This study evaluated the effects of opaque porcelain (OP) on color parameters and aesthetic outcomes of all-ceramic implant restorations with varying abutment types and restoration thicknesses. Four types of zirconia discs were fabricated:(A) 1.5 mm zirconia; (B) 1.4 mm zirconia + 0.1 mm OP; (C) 2.0 mm zirconia; (D) 1.9 mm zirconia + 0.1 mm OP. These discs were bonded to titanium (t) or all-ceramic (c) backgrounds to form At, Ac, Bt, Bc, Ct, Cc, Dt, and Dc specimens,to simulate the aesthetic results of implant restorations with or without OP on titanium or all-ceramic abutments. The assembled specimens were placed at the center of a dark backboard in a specialized constructed photography platform, and a professional camera was used to acquire images of the specimens. Eight regions of interest on the image were selected, and color parameters in the form of L*, a*, and b* values and variations determined via the CIELAB color measurement system were analyzed using Adobe Photoshop software.Color differences (ΔE) between samples were quantified. Statistical comparisons of color parameters were conducted using the Kruskal-Wallis H test and Welch's t-test. There were significant differences in L*, a*, and b* between all-ceramic and titanium backgrounds in all types of zirconia specimens (p < 0.001). The application of OP influenced the brightness and chroma of zirconia restorations on titanium backgrounds. ΔE values between restorations with metal substrate and OP, and those with all-ceramic substrate but without OP, (△E (Ac/Bt)= 1.99 ± 0.86; △E(Cc/Dt)= 1.31 ± 0.83) indicated that OP effectively mitigated the color compromise caused by metallic implant abutments. The greater the thickness of the restoration, the smaller the color difference caused by the titanium background. This study revealed that titanium abutments can affect the color of implant-supported restorations. The application of OP on restorations reduces the titanium abutment's color impact, and this effect improves with increased zirconia thickness.
Sun et al. (Wed,) studied this question.