Effect of gamma radiation on properties of a calcium phosphate-calcium sulfate composite cement

The present study investigates γ-radiation effect on structure and selected properties of a tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA)/calcium sulfate hemihydrate (CSH) cement immersed in Hanks' solution. The results indicate that, at a dosage of 25 kGy, the working and setting times of the cement paste derived from γ-ray-sterilized TTCP/DCPA/CSH powder did not change significantly. At 50 kGy or higher, however, both significantly decreased. A dose of 25 kGy caused the 1-d compressive strength of the cement to decrease by 15%. Further increases in γ-ray dose did not further change the strength. After immersion for 1 day, the pH values of all non-sterilized and sterilized samples were in the range of 7.68.0. The XRD patterns of non-sterilized and sterilized powders were substantially similar. After immersion for 1 day, TTCP phase was still distinguishable, while CSH peaks were largely diminished and apatite phase became dominant. The non-sterilized sample had a significantly higher apatite conversion ratio than those of γ-ray-sterilized samples. The average 1-d porosity values of all sterilized and non-sterilized samples were similar (3133%). The γ-ray-sterilized cement samples had coralline type morphology with numerous tiny apatite crystals and micropores. Compared to the sterilized samples, the non-sterilized cement showed a smoother and denser morphology.