Prospecting potential nucleating agents for Biosilicate® parent glass

Abstract

Biosilicate^® is a strong, highly bioactive, bactericidal, machinable, (almost) fully crystalline glass–ceramic that has been successfully used in several in vivo and clinical trials. However, there is still scope to optimize its crystallization ability, resulting microstructure and properties. Here we tested 13 compounds, from which we choose six for more detailed screening (2% ZrO₂, 6% Fe₂O₃, 3% WO₃, 4% NaF, 3 and 20% TiO₂, 2, 4 and 8% Li₂O, and 4% TiO2 + 3% ZrO2, in wt.%) as potential nucleating agents. We used DSC analyses to estimate their tendency to boost internal nucleation. For some compositions, we also used optical microscopy. XRD was used to evaluate the crystalline phase, most of these modified BIOS glasses showed combeite as the main phase. To evaluate whether one of the key components of the formula, P₂O₅, significantly affects the nucleation process, a particular composition (25.97Na₂O-24.23CaO-49.8SiO₂, wt.%), named SS, had its P₂O₅ content replaced by Li₂O and Fe₂O₃. Among the additives tested, Li₂O significantly increased the internal nucleation rate. This study confirmed that DSC is a practical, fast tool to assess the suitability of prospective nucleating agents, and revealed a new, unexpected, nucleating agent (Li₂O) for this bioactive glass family.