Effect of SrO and ZnO on Densification and in Vitro Behaviors of P2O5-CaO-Na2O-SiO2-TiO2 Bioactive Glass-Ceramics

Abstract

Phosphate-based glass ceramics in the system P₂O₅-CaO-Na₂O-SiO₂-TiO₂ were obtained by the sintering method. To evaluate the effect of strontium and zinc, different amounts of these elements were doped into the parent glass in place of calcium oxide. The sintering behavior of the glasses was evaluated through measurements of bulk density, liquid absorption, and open porosity percentages. Based on the results, 600 °C was determined as the optimum sintering temperature. X-ray diffractometry revealed that calcium pyrophosphate precipitated during the sintering process as the main crystalline phase. It is worth noting that changing the parent glass composition led to a phase transformation. Variations in pH and ion concentration in simulated body fluid (SBF), as well as weight loss percentages of the samples, were used to evaluate their dissolution behavior. The in vitro tests showed that increasing the amounts of strontium and zinc accelerated the dissolution rate. According to scanning electron micrographs, hydroxyapatite nuclei precipitated on the surfaces of the samples after three days of SBF soaking; however, they dissolved into the solution after 28 days due to substrate dissolution. Residues of the grown apatite-like layer were observed on the surface of the composition when 25 mol% and 2.5 mol% of calcium were substituted with strontium and zinc, respectively.