## 4 Discussion
### Bleaching with Hydrogen Peroxide
The use of LED/Laser irradiation on in-office dental bleaching did not show better results compared with the technique without a light source but seemed to give an advantage in the TS and in the activation time [33] (Figure 2). Several studies point out the use of in-office 6% HP gel with nitrogen titanium dioxide (TiO\({}_{2}\)) nanoparticles activated by LED/Laser source as efficient for dental bleaching. [PERSON] et al. reported that there were no differences in the efficacy of a single application of 72 min of 6% HP with nitrogen TiO\({}_{2}\) nanoparticles or two applications of 36 min [34] (Table 4). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Authors** & **Type of the Study** & **Aim of the Study** & **Materials** & **Results** \\ \hline [PERSON] et al., 2020 & Randomized and prospective & To compare the change, stability of color and effects on & Patients (n = 25) were assessed at 12 months post bleaching treatment: 6\% HP & The effect of 37.5\% HP was significantly better than that of 6\% HP in terms of color rebound after 1 year of follow-up. The 6\% HP achieved a positive psychosocial impact and enhanced self-perception at follow-up. \\ \hline  & & To evaluate the bleaching effectiveness and the physicochemical effects on enamel of violet light and ozone, light and ozone, associate or not to HP, compared to 35\%-hydrogen peroxide. & Patients (n = 15): HP 35\%, violet light, ozone, the association between hydrogen peroxide with ozone or violet light. & Violet light associate with HP was unable to improve the color changes observed for the peroxide alone, combination with ozone and HP. \\ Tavares N.R.N.O. & Clinical trial & Clinical trial & All protocols were performed in two sessions with a 48 h & Violet light associate with HP was unable to improve the color changes observed for the peroxide alone, in combination with ozone and HP. \\  & & & & \\ Tavares N.R.N.O. & Clinical trial & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\ \end{tabular}
\end{table} 
Table 4: Reported studies about bleaching with hydrogen peroxide [HP: hydrogen peroxide, IL: interleukin, TS: tooth sensitivity]. Figure 2: The use of LED/Laser irradiation on in-office dental bleaching. \begin{table}
\begin{tabular}{c c c c c} \hline
**Authors** & **Type of the Study** & **Aim of the Study** & **Materials** & **Results** \\ \hline [PERSON] et al., 2017 [21] & Clinical trial & To evaluate the effect of surface treatments and waiting time prior to contact with dye on bleached enamel staining susceptibility. & Patients (n: 100): bleached with 35\% were in contact with red wine. & Surface treatments and waiting time were not significant to decrease bleached enamel \\ [PERSON] et al., 2017 [21] & Clinical trial & To evaluate the risk for and intensity of TS and color change of at-home dental bleaching with 4\% and 10\% HP. & \\ [PERSON] et al., 2018 [22] & Randomized, triple-blind clinical trial & To evaluate the risk for and intensity of TS and color change of at-home dental bleaching with 4\% and 10\% HP. & \\ [PERSON] et al., 2018 [22] & Randomized, triple-blind clinical trial & To evaluate the risk for and intensity of TS and color change of at-home dental bleaching with 4\% and 10\% HP. & \\ [PERSON] et al., 2018 [22] & Randomized, triple-blind clinical trial & To evaluate the risk for and intensity of TS and color change of at-home dental bleaching with 4\% and 10\% HP. & \\ [PERSON] et al., 2018 [22] & Randomized, triple-blind clinical trial & To evaluate the impact of 10\% hydrogen peroxide whitening & Patients (n = 113) were divided into: group 1 or control (n = 53), non-whitening strip exposed, and group 2 (n = 60), whitening strip exposed & Individuals exposed to 10\% hydrogen peroxide whitening strips exhibit NAs increased in oral epithelial cells and 8-OHdG in saliva.