Substitution of strontium for calcium in glass ionomer cements (Part 2): Effects on the cement mechanical and ion releasing properties

Abstract

Objectives: To investigate the effects of substituting strontium for calcium in fluoroaluminosilicate
glass on the mechanical and ion-releasing properties 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 - ySrF₂ – 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 then characterised by X-Ray Diffraction (XRD), particle size analysis and thermal analysis, as previously described (Part 1). 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: the compressive and bi-axial flexure strengths were tested; and, the ion release profile was studied by fluoride Ion Selective Electrode (ISE) and Inductively Coupled Plasma/Optical Emission Spectroscopy (ICP/OES).

Results: While compressive and biaxial flexural strength values did not vary significantly with strontium content, the strontium ion release from the cements increased proportionally with the increase in strontium amounts in the glass.

Conclusion: The results suggest that substitution of strontium for calcium has insignificant effects on the mechanical properties of the cement; however, strontium substitution for calcium enables the  controlled release of strontium which may have an important synergistic anti-cariogenic role with  fluoride.