SILICON-SUBSTITUTED HYDROXYAPATITE SYNTHESIZED BY A HYDROTHERMAL METHOD

Silicon-substituted hydroxyapatite (Si-HA) bioceramics are widely used as bone replacement materials. The incorporation of silicone into hydroxyapatite (HA) has been shown to increase the rate of bone apposition into HA bioceramics implants significantly. Si, an essential trace element required for healthy bone and connective tissues, influences the biological activity of CaP (calcium phosphate) materials by modifying material properties and it has direct effects on the physiological processes in skeletal tissue. Silicon has been substituted in the HA lattice by replacing some of the phosphate (PO4) groups by silicate (SiO4) groups resulting in silicate substituted HA described as Ca-10(PO4)(6-x)(SiO4)\(OH)(2-x). Si-HA was prepared successfully by hydrothermal method, using Ca(NO3)(2), (NH4)(3)PO4 and Si(OCH2CH3)(4) TEOS as starting materials. The analysis of samples by ICP, XRD, FTIR and SEM showed that the substitution of phosphate groups by silicate groups causes some OH- loss to maintain the charge balance and changes of the lattice parameters were observed. Furthermore the substitution of the silicate groups reduces the size of Si-HA crystallites.