The effects of adding Nb2O5 on the physical properties and glass structure of two glass series derived from the 45S5 Bioglass((R)) have been studied. The multinuclear Si-29, P-31, and Na-23 solid-state MAS NMR spectra of the glasses, Raman spectroscopy and the determination of some physical properties have generated insight into the structure of the glasses. The Si-29 MAS NMR spectra suggest that Nb5+ ions create cross-links between several oxygen sites, breaking Si-O-Si bonds to form a range of polyhedra [Nb(OM)(6-y)(OSi)(y)], where 1y5 and M=Na, Ca, or P. The Raman spectra show that the Nb-O-P bonds would occur in the terminal sites. Adding Nb2O5 significantly increases the density and the stability against devitrification, as indicated by T(T-x-T-g). Bioglass particle dispersions prepared by incorporating up to 1.3mol% Nb2O5 by replacing P2O5 or up to 1.0mol% Nb2O5 by replacing SiO2 in 45S5 Bioglass((R)) using deionized water or solutions buffered with HEPES showed a significant increase in the pH during the early steps of the reaction, compared using the rate and magnitude during the earliest stages of BG45S5 dissolution.