OBJECTIVES: The role of particle size and size distribution of glass powders in glass-ionomer cements (GICs) has been largely overlooked, being limited to demonstrations of the classical inverse size-strength relationship. This study investigated variation in properties of an experimental glass-ionomer cement when a combination of large ('Powder A') and small ('Powder B') particles was used. METHODS: Large- (mean size 9.60mum) and small-particle (3.34mum) glass powders were blended in various proportions and mixed with powdered polyacrylic acid to make a range of glass-ionomer powders. These powders were mixed with a glass-ionomer liquid (SDI Ltd, Australia) at powder to liquid ratios of 2:1, 2.5:1, and 3:1, and the resultant cements evaluated for working time, setting time, clinical handling, and compressive strength. Results were analysed by ANOVA. RESULTS: An increased proportion of smaller particles corresponded to higher strengths, and an increased proportion of larger particles with a decrease in viscosity of the unset cement. When 20-30% by weight of small particles was used, the paste demonstrated a peak in cohesion and working time, with a viscosity similar to commercial restorative GICs. SIGNIFICANCE: Optimisation of particle sizing and distribution may thus lead to glass-ionomer cements with improved clinical handling characteristics and greater strength, which may increase the longevity of the restoration.
OBJECTIVES: The role of particle size and size distribution of glass powders in glass-ionomer cements (GICs) has been largely overlooked, being limited to demonstrations of the classical inverse size-strength relationship. This study investigated variation in properties of an experimental glass-ionomer cement when a combination of large ('Powder A') and small ('Powder B') particles was used. METHODS: Large- (mean size 9.60mum) and small-particle (3.34mum) glass powders were blended in various proportions and mixed with powdered polyacrylic acid to make a range of glass-ionomer powders. These powders were mixed with a glass-ionomer liquid (SDI Ltd, Australia) at powder to liquid ratios of 2:1, 2.5:1, and 3:1, and the resultant cements evaluated for working time, setting time, clinical handling, and compressive strength. Results were analysed by ANOVA. RESULTS: An increased proportion of smaller particles corresponded to higher strengths, and an increased proportion of larger particles with a decrease in viscosity of the unset cement. When 20-30% by weight of small particles was used, the paste demonstrated a peak in cohesion and working time, with a viscosity similar to commercial restorative GICs. SIGNIFICANCE: Optimisation of particle sizing and distribution may thus lead to glass-ionomer cements with improved clinical handling characteristics and greater strength, which may increase the longevity of the restoration.
Authors: Rania M Khashaba; Mervet M Moussa; Donald J Mettenburg; Frederick A Rueggeberg; Norman B Chutkan; James L Borke Journal: Int J Biomater Date: 2010-07-29
Authors: Júlio C M Souza; Joel B Silva; Andrea Aladim; Oscar Carvalho; Rubens M Nascimento; Filipe S Silva; Antonio E Martinelli; Bruno Henriques Journal: Open Dent J Date: 2016-03-15