Effect of heat treatment on bioactivity and mechanical properties of PDMS-modified CaO-SiO2-TiO2 hybrids via sol-gel process

Crack- and pore-free transparent monolithic disks of polydimethylsiloxane (PDMS)- modified CaO-SiO2-TiO2 hybrids were obtained by hydrolysis and polycondensation of PDMS, tetraethoxysilane, tetraisopropyltitanate and calcium nitrate. The product as-dried at 60 degreesC formed an apatite on its surface in a simulated body fluid (SBF) within only one day, indicating its high bioactivity. The apatite-forming ability decreased slightly by a heat treatment below 250 degreesC. The bending strength of the product was about 11 MPa, independent of the heat treatment. This average strength value is comparable to that of the human cancellous bone. Young's modulus of the products increased from 100 to 500 MPa with increasing heat treatment temperature from 60 to 250 degreesC, but its values were within the range of those of the human cancellous bone. The strain at failure of the products decreased with increasing heat treatment temperature. Failure strains went down to the magnitudes exhibited by the human cancellous bone, when the products were heat treated in the temperature range from 150 to 250 degreesC. Thus, highly bioactive hybrids with mechanical properties analogous to those of the human cancellous bone were obtained. This new kind of bioactive hybrid may be useful as a bone-repairing material. (C) 2001 Kluwer Academic Publishers.