Influence of Ionic Substitution on the Mechanical Properties of Nanosized Biphasic Calcium Phosphates

Synthetic hydroxyapatite ceramics have been used for bone repair, implants coating and as fillers. However, hydroxyapatite ceramics have low resorption rate. In order to increase resorption rate, researchers suggested that adding another calcium phosphates phase would overcome this problem. Combining β-tricalcium phophates (β-TCP) with hydroxyapatite (HA) would increase resorption rate without compromising other properties. The mixture containing β-TCP with HA is known as biphasic calcium phosphates (BCP) ceramics and existed at various ratios depending on processing conditions. BCP is obtained by heating calcium apatite at temperature above 750 °C. Calcium apatite is influenced by preparation synthesis particularly on reaction temperature and reaction pH. The ratio of HA/β-TCP is depending on calcium phosphates ratio of synthesized apatite and heat treatment temperature. Biphasic calcium phosphate ceramic have been used as biomaterial in bone defects reconstruction applications. Furthermore, recent advancements in nanotechnology have increase investigation on nanosized BCP. By producing nanosized BCP, the material properties could be improved particularly in mechanical properties. It is known that micrometer sized calcium phosphates have poor mechanical properties. Thus cannot be used in load bearing applications. It is suggested that by reducing particles size into nanometer, better properties of calcium phosphates can be obtained particularly in sinterability, biocompatibility and mechanical properties. Furthermore, these properties can be altered by substituting various ions. In this review, the synthesis methods and characteristics of calcium phosphates were studied. Numerous properties of calcium phosphates are improved compared to micro meter sized structured by doping with various ions. Moreover, mechanical properties and phase stability of ion doped calcium phosphates after heat treatment should be investigated in more detail.