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Lasers in medical science

Effect of two lasers on the polymerization of composite resins: single vs combination.


PMID 25895056

Abstract

The selection of a light-curing unit for the curing composite resins is important to achieve best outcomes. The purpose of the present study was to test lasers of 457 and 473xa0nm alone or in combination under different light conditions with respect to the cure of composite resins. Four different composite resins were light cured using five different laser combinations (530xa0mW/cm(2) 457xa0nm only, 530xa0mW/cm(2) 473xa0nm only, 177xa0mW/cm(2) 457 + 177xa0mW/cm(2) 473xa0nm, 265xa0mW/cm(2) 457 + 265xa0mW/cm(2) 473xa0nm, and 354xa0mW/cm(2) 457 + 354xa0mW/cm(2) 473xa0nm). Microhardness and polymerization shrinkage were evaluated. A light-emitting diode (LED) unit was used for comparison purposes. On top surfaces, after aging for 24xa0h, microhardness achieved using the LED unit and the lasers with different conditions ranged 42.4-65.5 and 38.9-67.7xa0Hv, respectively, and on bottom surfaces, corresponding ranges were 25.2-56.1 and 18.5-55.7xa0Hv, respectively. Of the conditions used, 354xa0mW/cm(2) 457xa0nm + 354xa0mW/cm(2) 473xa0nm produced the highest bottom microhardness (33.8-55.6xa0Hv). On top and bottom surfaces, microhardness by the lowest total light intensity, 354 (177 × 2) mW/cm(2), ranged 39.0-60.5 and 18.5-52.8xa0Hv, respectively. Generally, 530xa0mW/cm(2) at 457xa0nm produced the lowest polymerization shrinkage. However, shrinkage values obtained using all five laser conditions were similar. The study shows the lasers of 457 and 473xa0nm are useful for curing composite resins alone or in combination at much lower light intensities than the LED unit.