Multinuclear magnetic resonance studies of borosilicate glasses for use in glass ionomer cements: incorporation of CaO and Al2O3

Abstract

Calcium and aluminium incorporation into a sodium borosilicate glass with base composition 0.30Na₂O ∶ 0.46SiO₂ ∶ 0.24B₂O₃ was investigated. Glasses of general compositions (0.30 − x/3.3)Na₂O ∶ xCaO ∶ (0.46 − x/2.2)SiO₂ ∶ (0.24 − x/4.2)B₂O₃ (Cx) and (0.3 − x/3.3)Na₂O ∶ xAl₂O₃ ∶ (0.46 − x/2.2)SiO₂ ∶ (0.24 − x/4.2)B₂O₃ (Ax) were prepared by melt quenching. All the samples were tested for glass-ionomer cement formation. Glasses in the Cx system did not yield sustainable cements on mixing at glass to liquid ratios of 2.4 ∶ 1. The glasses of system Ax were unmixable at glass to liquid ratios between 2.4 ∶ 1 and 1.5 ∶ 1, with the exception of the sample with composition x = 0.3, which was mixable at a glass to liquid ratio of 2.4 ∶ 1, producing a cement with an average compressive strength of 69.3 MPa (σ = 6.1 MPa). ¹¹B, ²³Na, ²⁷Al and ²⁹Si magic angle spinning nuclear magnetic resonance spectroscopy was used to characterize the structure of the glass and cement samples. The results showed that the calcium boroaluminosilicate glass compositions have the potential to be used as solid components in the preparation of glass-ionomer cement formulations.