Structural Characteristics of a Family of Bioactive Glasses Formed by Replacing Varying Amounts of SiO ₂ in 45S5 Glass with B ₂O ₃

Abstract

Bioactive glasses with controllable reactivity and bioactive potential have been created by replacing varying amounts of SiO₂in silicate 45S5 glass with B₂O₃. While these borate and borosilicate glasses formed from 45S5 glass are receiving growing interest for hard and soft tissue repair, their structural characteristics have received little attention. In this study, the structural characteristics of a family of bioactive glasses formed by replacing varying amounts of SiO₂ in 45S5 glass with B₂O₃ were evaluated using multiple spectroscopic techniques. A benefit of this work is the use of multiple spectroscopic techniques and one set of compositional variation for a widely used family of bioactive glasses. The results showed that when compared to 45S5 glass, SiO₂ remained the primary network in a borosilicate glass designated 45S5-1B, formed by replacing 33.3 mol. % of the SiO₂ in 45S5 with B₂O₃. The glass network in both glasses was composed mainly of SiO₄ tetrahedral units with 2 nonbridging oxygen atoms. In comparison, B₂O₃ was the primary network former in borosilicate 45S5-2B and borate 45S5-3B glasses, formed by substituting 66.7 mol. % and 100 mol. %, respectively, of SiO₂ in 45S5 glass with B₂O₃. The network in these two glasses was composed mainly of trigonal BO₃ structural units (orthoborate or pyroborate groups) and a smaller fraction ∼30%) of tetrahedral BO₄ units. The observed structural characteristics are used to rationalize data from a previous study for the reactivity and bioactive potential of this family of bioactive glasses.

Keywords: Bioactive glass, glass structure, silicate glass, borate glass, borosilicate glass