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

Hoon-Sang Chang,Sung-Ok Hong

doi:10.1590/1807-3107bor-2014.vol28.0016

Hoon-Sang Chang, Sung-Ok Hong

Open Access

https://doi.org/10.1590/1807-3107bor-2014.vol28.0016

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Abstract

The purpose of this study was to assess the color of layered resin overlays and to test the early microhardness of dual cure resin cement (DCRC) light cured through the layered resin overlays. Resin overlays 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), and the A3, E3, and T1 shades of Sinfony (Group 3L) using one, two, and three layers, respectively (n=7). Each layer of the resin overlays was set in equal thickness. The color of the resin overlays was measured with a colorimeter and compared with an A3 shade resin denture tooth. DCRC was light cured through the resin overlays, and the early microhardness of the DCRC was measured. The ΔE value between the denture tooth and the resin overlays and the Vickers hardness number (VHN) of the DCRC were analyzed with one-way ANOVA and Tukey's HSD test. The color differences were 8.9±0.5, 5.3±1.0, and 7.3±0.5 and the VHNs were 19.4±1.1, 21.1±0.9, and 29.3±0.6 for Groups 1L, 2L, and 3L, respectively. Therefore, to match the designated tooth color of resin inlays and to increase the early microhardness of DCRC, layered resin inlays are more appropriate than single-dentin-layer resin inlays. However, the translucent layer should be used cautiously because the color difference of resin inlays with a translucent layer was affected more than those without a translucent layer.

Highlights

Dual cure resin cements (DCRCs) are intended to polymerize when they are exposed to curing light and when the base and catalyst components are mixed together.[1]
Resin overlays fabricated with a single dentin layer showed markedly perceptible color differences compared to a shade A3 resin denture tooth
The early microhardness of DCRC light cured through resin overlays with a single dentin layer had the lowest Vickers hardness number (VHN) values

Summary

Introduction

Dual cure resin cements (DCRCs) are intended to polymerize when they are exposed to curing light and when the base and catalyst components are mixed together.[1]. Esthetics in the posterior region are not as critical as in the anterior region, and the shade guides of many direct resin composite systems recommend using a single dentin layer or dentin and enamel layers for posterior restorations. Some indirect resin composite systems are composed of dentin, enamel, and translucent layers, and manufacturers recommend. The layering technique attempts to replace dentin and enamel by placing a more translucent layer over a more opaque layer of resin composite to create a perception of depth from within the restoration.[7] studies have reported poor compatibility of resin composites of identical shade designation between pairs of shades,[8,9] and the color of the restoration was influenced by the optical properties of the enamel layer as well as those of the dentin layer.[7,10]

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