title: Effect of two lasers on the polymerization of composite resins: single vs combination.
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 473 nm 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 (530 mW/cm(2) 457 nm only, 530 mW/cm(2) 473 nm only, 177 mW/cm(2) 457 + 177 mW/cm(2) 473 nm, 265 mW/cm(2) 457 + 265 mW/cm(2) 473 nm, and 354 mW/cm(2) 457 + 354 mW/cm(2) 473 nm). Microhardness and polymerization shrinkage were evaluated. A light-emitting diode (LED) unit was used for comparison purposes. On top surfaces, after aging for 24 h, microhardness achieved using the LED unit and the lasers with different conditions ranged 42.4-65.5 and 38.9-67.7 Hv, respectively, and on bottom surfaces, corresponding ranges were 25.2-56.1 and 18.5-55.7 Hv, respectively. Of the conditions used, 354 mW/cm(2) 457 nm + 354 mW/cm(2) 473 nm produced the highest bottom microhardness (33.8-55.6 Hv). On top and bottom surfaces, microhardness by the lowest total light intensity, 354 (177 × 2) mW/cm(2), ranged 39.0-60.5 and 18.5-52.8 Hv, respectively. Generally, 530 mW/cm(2) at 457 nm produced the lowest polymerization shrinkage. However, shrinkage values obtained using all five laser conditions were similar. The study shows the lasers of 457 and 473 nm are useful for curing composite resins alone or in combination at much lower light intensities than the LED unit.
authors.affiliation: Department of Biomedical Engineering, School of Medicine, Yangsan, 626-770, Korea.
authors.forename: Jung-Hoon
authors.initials: JH
authors.lastname: Ro
authors.forename: Sung-Ae
authors.initials: SA
authors.lastname: Son
authors.forename: Jeong-kil
authors.initials: JK
authors.lastname: Park
authors.forename: Gye-Rok
authors.initials: GR
authors.lastname: Jeon
authors.forename: Ching-Chang
authors.initials: CC
authors.lastname: Ko
authors.forename: Yong Hoon
authors.initials: YH
authors.lastname: Kwon
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000138:chemical synthesis*; D055117:Curing Lights, Dental; D006244:Hardness; D054023:Lasers, Semiconductor; D008422:Materials Testing; D058105:Polymerization
chemical_list: D003188:Composite Resins; D017438:Bisphenol A-Glycidyl Methacrylate