The majority of modern composite restorative materials require light activation for polymerization. Variables affecting light energy absorption by the composite have been examined for their effect on the polymerization contraction. Since the polymerization contraction is closely associated in a complex way to the degree of cure of the restoration, this parameter served as an empirical indicator for the extent of polymerization. Variables included the composite shade, distance between the light source and composite sample, and light intensity. Three resin composites are evaluated. Post-gel polymerization contraction was evaluated using a strain gauge method. Curing light intensity diminished rapidly for distances greater than 2 mm between the tip of the light guide and material surface. A linear relationship was demonstrated between polymerization contraction and light intensity. The polymerization contraction of a microfilled composite and posterior composite, using a constant curing time and light intensity, decreased linearly with increasing sample thickness. Less than optimal light output of the curing light source can be compensated by increasing application time within reasonable limits.
- Light curing