Setting contraction of vlc composite resins and glass-ionomer cements

摘要

The contraction kinetics of VLC composite resins and GIC was experimentally analyzed by scanning laser beam method. The length of the samples was 2-4 mm and the accuracy of the length measurements was +-1 mu m. The comparison of the experimental data with the analytical expression of the contraction in VLC materials required all the various steps (initiation, propagation and termination) of the polymerization process to be clearly distinguished. The experimental expression we used for the best fit included a time constant (0.12 min >= tau >= 0.50 min) and a corrective factor (0.25 >= beta >=0.75). For GIC maerials, the best fit of the theoretical expression of the contraction with the experimental values showed an additional exponential term, which characterized the evaporation process.