Effects of dentin and enamel porcelain layer thickness on the color of various ceramic restorations

To investigate the effects of dentin and enamel porcelain layer thickness on the color of various ceramic restorations.

Eighty specimens (shade A2 and A3, n = 10) (20 mm in length, 4 mm in width, 1.5 mm in thickness respectively) of casting ceramic (EM); alumina ceramic (AL); zirconia ceramic (ZR); and porcelain-fused-metal (PFM) were prepared. The color distributions of each specimen were measured at 4 places using a spectroradiometer. The dentin/enamel porcelain (D/E) layer thicknesses of the 4 places were 0.8/0.2 mm, 0.6/0.4 mm, 0.4/0.6 mm, and 0.2/0.8 mm. The color differences (ΔE₀₀ ) between the specimens and the corresponding color shade tabs were calculated. Data were analyzed using three-way repeated-measures ANOVA and Holm-Sidak pairwise comparisons (a = 0.05). The acceptability threshold (AT) was used to analyze the results.

The minimum ΔE₀₀ values were 1.31 (0.6/0.4 mm for EM), 1.41 (0.8/0.2 mm for AL), and 1.92 (0.2/0.8 mm for ZR) for shade A2, and 0.93 (0.6/0.4 mm for EM), 0.89 (0.8/0.2 mm for AL), and 1.34 (0.8/0.2 mm for ZR) for shade A3. Most of them were below AT value (1.8). For AL and ZR (shade A2) and ZR (shade A3), the D/E layer thicknesses of 0.8/0.2 mm and 0.6/0.4 mm had lower ΔE₀₀ values than 0.4/0.6 mm and 0.2/0.8 mm (p ≤ 0.001).

The dentin/enamel porcelain layer thickness that was most color-matched to the shade tab was different for various ceramic restorations. The color of shade A2 AL and ZR and shade A3 ZR was closer to the shade tab when dentin porcelain was thicker than enamel porcelain.

Matching the shade of ceramic restoration to the shade tab color is a great challenge in esthetic dentistry. The dentin/enamel porcelain layer thickness is an important factor to influence the improved color matching.