The sintering behavior, in vitro performance, and radiopacity of spark plasma sintered barium-containing calcium-phospho-alumino-borosilicate glass powders

Abstract

The effects of substituting CaO with BaO on the crystallization and sintering behavior of bioactive glass powders in the SiO2–B2O3–Al2O3–CaO–Na2O–P2O5 system were observed during the Spark Plasma Sintering (SPS) process. The outcome of thermal analysis confirmed the surface crystallization mechanism for the glasses. It was revealed that the replacement of 3.3 mol.% BaO accelerated the crystallization kinetics of glass powder while replacing 9.0 mol.% BaO prevented crystallization. The X-ray diffraction results showed that upon increasing BaO replacement, pseudo-wollastonite phase was crystalized instead of wollastonite. Additionally, by replacing 3.3 and 9.0 mol.% of BaO, the beginning temperature of the sintering process was reduced from 450 °C to 440 and 425 °C, respectively. The relative densities of the sintered bodies containing 0.0% and 3.3 mol.% of BaO were 99.95 and 99.27, respectively. Substitution of 9.0 mol.% BaO resulted in a completely amorphous and full-dense sample (relative density of 100%). The in vitro apatite formation ability and osteoblastic cell behavior of the sintered bodies were evaluated. The substitution of BaO for CaO restricted the glass apatite formation ability; however, no cytotoxic effect was found. For all SPS-sintered glasses, an appropriate cell-surface interaction was observed, confirming good cell supporting behavior of produced bodies. Moreover, the radiopacity features were assessed and the higher radiopacity was achieved for Ba-containing bodies.