## 4 Discussion  
The findings derived from this investigation provide evidence for the rejection of the null hypothesis posited, as the silver nanoparticles (AgNPs) demonstrated a crucial function in safeguarding the silicone material. The color of the A-2186 maxillofacial silicone was notably altered as a result of artificial aging, particularly leading to a substantial change in color (\(\Delta\)E \(>\) 3.0) within the red spectrum. In addition, it is worth noting that all groups demonstrated a variation in color, including colorless, red, blue, mocha, and mixture. Despite the fact that certain color alterations in the control group exceeded the perceptibility threshold of 1.1 by a significant margin, only the red color exhibited a level of significance surpassing the acceptability threshold of 3.0 [47]. This implies that the color change in the silicone specimens in the present study is not clinically significant, except for the red color. The perceptibility threshold is defined as the color difference that the human eye notices. In contrast, the acceptability threshold is considered the color difference that is acceptable in terms of aesthetics [48]. Changing the material's color in a clinical setting is permissible if the change is below the acceptable threshold and above the detectable threshold. This indicates that the change in a material's color can be noticed clinically while being aesthetically appealing. Consistent with the anticipated outcomes, the color of the additive-free silicone samples that were artificially aged exhibited a noticeable alteration. Silicone has the ability to undergo UV radiation absorption, resulting in the fragmentation of polymer chains and the generation of free radicals [30]. After 500 h of artificial aging, the unpigmented group exhibited a considerable color change in relation to the perceptibility threshold. [PERSON] et al. [49] reported that the unpigmented group underwent a significant color change in their study, attributing it to the continual chemical polymerization. Our findings follow prior studies [25; 50] that found colorless silicone to be susceptible to chromatic alteration, even after the addition of pigments and nano-oxides. The red color showed a significant color change in terms of both perceptibility and acceptability (\(p<0.000\)) [48; 51; 52]. Due to the findings of [PERSON] et al., red was selected as the intrinsic color for this study. In their study, the red pigment was shown to have the most significant detrimental influence on the color stability of silicone elastomers [29]. [PERSON] et al. [2] studied the effect of UV light exposure on the color of dry-pigmented maxillofacial elastomers. They discovered that after 400 h of exposure, red cosmetic dry earth pigment exhibited considerable color changes. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Pigments**} & \multirow{2}{*}{**Control**} & \multicolumn{3}{c}{**AgNPs (\%)**} \\ \cline{3-5}  & & **0.1 AgNPs** & **0.15 AgNPs** & **0.2 AgNPs** \\ \hline Colorless & \multirow{2}{*}{**2.41** (0.22)} & **2.13** (0.60) & **2.03** (0.51) & **1.85** (0.72) \\ (Silicone only) & & **28.32** (0.83) & **15.47** (0.76) & **14.65** (1.32) & **12.88** (1.58) \\  Blue & **3.15** (0.44) & **2.14** (0.55) & **1.93** (0.53) & **1.49** (0.28) \\  Mocha & **2.44** (0.24) & **2.02** (0.41) & **1.74** (0.46) & **1.44** (0.49) \\  Mix & **2.70** (0.26) & **2.37** (0.58) & **2.16** (0.24) & **1.92** (0.22) \\ (Red + Blue + Mocha) & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Means and standard deviations of \(\Delta\)E\({}^{*}\) for control and AgNPs groups after 500 h of aging. \begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **Sum of Squares** & **df** & **Mean Square** & **F** & **Sig.** \\ \hline Between Groups & 14418.484 & 40 & 360.462 & 894.406 & 0.000 \\ Within Groups & 115.666 & 287 & 0.403 & & \\ Total & 14534.150 & 327 & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: ANOVA results for color changes (\(\Delta\)E\({}^{*}\)) after artificial aging.