The influence of particle size and fluorine content of aluminosilicate glass on the glass ionomer cement properties

ObjectiveGlass ionomer cements (GIC) are clinically accepted dental restorative materials mainly due to their direct chemical adhesion to both enamel and dentin and their ability to release fluoride. However, their mechanical properties are inferior compared to those of amalgam and composite. The aim of this study is to investigate if combinations of nano- and macrogranular glass with different compositions in a glass ionomer cement can improve the mechanical and physical properties.MethodsGlasses with the composition 4.5 SiO2–3 Al2O3–1.5 P2O5–(5 − x) CaO − x CaF2 (x = 0 and x = 2) were prepared. Of each type of glass, particles with a median size of about 0.73 μm and 6.02 μm were made.ResultsThe results show that the setting time of GIC decreases when macrogranular glass particles are replaced by nanogranular glass particles, whereas the compressive strength and Young's modulus, measured after 24 h setting, increase. The effects are more pronounced when the nanogranular glass particles contain fluoride. After thermocycling, compressive strength decreases for nearly all formulations, the effect being most pronounced for cements containing nanogranular glass particles. Hence, the strength of the GIC seems mainly determined by the macrogranular glass particles.Cumulative F−-release decreases when the macrogranular glass particles with fluoride are replaced by nanogranular glass particles with(out) fluoride.SignificanceThe present study thus shows that replacing macro- by nanogranular glass particles with different compositions can lead to cements with approximately the same physical properties (e.g. setting time, consistency), but with different physicochemical (e.g. F−-release, water-uptake) and initial mechanical properties. On the long term, the mechanical properties are mainly determined by the macrogranular glass particles.