Synthesis and in vitro bioactivity of dicalcium silicate powders

In the present investigation, beta-dicalcium silicate (beta-Ca2SiO4) and gamma-dicalcium silicate (gamma-Ca2SiO4) powders were synthesized by sol-gel process and hydrothermal synthesis, respectively. The in vitro bioactivity of both beta-, and gamma-Ca2SiO4 was investigated by soaking the powders in simulated body fluid (SBF) for various time periods to analyze the nucleation and growth of hydroxyapatite (HAp) on the surface of the powders. After soaked in SBF for 6 h, HAp appeared on the surface of beta-, and gamma-Ca2SiO4 particles, and uniform lathlike aggregates with typical morphology of HAp crystals formed after 5 days. The beta-Ca2SiO4 showed strong hydration when soaked in SBF and the hydration was favorable for formation of carbonate-containing hydroxyapatite on the surface of the materials. The gamma-Ca2SiO4 was not hydrated in SBF solution and showed a slower formation of carbonate-containing hydroxyapatite on the surface when compared with beta-Ca2SiO4. In addition, the Si concentration in the SBF increased quickly up to 5 days and remained invariable with increased soaking time. The results obtained indicate that hydroxyapatite nuclei can form and grow on the beta-, and gamma-Ca2SiO4 particles, and these two dicalcium silicates are potential candidates as biomaterials for hard tissue repair. (C) 2003 Elsevier Ltd. All rights reserved.