## 2 Materials and Methods
### Statistical Analysis  
Statistical analyses were performed using SPSS version 21. Descriptive statistics for each variable were computed and expressed as \"Mean \(\pm\) Standard Error of Mean (SEM)\". Subsequently, a two-factor mixed-design ANOVA (analysis of variance) was employed using the General Linear Model procedure for repeated measurements. The model incorporated \"Group\" and \"Time\" as the primary effects, along with their interaction term (Group*Time). In instances where [PERSON]'s test indicated a violation of the assumption of sphericity, the Greenhouse-Geisser adjustment was implemented. To further dissect any significant interaction effect terms as a post hoc analysis, a simple effect analysis with Sidak  
Figure 1: Schematic representation of the experimental setup.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & **Time:** & **T0** & **T1** & **T2** & **T3** & **T4** & **_P_ & \\ \hline
**Group** & \(n\) & \(Mean\in Sd\) & \(Mean\in Sd\) & \(Mean\in Sd\) & \(Mean\in Sd\) & \(Mean\in Sd\) & _Group_ & _Time_ & _Group\({}^{\star}\)Time_ \\ \hline No bonding, no laser & 10 & 9.97 \(\pm\) 1.95  & 9.76 \(\pm\) 0.75  & \(\Delta\)\({}^{*}\) & \\ Optiboond FL & 10 & 7.37 \(\pm\) 0.95  & 8.21 \(\pm\) 0.53  & \\ \cline{1-1} Bond & 10 & 10.27 \(\pm\) 1.02  & 12.83 \(\pm\) 1.16 [FOOTNOTE:]Footnote : footnotemark: [ENDFOOTNOTE] & 11.34 \  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & **Time:** & **T0** & **T1** & **T2** & **T3** & **T4** & \(p\) & \\ \hline  & & & & & \(\Delta\)**L\({}^{*}\)** & & & & \\
**Group** & \(n\) & **Mean \(\pm\) St** & **Mean \(\pm\) St** & **Mean \(\pm\) St** & **Mean \(\pm\) St** & **Mean \(\pm\) St** & **Mean \(\pm\) St** & **Group** & **Time** & **Group\({}^{*}\)Time** \\ \hline b* & & & & & & & & & \\ \hline No bonding, no laser & 10 & 41.86 \(\pm\) 1.36 \({}^{\rm\AA}\) & 29.83 \(\pm\) 2.28 \({}^{\rm\AA}\), & 27.98 \(\pm\) 1.94 \({}^{\rm\AA}\), & 25.56 \(\pm\) 1.12 \({}^{\rm\AA}\), & 26.79 \(\pm\) 0.98 \({}^{\rm\AA}\), & & & \\ Optibor FD, & 10 & 44.81 \(\pm\) 1.76 \({}^{\rm\AA}\) & 30.56 \(\pm\) 2.51 \({}^{\rm\AA}\), & 30.18 \(\pm\) 1.07 \({}^{\rm\AA}\) & 29.61 \(\pm\) 1.06 \({}^{\rm\AA}\), & 28.17 \(\pm\) 1.23 \({}^{\rm\AA}\), & & \\ Clearfil SE Bond & 10 & 40.06 \(\pm\) 1.72 \({}^{\rm\AA}\) & 27.36 \(\pm\) 1.29 \({}^{\rm\AA}\) & 27.34 \(\pm\) 1.45 \({}^{\rm\AA}\), & 26.14 \(\pm\) 1.37 \({}^{\rm\AA}\) & 25.99 \(\pm\) 1.28 \({}^{\rm\AA}\), & 0.315 & \(<\)0.001 & 0.644 \\ Optibor Universal & 10 & 45.51 \(\pm\) 1.41 \({}^{\rm\AA}\) & 29.4 \(\pm\) 1.56 \({}^{\rm\AA}\) & 28.12 \(\pm\) 1.74 \({}^{\rm\AA}\) & 29.56 \(\pm\) 1.43 \({}^{\rm\AA}\), & 27.89 \(\pm\) 1.74 \({}^{\rm\AA}\) & & \\ Nd YAG Laser & 10 & 41.68 \(\pm\) 1.65 \({}^{\rm\AA}\) & 30.53 \(\pm\) 1.94 \({}^{\rm\AA}\), & 28.43 \(\pm\) 1.41 \({}^{\rm\AA}\), & 29.34 \(\pm\) 1.58 \({}^{\rm\AA}\) & 26.49 \(\pm\) 1.8 \({}^{\rm\AA}\) & & \\ \hline \end{tabular}  
* To: Day to Ti: 1 st Week, 21 st Month, Ti: 3 rd Month, Ti: 6 th Month, \({}^{\rm\AA}\), different letters in the same column show statistical significance (\(p<0.6\)), \({}^{\rm\AA}\), different letters in the same row show statistical significance (\(p<0.6\)).  
The results indicate that the degree of coloration increased with time within each group, with statistically significant differences observed among the groups in terms of the extent of discoloration (\(p<0.05\)). The highest degree of discoloration in each experimental group was observed at the end of the 6 th month, as compared to the 1 st month, except the Clearfil SE Bond group (\(p<0.05\)). On the other hand, no significant differences were observed between Optibond FL and Optibond Universal within each time interval, or between Clearfill SE Bond and the control group (\(p>0.05\)). When compared to the control group, the Nd YAG group exhibited the least degree of discoloration in all time intervals (\(p<0.05\)).