Characterization method of photopolymerization kinetics of two dental composite resins using two types of light sources

The aim of this study was to characterize to photopolymerization curves of two dental composite resins (Z100® from 3M ESPE Corp., and Tetric® Ceram® from Ivoclar Vivadent Corp.) according to the time exposure, the curing mode and the type of light source (halogen versus light emitting diode light curing units). The behavior and durability of composite resin do not depend only on their global shrinkage but also on their kinetic of polymerization which was studied with a mercury dilatometer. Four characteristics could be highlighted: the initial dilatation peak, the angle formed by the initial drop of shrinkage with the vertical axis, the angle formed by the secondary drop of shrinkage with the vertical axis and the intersection point between the two drops of shrinkage. The temperature rise was studied using a thermocouple to determine the position of the temperature peak in regard to the dilatation peak of the shrinkage curve. This is of interest for the clinical use of dental resin and light sources as well as curing procedures.