الفهرس 
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Abstract
Purpose of the research: This work aims to study the structural properties of calcium phosphate in the form of hydroxyapatite, beta-tri-calcium phosphate, and biphasic-calcium phosphate and to clarify the role of silver in the bactericidal effect and the bioactivity. Materials and methods used: Five compounds of silver-hydroxyapatite composites were prepared by solution method using the formula Ca10-x (PO4)6(OH)2 where x=0, 0.4, 0.8, 1.2, and1.6 mole and to study the structural changes, calcium phosphates composites were sintered at 700, 800, 900, and 1000 °C for 1, 4, and 8 hour. It was also studied along with the structural changes the antibacterial effect and the biological activity of the composites substituted with silver and without silver. Summary and Conclusions: In this study, the effect of replacing calcium with silver in calcium phosphate compounds (hydroxyapatite), beta-tri-calcium phosphate, and biphasic calcium phosphate was investigated. The results showed that silver ions have multiple properties as a nucleation agent, as they affected and accelerated the formation of hydroxyapatite, beta-tri-calcium phosphate, and biphasic calcium phosphate. Hydroxyapatite was prepared by solution method. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) of the prepared sample containing 0.4 mol of hydroxyapatite were used to study the thermal behavior of the sample. The structural changes resulting from the sintering process as a function of temperature and sintering time were also studied using thermal infrared spectroscopy and X-ray diffraction techniques. The degree of crystallinity was calculated where it was found that the degree of crystallinity decreases if the sintering temperature is raised for one hour, and increases with the increase in the sintering time. It was also found that the degree of crystallinity decreases upon substitution with low content of silver and increases with high content of silver. The selected composites were analyzed using scanning electron microscope and transmission electron microscope, and it was found that all samples contain polycrystalline diffraction patterns, whether they are arranged regularly or randomly. To study the effect of silver on the antibacterial properties of calcium phosphate compounds, the diameter of the inhibition zone was measured. It was found that the antibacterial effect increases linearly for all the compounds substituted with high contents of silver. To test the bioactivity of the prepared samples, the compounds were immersed in simulated body fluid (SBF), and their absorbability was studied. After immersion, morphological and structural changes were characterized by using the techniques of thermal infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. The hydroxyapatite, beta-tri-calcium phosphate, and biphasic calcium phosphate composites showed reduction in crystallinity which means phase dissolution and precipitation of hydroxyapatite as a result of increased osseous bonding, thus becoming a bio-ceramic with surface-active properties for use in bone binding. The phases of amorphous β-Tri-Calcium Phosphate and Biphasic Calcium Phosphate showed increased crystallization, which means phase stability and hydroxyapatite precipitation, thus becoming a bio-ceramic with surface-active properties and stimulating bone growth for use in bone formation as biodegradable scaffolds. The low content of silver improves the bioactivity as a nucleating agent for the formation of hydroxyapatite while the high content prevents the formation of hydroxyapatite which means that the bioactivity is reduced.