Influence of the powder/liquid ratio and storage time of conventional glass ionomer cements in diametral tensile strength

Resumo

The Glass Ionomer Cements (GICs) are the most
versatile dental material with extensive clinical indication. However,
the mechanical strength of conventional GICs (C-GICs) is still
unsatisfactory under areas of masticatory forces. Objective: To
evaluate the influence of C-GIC proportioning system (powderliquid and encapsulated) and storage period (1h, 24h and 7 days)
on Diametral Tensile Strength (DTS). Material and methods: The
two variables were tested in relation to C-GIC (Riva Self Cure,
SDI, Australia). The following proportioning systems were tested:
powder-liquid by weight (g:g) and powder-liquid by volume (flat
scoop: drop) and encapsulated system (pre-dosed capsules). Five
C-GIC specimens were prepared, according to ISO specification
#9917 for each variable to be studied. The specimens were stored
in plastic containers containing distilled water and kept at 37ºC
and 100% humidity until the mechanical testing in a universal
testing machine (Instron Corp., USA) at a speed 0.5 mm/min. The
data were submitted to two-way ANOVA and Tukey test for multiple
comparisons (α = 0.05). Results: The proportioning system (P <
0.0001) and storage time (P < 0.0001) were significant predictors of
DTS, however with no interaction between these factors. Conclusion:
The DTS of C-GICs was influenced by storage time (1 hour < 24
hours < 7 days) and by the proportioning system only for the initial
period of its setting reaction.