwell hardness testing machine. The hydrophilicity and hydrophobicity of the sintered blocked specimens were studied. The average wettability of the substrate, which was a characteristic of the contact angle, was found to be approximately 31.73 degrees. This contact angle value is a measure of the material hydrophilicity. The biostability/corrosive resistance of the sintered samples was simulated in vitro in phosphate buffered saline solution (pH 7.4) by incubating in an optical incubator shaker (set at 60 revolutions per minute) to mimic physiological conditions. The results showed that hydroxyapatite can be extracted economically from a natural source such as bovine bone and can be employed as a restorative biomaterial for dental implants and hard tissue replacement.
The effects of temperature on the bulk and surface properties of liquid Zn-Cd alloys have been theoretically investigated, using a combination of self association model, Darken's thermodynamic equation for diffusion, empirical model for viscosity and a statistical mechanics model. The results from this study show that change in temperature resulted in cross-over effects in bulk and surface properties. We also found that with an increase in temperature, a pronounced asymmetry of viscosity isotherm is significantly reduced, and viscosity isotherm exhibited anomalous behaviour. Our results reveal that the homocoordination tendency in Zn-Cd liquid alloys is not strong and reduces with increasing temperature. The study further suggests a pronounced segregation of Cd-atoms at the surface of Zn-Cd liquid alloys and the extent of segregation reduces with temperature. We as well found that, in addition to the reported understanding that size-factor determines the compositional location of asymmetry of the viscosity isotherm, temperature is an operating parameter that has effect, not only on the composition of asymmetry, but also on the magnitude of asymmetry. In all the properties investigated, the most pronounced effect of temperature (52.9%) is on the viscosity while the least effect (7.1%) is on the surface tension.
Titanium alloys have been extensively used in biomedical applications owing to its low density, excellent biocompatibility (i.e., biological and chemical inertness), and unique mechanical properties. However, there is a high disparity between Young's moduli of the implant and the natural bone. This disparity causes stress shielding in the body. This paper presents the effect of particle size and sintering time of Ti-6Al-4V powder used in the formation of a porous implant, sintered at 980 °C. Morphological characteristics of the sintered samples were obtained with a scanning electron microscope. The effect of surface hydrophilicity of the samples was elucidated via surface wettability testing using contact angle measurement with bio-fluid. Mechanical characterization was also evaluated with nanoindentation and a universal testing machine. The relation between Young's modulus and sintering time was presented. It was observed that the wettability decreases with sintering time and the Ti alloy powder with particle size < 150 µm had the Young's modulus that is closer to the modulus of the bone; the optimum sintering time was 5 h.
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