Translucency and Masking Ability of CAD / CAM Milled Denture Base Resins of Different Shades and Thicknesses Against Metal Substrates

Objective To evaluate the translucency and masking ability of CAD/CAM milled denture base resins of different shades and thicknesses against gold‐ and silver‐colored metal substrates. Materials and Methods Two independent experiments were conducted using separate specimens. Circular specimens (Φ10 mm) were fabricated from five shades (P1–P5) of CAD/CAM milled denture base resin at thicknesses of 1, 2, 3, and 5 mm ( n = 8). For the 1‐, 2‐, and 3‐mm specimens, the color coordinates were measured against white and black backgrounds, as well as gold‐ and silver‐colored metal substrates. The 5‐mm specimens superimposed on the black background were defined as the baseline color reference for each shade. The translucency parameter (TP 00 ) was calculated based on measurements against white and black backgrounds, and the color difference (Δ E 00 ), which represents the masking ability of the respective specimen, was calculated by comparing measurements against the metal substrates with the corresponding baseline color reference. Analysis of variance was used for statistical analysis, and exploratory correlation analyses were used to assess the association between baseline color coordinates and Δ E 00 ( α = 0.05). Results Both TP 00 and Δ E 00 values significantly decreased with increasing thickness for all shades, and all thickness‐related ΔTP 00 values exceeded the translucency acceptability threshold (TAT = 2.62). For the gold‐colored metal substrate, the Δ E 00 values at 1 mm exceeded the acceptability threshold (AT = 2.8) for all shades. At 2 mm, the Δ E 00 values were below AT for the P1 and P3 shades but remained above AT for the other shades. At 3 mm, the Δ E 00 values were below AT but remained above the perceptibility threshold (PT = 1.1) for P1–P4, whereas P5 remained slightly above AT. For the silver‐colored metal substrate, the Δ E 00 values at 1 mm exceeded AT for all shades. At 2 mm, they were below AT but remained above PT for all shades, whereas at 3 mm, they were below PT for all shades except P2. Generally negative correlations were observed between the color coordinates and Δ E 00 values for the gold‐colored metal substrate, whereas positive correlations were mainly observed for the silver‐colored metal substrate. Conclusions Masking ability significantly increased with greater material thickness, a trend closely associated with reduced translucency. It was also influenced by both the resin shade and the metal substrate. The P3 shade provided the best masking ability for the tested gold‐colored brass substrate. Under the present in vitro conditions, the tested silver‐colored pure titanium substrate generally produced lower color differences than the tested gold‐colored brass substrate. Clinical Significance Under the present in vitro conditions, a resin thickness of 2 mm may be considered a practical option for masking the tested silver‐colored pure titanium substrate. For the tested gold‐colored brass substrate, masking at 2 mm was shade‐dependent; therefore, careful shade selection or increased resin thickness may be required.