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Degree of conversion and microhardness of bulk-fill dental composites polymerized by LED and QTH light curing units
Maryam Pirmoradian1, Tabassom Hooshmand1, Siavash Jafari-Semnani2
1Department of Dental Biomaterials, School of Dentistry, Research Center for Science and Technology in Medicine, Tehran University of Medical Sciences, Tehran, Iran.
Objectives:
The degree of monomer conversion is crucial in determining the mechanical and clinical performance of dental resin composites. This study investigated the polymerization adequacy of two bulk-fill resin composites polymerized by Quartz-Tungsten-Halogen (QTH) and Light Emitting Diode (LED) light curing units at different depths.
Methods:
Two bulk-fill resin composites (X-tra Fil; Voco and Tetric N-Ceram Bulk-fill; Ivoclar-Vivadent) with diameters of 7 mm and thicknesses of 1-4 mm were prepared and light-cured by LED or QTH. Then, the degree of conversion (DC) and microhardness of the two bulk-fill composites were evaluated.
Results:
The microhardness of X-tra fill was significantly higher than that of Tetric N-Ceram polymerized by LED or QTH. The microhardness and DC of X-tra fil exhibited no significant difference among the increments regardless of type of light source. The DC, however, significantly decreased in deep increments for Tetric N-Ceram polymerized by QTH.
Conclusions:
The polymerization efficacies of the two bulk-fill composites were different in terms of the depth of cure and type of light source. The DC and microhardness of the X-tra fill bulk-fill composite polymerized by either QTH or LED did not decrease up to a thickness of 4 mm. Thus, new generations of LED light sources are better options for polymerizing the bulk-fill resin composites than QTH.
