The effect of particle size distribution on an experimental glass-ionomer cement.
OBJECTIVE
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.


CONCLUSIONS
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.
Prentice
Leon H
LH
School of Dental Science, University of Melbourne, Parkville, Vic. 3010, Australia.
Tyas
Martin J
MJ
Burrow
Michael F
MF
D000704:Analysis of Variance; D019245:Compressive Strength; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006244:Hardness; D008422:Materials Testing; D010316:Particle Size; D011208:Powders; D014783:Viscosity
D005899:Glass Ionomer Cements; D011208:Powders