Influence of Opacifiers and Different Dentin Thicknesses on the Optical Properties of a Darkened Teeth with Limited Sound Tissue Reduction

This study evaluated the color-masking and relative translucency parameter (RTP) of increasing dentin thicknesses from different resin composites, with or without opacifiers, on a veneer dental preparation and resin disks. Artificially darkened lateral incisors with 1-mm-thick veneer preparations were used for the different materials: IPS Empress Direct (ED; Ivoclar Vivadent) with or without ED Opaque (Ivoclar Vivadent), and Essentia (ES; GC) with or without ES Masking Liner (GC). For the RTP test, disk-shaped specimens were made and evaluated with a spectrophotometer (VITA Easyshade) against black and C4 backgrounds. Color differences (ΔE00) were calculated using the CIEDE-2000 formula. The dentin layer thickness presented no influence on the ΔE00 values (P > .05) of the ED group with opacifier; without opacifier, 0.3-mm dentin thickness presented higher ΔE00 values than 0.8-mm dentin layer (P = .000). For the ES group, with and without opacifier, there was a significant decrease in ΔE00 with the increase of dentin thickness (P < .05). All ED groups presented lower ΔE00 values than the ES groups (P < .05). All groups showed perceptible color differences, but some ED groups showed acceptable values. For RTP comparisons, a decrease in the ΔE00 value was observed with the increase of dentin thickness (P < .05). ED groups with opacifier presented significantly lower ΔE00 values than ES groups (P < .05). A significant decrease in ΔE00 values was observed for all groups with an opacifier (P < .05). ED combinations with 0.3-mm thickness and opacifier and with 0.6-mm thickness or higher without opacifier were sufficient to mask a C4 background, while ES combinations could not acceptably mask the substrate, according to the determined acceptability threshold. Dentin thickness significantly increases at the same pattern that the ΔE00 value decreases. A black background promoted greater ΔE00 values than a C4 background.