Influence of zirconia base and shade difference on polymerization efficiency of dual-cure resin cement

The aim of this study was to investigate the polymerization efficiency of dual-cured resin cement beneath different shades of zirconia-based feldsphathic ceramic restorations.Five translucent zirconia (Zirkonzahn) discs (4.0-mm diameter, 1.2-mm height) were prepared. Feldsphathic ceramic (1.2 mm) (Noritake Cerabien Zr) in 5 shades (1M2, 2M2, 3M2, 4M2, 5M2) was applied on the zirconia discs. Twelve dual-cure resin cement specimens were prepared for each shade, using Panavia F 2.0 (Kuraray) in Teflon molds (4.0-mm diameter, 6.0-mm height), following the manufacturer's instructions. Light activation was performed through the zirconia-based ceramic discs for 20 seconds, using a quartz tungsten halogen curing device (Hilux 200) with irradiance of 600 mW/cm(2) . Immediately following light curing, specimens were stored for 24 hours in dry, light-proof containers. Vickers hardness measurements were conducted using a microhardness tester with a 50-g load applied for 15 seconds. The indentations were made in the cross sectional area at four depths, and the mean values were recorded as Vickers hardness number (VHN). Results were statistically analyzed with one-way ANOVA and Tukey HSD test (p0.05).A statistically significant decrease in VHN of the resin cement was noted with increasing depth and darkness of the shade (p0.05).Curing efficiency of dual-cure resin cement is mainly influenced by the lightness of the shades selected.