Electrical Conductivity and Mass of GIC Immersed in Deionized Water

To investigate the change in electrical conductivity and mass of GIC samples with time of immersion in deionized water and to correlate the changes with different aging time under room conditions before immersion.

Method:

Impedance spectroscopy measurements were carried out on glass ionomer cements Fuji IX Fast, Ketac Molar and photosensitive Fuji II LC with different thickness (1, 2 and 3 mm) at room temperature in wide frequency range (10^-1-10⁶ Hz). After preparation the samples were aged under room conditions for shorter (1 hour) and longer (1 to 100 days) period of time before immersion in deionized water. Electrical conductivity and mass were measured every day during first week and than on 14^th and 30^thday of immersion.

Result:

Changes in electrical conductivity depend on the aging time of GIC samples before immersion. Electrical conductivity decreases with increasing aging time. After first day of immersion the electrical conductivity significantly increases for 1-2 orders of magnitude for all GIC samples aged for longer period of time. On the other hand, during further immersion the electrical conductivity varies only slightly. For Fuji IX Fast and Ketac Molar the electrical conductivity showed slight increase with increasing sample thickness. Mass measurements also showed the increase after first day of immersion reaching then a constant value during further immersion.

Conclusion:

Increase in electrical conductivity and mass of investigated GIC samples after immersion in deionized water depends on the previous aging time and thickness which have an effect on the amount of absorbed water.