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 of P₂O₅-CaO-Na₂O-SiO₂-TiO₂ were obtained by the sintering method. For evaluating the effect of strontium and zinc, different amounts of these elements were doped in the parent glass instead of calcium oxide. Sintering behavior of the glasses was evaluated through the measurement of bulk density, liquid absorption, and open porosity percentages. Based on the results, 600 °C was determined as the optimum sintering temperature. Based on the X-Ray diffractometry, calcium pyrophosphate was precipitated during the sintering process as the main crystallized phase. It is worth noting that changing the parent glass composition led to its phase transformation. Variation in the pH and ion concentration in the simulated body fluid as well as weight loss percentages of the samples were considered to evaluate the dissolution behavior of the samples. The in vitro tests showed that increasing the amount of strontium and zinc intensified the dissolution rate. According to scanning electron micrographs, hydroxyapatite nuclei precipitated on the surfaces of the samples after three days of simulated body fluid (SBF) soaking; but, they were dissolved in the solution after 28 days due to the dissolution of the substrate. Some residues of the grown apatite-like layer were observed on the surface of the composition when 25 and 2.5 molar percent of calcium were substituted for strontium and zinc, respectively.