Masking ability of a zirconia ceramic on composite resin substrate shades

Abstract

Background:Masking ability of a restorative material plays an important role to cover discolored tooth structure; however, this ability has not yet been well understood in zirconia-based restorations. This study assessed the masking ability of a zirconia ceramic on composite resin substrates with different shades.Materials and Methods:Ten zirconia disc specimens, with 0.5 mm thickness and 10 mm diameter, were fabricated by a computer-aided design/computer-aided manufacturing system. A white substrate (control) and six composite resin substrates with different shades including A1, A2, A3, B2, C2, and D3 were prepared. The substrates had a cylindrical shape with 10 mm diameter and height. The specimens were placed onto the substrates for spectrophotometric evaluation. A spectrophotometer measured the L*, a*, and b* values for the specimens. ΔE values were calculated to determine the color differences between the groups and the control and then were compared with a perceptional threshold (ΔE = 2.6). Repeated measures ANOVA and Bonferroni tests were used for data analysis (P < 0.05).Results:The mean and standard deviation of ΔE values for A1, A2, A3, B2, C2, and D3 groups were 6.78 ± 1.59, 8.13 ± 1.66, 9.81 ± 2.64, 9.61 ± 1.38, 9.59 ± 2.63, and 8.13 ± 1.89, respectively. A significant difference was found among the groups in the ΔE values (P = 0.006). The ΔE values were more than the perceptional threshold in all the groups (P < 0.0001).Conclusion:Within the limitations of this study, it can be concluded that the tested zirconia ceramic could not thoroughly mask different shades of the composite resin substrates. Moreover, color masking of zirconia depends on the shade of substrate.

Color Aspect of Monolithic Zirconia Restorations: A Review of the Literature

“…Moreover, Jirajariyavej et al suggested the use of yellow‐shaded zirconia abutments along with increasing the thickness of the ceramic restoration to produce a more‐esthetic color. To compensate for the background aspect, several solutions are proposed: using backgrounds with the color close to the target color, masking backgrounds with proper cements, and increasing the zirconia thickness …”

“…To achieve optimum esthetics for monolithic zirconia restorations in patients needing a composite resin foundation, the corresponding restoration shade should be chosen for the foundation . When a custom post and core is the option, the use of a non‐precious gold‐colored alloy or a zirconia ceramic is recommended rather than a nickel‐chromium alloy .…”

Effect of Resin Cement Brand on the Color of Zirconia‐Based Restorations

“…A well‐documented spectrophotometer (SpectroShade Micro; MHT Optic Research AG, Verona, Italy) was used for all color measurements. A silicone putty (Speedex; Coltene, Altstatten, Switzerland) was molded to the mouthpiece of the spectrophotometer to match the conditions for all specimens, to provide a seat for the backgrounds, and to avoid external light . Each veneered zirconia specimen was assigned to a background specimen, and color measurements were conducted before cementation (zirconia specimens were properly placed on backgrounds without an intermediate) and after cementation.…”

“…Considering the thickness and translucency of both compartments, light transmission through these restorations can be anticipated . Therefore, underlying structures such as dental backgrounds and cements may affect the color of zirconia‐based restorations …”

Choice of resin cement shades for a high-translucency zirconia product to mask dark, discolored or metal substrates

“…In clinical restorations, the recommended range of thickness for monolithic zirconia is 0.5 – 2.0 mm 13. It has also been found that 0.5-mm low-translucency zirconia ceramic could not mask tooth discoloration 14. An increase in thickness improves the masking ability of translucent zirconia 15.…”