Mechanical Properties and In Vitro Bioactivity of Ca 5 (PO 4 ) 2 SiO 4 Bioceramic

Abstract

Pure Ca₅(PO₄)₂SiO₄ bioceramic was first prepared by a sol–gel method using triethyl phosphate, tetraethoxysilane, and calcium nitrate tetrahydrate as original materials. Simulated body fluid (SBF) immersion tests revealed that Ca₅(PO₄)₂SiO₄ samples had a greater in vitro apatite-forming ability than hydroxyapatite (HA). After soaking Ca₅(PO₄)₂SiO₄ samples in the SBF for 1 day, bone-like apatite precipitated on the surfaces and the apatite layer became thicker with increasing the soaking time. However, few bone-like apatites precipitated on the HA samples even after soaking in the SBF for 7 days. The good in vitro bioactivity of Ca₅(PO₄)₂SiO₄ samples was attributed to the silanol (Si-OH) groups and greater solubility of Ca₅(PO₄)₂SiO₄. In addition, hot-pressed Ca₅(PO₄)₂SiO₄ ceramic exhibited lower bending strength and elastic modulus than hot-pressed HA, since the former had a lower relative density than the latter. The results have shown that Ca₅(PO₄)₂SiO₄ is a potential candidate material for bone repair.