Masking Ability of Bleach-Shade Ceramics Applied Over Different Substrates: Influence of Opaque Stain Application and Ceramic Thickness.

OBJECTIVE

To investigate the masking ability of dental ceramics of bleaching shade applied over discolored substrates, based on ceramic thickness and application of opaque stains at the ceramic intaglio surface.

MATERIALS AND METHODS

Ceramic specimens of shade BL2 with 1-, 1.5-, and 2-mm thicknesses were produced with: lithium disilicate (IPS e.max CAD, LT), leucite (Empress CAD, LT), monolithic zirconia (Prettau Anterior), and zirconia bilayers (IPS e.max Zircad MO + lithium disilicate). Opaque stains were applied to the intaglio surfaces: Ivocolor White for glass-ceramics and coloring liquids White and White Plus for zirconia. Specimens without stains served as controls. Color differences (ΔE) were investigated over the substrates A1 (reference), A3, A4, C2, C4, coppery, and silvery metals. The outcomes were compared with ΔE thresholds. Data for translucency parameter (TP), Whiteness Index for Dentistry (WI), lightness, chroma, and hue angle were also presented. Two-way ANOVA and Tukey post hoc test (α = 0.05) were used for data analyses.

RESULTS

In general, the use of opaque stains associated with the increase of ceramic thickness led to a significant increase in lightness and chroma, and a reduction in hue angle and TP (p < 0.001). With stains, WI significantly decreased in lithium disilicate and leucite and increased in zirconia (p < 0.001). Zirconia bilayer with 1.5 mm of thickness associated with the stain White Plus led to excellent color matching for substrates A3, A4, and C2, acceptable color matching for substrate C4, and a moderately unacceptable mismatch for coppery and silvery metals. All types of ceramics of 1 mm of thickness associated with opaque stains led to acceptable color matching for substrates A3, A4, and C2. Monolithic and bilayer zirconia of 2 mm associated with stain White Plus provided acceptable color matching for coppery metal.

CONCLUSION

The substrate masking ability of dental ceramics of bleaching shade was dependent on the ceramic thickness and the presence of opaque stain at the intaglio surface.

CLINICAL SIGNIFICANCE

The esthetical outcome of ceramic restorations of bleaching shade over discolored substrates can be improved with the use of opaque stains at the ceramic intaglio surface and the production of ceramic restorations of adequate thickness, which is dependent on the severity of substrate discoloration.