Substitution of strontium for calcium in glass ionomer cements (Part 1): Glass synthesis and characterisation, and the effects on the cement handling variables and setting reaction
Objectives: To investigate the effects of substituting strontium for calcium in fluoroaluminosilicate glass on the handling variables and setting reaction of high-viscosity glass ionomer cements.
Design: An exploratory, laboratory-based study.
Setting: Dental biomaterials research laboratory, Dental Physical Sciences Unit, Barts and the London School of Medicine and Dentistry, Queen Mary, University of London.
Subjects: A series of five glasses in which strontium substitutes for calcium and based on the general formula: 4.5SiO2 - 3Al2O3 – 1.25P2O5 – xSrO - ySrF,sub>2 – zCaO - yCaF2, where x = 0, 0.5, 1.5 or 3; y = 0, 1 or 2; and, z = 0, 1.5, 2.5 or 3 were synthesized, ground, sieved and the powders characterised by X-Ray Diffraction (XRD), particle size analysis and thermal analysis. Thereafter, they were mixed with poly (acrylic acid) (PAA) and aqueous tartaric acid to form glass ionomer cements, whose properties were investigated at different time points: working and setting times were determined by rheometry; and, the setting reaction was studied by Fourier transform infra-red (FT-IR) spectroscopy.
Results: XRD confirmed the amorphous nature of the glasses, while thermal analysis showed a mixed alkaline/entropic effect on the glass transition temperature. Working and setting times did not vary significantly with strontium content but the shortest times were recorded for the cement with the smallest particle size.
Conclusion: The results suggest that substitution of strontium for calcium has insignificant effects on the manipulation and setting reaction of the cement; therefore, substitution can be optimised to produce restorative materials with beneficial anticariogenic properties.