Silicon-stabilized α-tricalcium phosphate and its use in a calcium phosphate cement: Characterization and cell response

alpha-Tricalcium phosphate (alpha-TCP) is widely used as a reactant in calcium phosphate cements. This work aims at doping alpha-TCP with silicon with a twofold objective. On the one hand, to study the effect of Si addition on the stability and reactivity of this polymorph. On the other, to develop Si-doped cements and to evaluate the effect of Si on their in vitro cell response. For this purpose a calcium-deficient hydroxyapatite was sintered at 1250 degrees C with different amounts of silicon oxide. The high temperature polymorph alpha-TCP was stabilized by the presence of silicon, which inhibited reversion of the beta -> alpha transformation, whereas in the Si-free sample alpha-TCP completely reverted to the beta-polymorph. However, the beta-alpha transformation temperature was not affected by the presence of Si. Si-alpha-TCP and its Si-free counterpart were used as reactants for a calcium phosphate cement. While Si-alpha-TCP showed faster hydrolysis to calcium-deficient hydroxyapatite, upon complete reaction the crystalline phases, morphology and mechanical properties of both cements were similar. An in vitro cell culture study, in which osteoblast-like cells were exposed to the ions released by both materials, showed a delay in cell proliferation in both cases and stimulation of cell differentiation, more marked for the Si-containing cement. These results can be attributed to strong modification of the ionic concentrations in the culture medium by both materials. Cadepletion from the medium was observed for both cements, whereas continuous Si release was detected for the Si-containing cement. (c) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.