Substrate masking ability of bilayer and monolithic ceramics used for complete crowns and the effect of association with an opaque resin-based luting agent

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Purpose: To evaluate the substrate masking ability of different ceramic systems used for complete crowns and assess the influence of their association with an opaque resin-based luting agent (OLA).

Methods: Eleven ceramic groups were tested (n = 10). Bilayer groups were: ZrPc — zirconia + porcelain; CAD-onHT — zirconia + high translucent lithium disilitace; CAD-onLT — zirconia + low translucent lithium disilicate; LDPc — high opaque lithium disilicate + porcelain. Monolithic groups were: TZ — high translucent zirconia; TLS — translucent, zirconia-reinforced lithium silicate; HTLS — high translucent, zirconia-reinforced lithium silicate; LTLD — low translucent lithium disilicate; HTLD — high translucent lithium disilitace; LGC — leucite-reinforced glass ceramic; FC — feldsphatic ceramic. The substrates adopted were resin composites shaded A1 (control), A3.5 and C4; coppery and silvery metals. Color differences (ΔE₀₀) and translucency parameter (TP₀₀) were assessed with the CIEDE2000 formula. ΔE₀₀ was obtained assessing the ceramic influence only and in association with OLA.

Results: Zirconia groups presented lower ΔE₀₀ and TP₀₀. CAD-on structures associated to OLA led to the lower ΔE₀₀ when tested over metals. ΔE₀₀ for LDPc were similar to zirconia when associated to OLA. Monolithic groups presented significant higher ΔE₀₀ and TP₀₀ compared to bilayers, with ΔE₀₀ below the acceptability threshold only when associated to OLA over substrate shade A3.5.

Conclusions: Ceramic type and the white-opaque resin-based luting agent presented a significant effect on the substrate masking ability. All the discolored substrates tested are adequately masked with veneered zirconia or with LDPc (preferably associated to OLA). The CAD-on technique associated with OLA improved the masking ability over metallic substrates.