Light-curing units, polymerization, and clinical implications.

A comprehensive review of the techniques of light initiation of dental composites with special attention to polymerization efficacy and shrinkage stress control is presented. Optimal setting of an average-sized composite restoration requires a certain quantity of light energy. The amount of energy depends on the characteristics of the light source used and the time of irradiation. Swift conversion with high-energy lamps is proportionally accompanied by rapid hardening and could negatively affect the marginal integrity of the adhesive restoration. However, preliminary stress measurements did not show an increase in the rate of stress development. Full conversion in the deeper areas of the restoration may not be possible if defects occur in one or more of the various lamp components. Prolonging the irradiation time could reduce this risk. A regular check on the energy output of the light source is recommended. Although the high-energy light sources with their extremely short irradiation times should be used in a more critical way than the conventional light sources, they save a considerable amount of time and facilitate bond application, leading to better restorations where isolation control need not be optimal.