Effect of sterilization on the properties of CDHA-OCP-beta-TCP biomaterial

The effect of the method of sterilisation on the physical, chemical and mechanical properties of a new bone repair material was studied. The material was obtained by thermal hydrolysis of beta-tricalcium phosphate/orthophosphoric acid cement and was composed of calcium-deficient hydroxyapatite, octacalcium phosphate (OCP), and beta-tricalcium phosphate. Partial decomposition of the OCP was observed after sterilisation by the three methods. Decomposition increased in the following sequence of methods: ethylene oxide; autoclaving; dry oven. Mechanical strength decreased with regard to non sterilised material in the sterilisation sequence: ethylene oxide; dry oven; autoclaving. The compressive strength was 8.5 plus or minus 1.0; 9.0 plus or minus 1.2; 8.2 plus or minus 0.8 and 6.5 plus or minus 1.0 MPa, whereas diametral tensile strength was 2.1 plus or minus 0.3; 2.5 plus or minus 0.1; 1.9 plus or minus 0.9 and 1.6 plus or minus 0.3 for the material sterilised by ethylene oxide, dry oven, and autoclaving, respectively. Several compositional and microstructural changes were detected after dry heat and autoclave sterilisation. Ethylene oxide sterilisation had lesser effect on the chemical composition and strength than dry heat and autoclaving. 26 refs.