Ma. Cattanilorente et al., MECHANICAL-BEHAVIOR OF GLASS-IONOMER CEMENTS AFFECTED BY LONG-TERM STORAGE IN WATER, Dental materials, 10(1), 1994, pp. 37-44
Objectives. The early strength of glass ionomer cements was investigat
ed previously (Cattani et al., 1993). Using the same set of glass iono
mer cements, this study was designed to determine if mechanical proper
ty degradation occurred after an extended period of storage in water.
Methods. In the present study, the effect of aging in water on the com
pressive, tensile and flexural strengths of twelve commercial glass io
nomer cements was evaluated at different time intervals after the begi
nning of the setting reaction. The aging periods varied from 24 h to 1
2 mon. Results. The results show that the mechanical properties of the
tested materials are in some cases affected by long-term aging in wat
er. The evolution of strength follows distinct patterns of change. It
has been established that the glass ionomer cements are neither charac
terized by a continuous increase nor a continuous decrease in strength
. Most of the materials tested maintained a constant strength. However
, several of them first display an improvement of the mechanical stren
gth followed by a reduction. In this case, the 24 h and the 12 mon str
engths are usually similar. Significance. The aging mechanisms of glas
s ionomers are complex. Strengthening probably results from additional
crosslinking and build-up of a silica gel phase, whereas weakening ma
y result from erosion and plasticizing effect of water.