During the recent years, many researchers have been tried to modify the chemical composition of hydroxyapatite in order to remove its defects. Dissolution rate of hydroxyapatite especially when it is used as coating on metallic sulostrate, decreases the stability of the coating in a long period of time. Therefore, the implant stabilization wouldn’t be proper. Accordingly, fibrous layer formation causes wobbling which makes second surgery inevitable. One of the other defects of hydroxyapatite is the formation of beta-tri-calcium phosphate around 1100-1200°C in coating processes such as powder plasma spray on the implant surface and also low resistance against acid environments. Hydroxyl group substitution by fluorine contributes to the formation of a new composition wich is called fluorhydroxyapatite that removes these shortcomings. The general chemical formula presented for this composition is [FHA: (Ca10 (PO4) 6 OH2-x Fx)] where x is the theoretical percentage of hydroxyl groups by fluorine ions in hydroxyapatite structure. What is more, fluorine ion increases the driving force of the reaction in deposition reactions. Having fluore ion in calcim- phosphate solution acts as a catalyst and increases the hydrolysis rate and also the formation rate of intermediate phases in order to achieve the final product. Its advantages over pure hydroxyapatite in a biological environment include: faster apatite formation (the process of biological mineralization), better absorption of proteins and osteoblasts on the surface, lower dissolution rate, higher chemical stability, improved mechanical properties, higher resistance to acidic environment, and improved cell adhesion and proliferation rates. One of the product of NikCeram Razi medical-engineering company is fluorhydroxyapatite powder with a particle size range of 50 to 70 nm. This product is prepared through both natural (extraction from animal bones) and synthetic (sol-gel) methods. In order to evaluate the characteristics of this product, XRD, SEM, TEM and In vivo and In vitro tests have been done.
