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

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.