Document Type : Original Article(s)
Authors
1
Department of Restorative Dentistry, Head of the Dental Materials Research Center, Faculty of Dentistry, Babol University of Medical Sciences, Babol, Iran
2
Department of Endodontics, Faculty of Dentistry, Mazandaran University of Medical Sciences, Sari, Iran
3
Department of Restorative Dentistry, Faculty of Dentistry, Mazandaran University of Medical Sciences, Sari, Iran
Abstract
Statement of Problem: One of the factors affecting the degree of polymerization of light-cured composites is the type of light-curing unit used. In addition, physicomechanical properties of composite resins depend on the degree of conversion and polymerization.Objectives(s): Since the type of initiator in new composite resins is not explained by manufacturers, this study is an attempt to compare the depth of hardening, with two LED and QTH light-curing units.Materials and Methods: Fifteen samples prepared from Gradia Direct and Filtek Z250, both of which being universal. All were cured with QTH (Astralis 7) and LED (Bluephase C8) light-curing units. Then, each composite resin sample was cured with both types of light-curing units. All the samples were moulded in polyester resin and cut from the middle by a disk. The hardness of the cut area was evaluated at 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5 and 4-mm depth intervals and also at the same interval as the width of the sample, with Vickers hardness machine, while the samples were placed in a darkroom. Data were statistically analyzed using one-way ANOVA, two-way ANOVA, t-test and post hoc Tukey tests with SPSS, version 16.Results: Filtek Z250 was harder than Gradia Direct at all the depth with both light-curing units. The hardness of Filtek Z250 sample cured with Astralis 7 was higher than that cured with LED, but with Gradia Direct the LED unit resulted in higher hardness. Curing depth was not significantly different between the groups (P=0.109).Conclusions: Vickers hardness number for both composites used in this study in an acceptable range for clinical implications. The composites` composition is important to be considered for selection of light unit. Based on the findings of the present study, LED did not present more curing depth compared with QTH.
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