IADR Abstract Archives
Effects of Powder Particle Size on Characteristics of Glass-ionomer Cement
Objectives: Glass-ionomer cement (GIC) is known as caries-preventive material. Although having various clinical applications, GIC for filling is less translucent than restorative composite resins. This study aimed to investigate effects of novel FASG’s (powder) particle size on GIC’s translucency and material properties, and evaluate various properties of a novel GIC (developed based on the investigation results) for filling, in comparison with commercially-available products.
Methods: A novel FASG was milled to obtain experimental powders (refer to the table). Liquid used was 45% aqueous solution of acrylic acid/tri-carboxylic acid copolymer. The mixture (powder/liquid=2.7/1.0) was used for preparing specimens for respective tests. Compressive strength (CS) testing was performed according to ISO9917-1. For translucency measurement, the mixture was allowed to set to obtain test specimens (15mm-diameter, 1mm-thickness), and Y values of specimens, measured before and after storage in water (37°C/24h) using spectrophotometric colorimeter, were used to calculate contrast ratio (CR). A GIC for filling (A2) was prepared using the novel 4.7µm FASG, and its CS and CR were compared to those of commercially-available products. Data were statistically analyzed (one-way ANOVA, Tukey’s test).
Results: CS of experimental GICs tended to increase with decrease of powder particle size; the powders with 3.4µm or 4.7µm particle size showed the highest strength. The CR tended to decrease (i.e. GIC became more translucent) with increase of powder particle size. The A2 GIC containing the novel 4.7µm FASG exhibited CS equivalent to that of commercially-available products, but higher translucency.
Conclusions: A set GIC contains glass-ionomer phase (GI-phase) and unreacted glass particles. Within the limitations of this study, GIC’s mechanical properties and translucency are likely to be complexly associated with the existence ratio of GI-phase and unreacted glass particles. The novel 4.7µm FASG-containing GIC for filling has higher translucency in initial setting phase, suggesting that the novel GIC can achieve esthetic restoration.
Methods: A novel FASG was milled to obtain experimental powders (refer to the table). Liquid used was 45% aqueous solution of acrylic acid/tri-carboxylic acid copolymer. The mixture (powder/liquid=2.7/1.0) was used for preparing specimens for respective tests. Compressive strength (CS) testing was performed according to ISO9917-1. For translucency measurement, the mixture was allowed to set to obtain test specimens (15mm-diameter, 1mm-thickness), and Y values of specimens, measured before and after storage in water (37°C/24h) using spectrophotometric colorimeter, were used to calculate contrast ratio (CR). A GIC for filling (A2) was prepared using the novel 4.7µm FASG, and its CS and CR were compared to those of commercially-available products. Data were statistically analyzed (one-way ANOVA, Tukey’s test).
Results: CS of experimental GICs tended to increase with decrease of powder particle size; the powders with 3.4µm or 4.7µm particle size showed the highest strength. The CR tended to decrease (i.e. GIC became more translucent) with increase of powder particle size. The A2 GIC containing the novel 4.7µm FASG exhibited CS equivalent to that of commercially-available products, but higher translucency.
Conclusions: A set GIC contains glass-ionomer phase (GI-phase) and unreacted glass particles. Within the limitations of this study, GIC’s mechanical properties and translucency are likely to be complexly associated with the existence ratio of GI-phase and unreacted glass particles. The novel 4.7µm FASG-containing GIC for filling has higher translucency in initial setting phase, suggesting that the novel GIC can achieve esthetic restoration.