Effect of working time on the film thickness of dental resin cement

Abstract

Purpose. The objective of this study was to measure the film thicknesses of several resin cements altering the time duration between finishing of mixing and load.

Materials and Methods. Four kinds of resin cements were mixed according to the instruction manufacturers recommended and 5 kilogram loads were applied to the specimens for different lengths of time (20, 40, 60, 80, 100, 120, 140, 160 and 180 seconds. Film thicknesses were measured using a micrometer with an accuracy of 1 μm and the results were statistically analyzed by linear regression analysis and the working time recommended by manufacturers and the attained value calculated in this study were compared by Wilcoxon test (α = 0.05).

Results. The film thicknesses of all resin cements increased as the time intervals between finishing of mixing or dispensing of cements and loading become longer and showed linear function patterns with positive correlation. There were discrepancies between the working time we calculated based on the results and the values manufacturers recommended.

Conclusion. As the time interval between the finishing of the mixing and load application be longer, the film thickness of resin cement increases. When we use resin cements in clinics, we should note that the working time, the duration from after the mixing until the loading on the cement, at which the film thickness becomes 50 μm could be different from the value manufacturers recommend.