Methods: Two types of glass ionomer cements were used in this experiments: Fuji IX FAST (GC, Japan) and Fuji II LC (GC, Japan). The disc form cement samples with minimum thickness of 1 mm were prepared according to the manufactures instructions. Electrical conductivity changes during the setting reaction of glass ionomer cements were determined by impendance spectroscopy in the frequency range from 10 Hz to 1000 Hz, at room temperature. The Fuji II LC samples were measured with and without exposing to the curing light. Changes in electrical conductivity were monitored for 12 hours.
Results: The light cured Fuji II LC samples showed a rapid electrical conductivity decline at the beginning of the measurement, while the samples that were not light-cured showed a slower decrease. After that, the values of electrical conductivity assumed a constant value which was similar to those obtained with the light cured samples. A small difference in the electrical conductivity measured at 10 Hz and 1000 Hz was observed. The time dependent changes in the electrical conductivity of Fuji IX FAST were also evident. A sudden drop in electrical conductivity at the beginning of the reaction occurred, but somewhat later if compared to the Fuji II LC results.
Conclusion: This study reveals a decrease in the electrical conductivity at the begining of the reaction whereas after 15-20 min. the conductivity does not change. Time dependent electrical conductivity changes were conditioned by the degree of settings showing that in Fuji II LC networking occurs rapidly (within 3-5 min), while in Fuji IX FAST this process is three times longer (12-15 min).
Supported by CSF.