## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Multiple Comparisons of Bleaching Groups**} \\ \hline \multirow{2}{*}{**Bleaching Agent (A\({}_{1}\))**} & \multirow{2}{*}{**Bleaching Comparison Group (A\({}_{2}\))**} & \multirow{2}{*}{**Difference of Means (A\({}_{1}-A\))**} & \multirow{2}{*}{**Typical Error**} & \multirow{2}{*}{_p-Value_} & **95\% Confidence Interval** \\ \cline{3-3} \cline{5-6}  & SP & **32.64** & & & **Lower Limit** & **Upper Limit** \\ \hline \multirow{2}{*}{HP 30\%} & SP & **32.64** & 37.59 & \textless{}_0.001_ & 234.02 & 419.66 \\  & HP 30\% + SP & **152.173** & 44.81 & _0.004_ & 43.92 & 260.42 \\ \hline \multirow{2}{*}{SP} & HP 30\% & \(-\)**326.84** & 37.59 & \textless{}_0.001_ & 419.66 & \textasci{}234.02 \\  & HP 30\% + SP & \(-\)**174.67** & 24.43 & \textless{}_0.001_ & 234.99 & \textasci{}114.35 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of the results obtained between the different bleaching groups with the Games–H Howell contrast test after 10 days. that internal bleaching and trauma are the main predisposing factors for its appearance. Although the mechanism for this effect is still unclear, these studies support the idea that the bleaching agent or products derived from it reach the periodontal tissue through the dentinal tubules, initiating an inflammatory process. Therefore, quality restorations are important even though they are temporary. In non-vital bleaching, restorations are generally made with the same materials that are used for provisional restorations in endodontics to temporarily seal the tooth and prevent the loss of medication [40; 41; 42]. In the walking bleach technique, the aim is to avoid loss of the bleaching agent. However, the oxygen expansion reaction that occurs inside the chamber with the bleaching agents must be taken into account. Consequently, it would be reasonable to perform the provisional sealing with composite resin material and adhesives to ensure efficacy, so as to avoid bacterial leakage into the tooth and to prevent the bleaching agent from coming into contact with the oral tissues, since at high concentrations reactive oxygen radicals can cause genotoxicity and cytotoxicity [33; 43]. Care must be taken in choosing the proper temporary materials for the walking bleach technique. [PERSON] et al. already reported that the walking bleach technique requires a solid seal around the access cavity using a restorative composite to ensure its effectiveness and to avoid the aforementioned leaks, which cannot be guaranteed if endodontic provisional restorative materials are used. The clinical choice of a coronal temporary restorative material is of paramount importance to achieve a hermetic seal and for the success of the whitening treatment [33; 44]. Furthermore, temporary coronal restorative materials in endodontics are not indicated for periods of time longer than 1-2 weeks. In a previous study, gas expansion due to the bleaching agent was observed after 10 days [41]. [PERSON] et al. conducted an in vitro study with the aim of evaluating the effects of bleaching agents on the microleakage of coronal access restorations, observing microleakage in all groups except the control group [27]. The observations made in the current study coincide with and justify the results obtained by [PERSON] et al. [PERSON] et al. demonstrated the influence of a temporary adhesive restoration on the effectiveness of the whitening reaction with the walking bleach technique compared to a temporary \"mechanical retention\" filling, which is usually achieved with coronal temporary endodontic materials [44]. \"Mechanical retention\" cannot prevent oxygen leakage, which forces the patient to perform more sessions and increases the risk of complications.