Effects of layering technique on the shade of resin overlays and the microhardness of dual cure resin cement

Abstract

The purpose of this study was to assess the color of layeredresin overlays and to test the early microhardness of dual cure resincement (DCRC) light cured through the layered resin overlays. Resinoverlays of 1.5 mm thickness were fabricated with the A3 shade of Z350(Group 1L), the A3B and A3E shades of Supreme XT (Group 2L), andthe A3, E3, and T1 shades of Sinfony (Group 3L) using one, two, andthree layers, respectively (n = 7). Each layer of the resin overlays wasset in equal thickness. The color of the resin overlays was measuredwith a colorimeter and compared with an A3 shade resin denture tooth.DCRC was light cured through the resin overlays, and the early microhardnessof the DCRC was measured. The ΔE value between thedenture tooth and the resin overlays and the Vickers hardness number(VHN) of the DCRC were analyzed with one-way ANOVA and Tukey'sHSD test. The color differences were 8.9 ± 0.5, 5.3 ± 1.0, and 7.3 ± 0.5 andthe VHNs were 19.4 ± 1.1, 21.1 ± 0.9, and 29.3 ± 0.6 for Groups 1L, 2L, and3L, respectively. Therefore, to match the designated tooth color of resininlays and to increase the early microhardness of DCRC, layered resininlays are more appropriate than single-dentin-layer resin inlays. However,the translucent layer should be used cautiously because the colordifference of resin inlays with a translucent layer was affected morethan those without a translucent layer.