## 3 Results  
### Surface Roughness (Ra)  
Figure 1 box plots present the median surface roughness (Ra) of the study groups at baseline (T0) and after whitening (T1). Three of the study groups (A, B, and D) demonstrated decreased Ra, whereas groups C, E, and F showed increased Ra after whitening. Group B and E specimens demonstrated the lowest (0.31, 0.19-0.79) and highest Ra (1.69, 0.84-3.19), respectively, after whitening. Among the groups whitened with OTC products, iWhite Dark Stains whitening kit (Group D) specimens demonstrated the lowest Ra (0.35, 0.19-1.01) and iWhite Dark Stains toothpaste (Group C) specimens demonstrated the highest Ra (0.48, 0.19-1.24) at T1. Group A specimens whitened with professionally supervised carbamide peroxide whitening product demonstrated Ra values of 0.36 (0.17-0.71). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Group Code/** & **Composition** & **Delivery Method/** \\
**Materials/Manufacturer** & **Composition** & **Duration of Use** \\ \hline Group A/ & & \\ OpalescenceTM PF/ & 10\% carbamide peroxide, 0.5\% potassium & Custom-made trays/ \\ Ultradent, South Jordan, UT, USA & nitrate, and 0.11\% fluoride ions (1000 ppm) & Eight hours per day for 10 days \\ \hline Group B & Distilled water & Immersed in 100 mL of distilled water \\ \hline Group C/ & Hydrated Silica, Sodium & \\ iWhite Dark Stains Toothpaste/ & Hexametaphosphate. Mannitol, Chondrus & Toothbrush/ \\ Sylphar, Deurle, Belgium & Crispus Powder, Charcoal Powder, Sodium & Two brushing cycles per day for 60 days \\  & Fluoride, Sodium saccharin. & \\ \hline Group D/ & Sodium bicarbonate, Carbomer, Polysorbate & \\
24 K White Charcoal Teeth-Whitening & 20, Sodium Hydroxide, Potassium Sorbate, & Whitening pen/One application per \\ Pen/ & Organic Coconut Charcoal. & day for two days \\ Active Wow, Tallahassee, FL, USA & & \\ \hline Group E & 0.25\% Citric acid & Manual treatment for one hour \\ \hline Group F/ & Hydrated Silica, Sodium & Ready-to-use trays/ \\ iWhite Dark Stains Whitening Kit/ & Hexametaphosphate. Mannitol, Chondrus & 20 min per day for 5 days \\ Sylphar, Deurle, Belgium & Crispus Powder, Charcoal Powder. & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Materials and group coding used in the study. Table 2 presents the significant difference in median Ra within and between the groups at T0 and T1 measurement intervals. When comparing Ra from T0 to T1 within each group separately, a statistically significant difference was demonstrated among the study groups (\(p<0.001\)) except for Group B (\(p=0.85\)). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Groups** & **T0 (Ra)** & **T1 (Ra)** & **Test of Significance (\(p\))** \\ \hline Group A & 0.5 (0.24–0.72) a & 0.36 (0.17–0.71) a & z = \(-\)2.13, \(p=0.032\) * \\ Group B & 0.32 (0.21–0.83) a & 0.31 (0.19–0.79) a & z = \(-\) 0.18, \(p=0.85\) \\ Group C & 0.46 (0.13–1.03) a & 0.48 (0.19–1.24) a & z = \(-\)3.30, \(p=0.001\) * \\ Group D & 0.47 (0.24–1.04) a & 0.35 (0.19–1.01) a & z = \(-\)3.40, \(p=0.001\) * \\ Group E & 0.36 (0.22–0.99) a & 1.69 (0.84–3.19) b & z = \(-\) 3.35, \(p=0.001\) * \\ Group F & 0.41 (0.18–0.87) a & 0.45 (0.23–1.02) a & z = \(-\)3.41, \(p=0.001\) * \\ \multicolumn{3}{c}{**H = 3.79, \(p=0.579\)} & \multicolumn{1}{c}{**H = 38.7, \(p<0.0001\) *} \\ \hline \end{tabular} Z; Wilcoxon test; * statistically significant; Different lower case within a column indicates significant difference between the groups (\(p<0.0001\), pairwise comparison using Mann-Whitney test); H; Kruskal-Wallis test; Group A—Opalescence17 PF; Group B—distilled water; Group C—thWhite Dark Stains Toothpaste; Group D—24 K white charcoal teeth–whitening pen; Group E—0.25% citric acid; Group F—thWhite Dark Stains Whitening Kit.  
\end{table} 
Table 2: Comparison of surface roughness (Ra) of within and between the study groups, at baseline and after treatment. Figure 1: Box plots of surface roughness (Ra) of the study groups at different measurement intervals.