P-Containing ORMOSILS for bone reconstruction

PDMS–CaO–SiO₂–phosphatoethylsilane (PES) ORMOSILS with different P content were prepared as monoliths. The use of a phosphorous source such as diethyl phosphatoethyl triethoxysilane (DEPETES) allowed the introduction at a molecular level of P into an ORMOSIL network. The effect of the amount of P on the in vitro bioactivity of these sol–gel derived ORMOSILS (denoted as Type A) was studied. The in vitro bioactivity of these new ORMOSILS was evaluated by soaking them in a simulated body fluid (SBF) and characterising the new calcium phosphate layer formed over the monolith surfaces. In an attempt to increase the homogeneity of the organic content throughout the hybrid network, the precursor monomer of PDMS (dimethyl diethoxysilane [DDS]) has been used to produce the polymerisation in situ. This polymerisation took place at the same time as that of the hydrolysis and condensation of TEOS and the calcium source. The in vitro bioactivity of these P-free materials in SBF was investigated. The DDS content required to produce monoliths that form a calcium phosphate layer over their surface when soaked in SBF was found to be between 0.5 and 1.5 (DDS:TEOS in molar ratio). Larger amounts of DDS led to phase separation and non-bioactive materials.