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

Objective. To evaluate 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. Material and methods. Artificial darkened lateral incisors with 1mm-thick veneers preparations were used to evaluate color masking of different resinous materials, with or without opacifiers: IPS Empress Direct (ED) with or without ED Opaque; and Essentia (ES) with or without ES Masking Liner. For the RTP test; disc-shaped specimens were performed and evaluated with a spectrophotometer (VITA Easyshade) against black and C4 backgrounds. Color differences were calculated using the CIEDE2000 formula (ΔE00). Results. The dentin layer thickness presented no influence on the ΔE00 (P>.05) of the ED group with opacifier; without opacifier, 0.3mm dentin thickness presented higher ΔE00 than 0.8mm layer (P=0.000). For 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 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 was observed with the increase of dentin thickness (P<.05). ED groups with opacifier presented significant lower ΔE00 than ES groups (P<.05). It was observed a significant decrease in ΔE00 for all groups with an opacifier (P<.05). Conclusions. ED combinations with 0.3mm with opacifier and 0.6mm or higher without opacifier were sufficient to mask a C4 background, while ES combinations could not acceptably mask the substrate, according to the acceptability threshold determined. Dentin thicknesses significantly increase at the same pattern as ΔE00 decreases. A black background promoted increased ΔE00 values than a C4 background.