Influence of P<sub>2</sub>O<sub>5</sub> Content on In Vitro Behavior of CaO-ZnO-P<sub>2</sub>O<sub>5</sub> Bioglass Powder Compacts

Abstract

CaO-ZnO-P2O5 bioglasses were synthesized in order to study the relationship between their composition and in vitro behavior. We specifically examined the relationship between the P2O5 content and the in vitro behavior of the powder compacts. The weight gain percentage after immersion in a simulated body fluid (SBF) for a 4-week-period increased with the increase in P2O5 content up to a certain threshold, and the maximum weight gain was observed when the P2O5 content was 33.6 mol%. As the amount of P2O5 increased further, the weight gain in the samples rapidly turned to a negative value. In other words, it was found that there was a threshold for the P2O5 content. In the sample that had the maximum weight gain, submicron level, round precipitates were observed after the SBF test and presumed to be an amorphous calcium-zinc phosphate substance. Furthermore, a phosphate glass structure that promotes the precipitation of the above substances was proposed. The structure was formed when the long-chain structure of P-O (Q2 group), which promotes the dissolution of the P component, and the short-chain structure of P-O (Q0 and Q1 groups), which are considered to be the starting points of precipitation, coexist in a well-balanced ratio within the glass.