Journal of Dental Research, Vol 67, 831-835, Copyright © 1988 by International & American Associations for Dental Research Online Journals
Wear and microhardness of a silver-sintered glass-ionomer cement
J. E. McKinney, J. M. Antonucci and N. W. Rupp
National Bureau of Standards, Gaithersburg, Maryland 20899.
Knoop Hardness and pin-and-disc-wear measurements were made on a commercial
silver-sintered glass-ionomer cement. The objective was to determine
whether the incorporation of a bonded-metal-to-glass filler would enhance
durability as determined by the above measurements. As with the previous
work on conventional (non-metalized) glass-ionomer cements, the specimens
were preconditioned at 37 degrees C in air, water, 0.02 mol/L lactic acid
(pH 2.67), and heptane. The influence of these media on the microhardness
of the silver-sintered material was about the same as that on the
conventional materials. Storing in air produced dehydration, which
increased the hardness considerably. Heptane storage increased the hardness
less, but this increase is attributed to continued curing during storage.
After storage in water, the hardness was essentially unchanged; the
influence of increased cure is believed to be offset by softening or
plasticization from water uptake. Lactic acid produced a decrease in
hardness from chemical dissolution as seen from the SEM observations. In
most cases, in particular for the air-stored specimens, the wear resistance
was enhanced markedly over that of the conventional materials evaluated
previously. The exception was the lactic acid-stored specimens for which
little, or no, improvement was observed during early periods of wear. The
incorporation of silver appeared to provide lubrication, thus reducing
wear. However, catastrophic failure from brittle fracture was still a
problem, but its occurrence was less frequent.
