[Light-emitting diodes (LED) technology applied to the photopolymerization of resin composites]

An adequate polymerization of resin composites can significantly contribute to increase the longevity of a restoration. In this field, the choice of the operative technique and the characteristics of the lamp are very important. The aim of this review was to evaluate the effectiveness of cure of the light-emitting diodes (LED) lamps comparing them to the others currently available for resin composites photopolymerization. At present, halogen lamps are the most commonly used light sources, but this technology does not allow further developments; even plasma arc and laser lamps have some drawbacks. The innovative LED technology, based on semiconductors, opened new and interesting views in the field of photopolymerization; to the advantages of a soft-start polymerization they add the safety, efficiency, economy and long lifetime of LED light. A careful review of the literature revealed that, although their lower emission of light, these lamps are capable of a polymerization qualitatively comparable to other light sources. Physical and mechanical properties, degree of conversion, depth of cure and final hardness of the composites cured with a LED light are similar to the values achieved with the halogen lamp, whereas the temperature increase is significantly lower and does not pose a threat to the pulp tissue. Undoubtedly, more tests of the mechanical properties of composites processed with LED units need to be carried out but, as the technology improves, LED curing will become an interesting alternative to existing curing methods.