## 4 Discussion
### Comparison between In-Office and At-Home Dental Bleaching
\begin{table}
\begin{tabular}{c c c c c} \hline
**Authors** & **Type of the Study** & **Aim of Study** & **Materials** & **Results** \\ \hline \multirow{6}{*}{[PERSON] et al., 2017 [50]} & \multirow{6}{*}{Randomized clinical trial} & Comparison between two techniques of in-office bleaching: 6\% of of HP. & Thirty patients. In-office bleaching in 2 modes: 1 application of 36 min versus 3 applications of 12 min, each for 2 sessions. & The combined protocol reduced the time \\  & & Comparison between at-home and in-office bleaching 10\% CP and 35\% HP. & 45 min with 35\% HP and at-home bleaching 10\% CP. & \\  & & & \\ \hline \multirow{6}{*}{[PERSON] et al., 2019 [55]} & \multirow{6}{*}{Randomized, controlled clinical trial} & Comparison between at-home and in-office bleaching & 45 min with 35\% HP and at-home bleaching \\  & & & 10\% CP and 35\% HP. & \\  & & & 10\% CP. & \\ \hline \multirow{6}{*}{[PERSON] et al., 2022 [56]} & \multirow{6}{*}{Randomized, controlled clinical trial} & \multirow{6}{*}{Comparison between at-home bleaching and in-office bleaching} & One-hundred participants divided into 4 groups: G1 35\% HP (4 sessions, 1 a week); G2 LED violet (4 sessions, 1 a week); G3 LED violet (4 sessions, 2 a week); G4 hybrid technique (LED violet + 35\% HP; 4 sessions, 1 a week). & The hybrid technique showed excellent bleaching with TS. \\  & & & \\ \hline \multirow{6}{*}{[PERSON] et al., 2021 [52]} & \multirow{6}{*}{Randomized, controlled clinical trial} & Comparison between in-office and at-home bleaching: 40\% HP, 16\% CP, and 10\% CP. & Sixty participants divided in 3 groups: 1. 40\% HP in-office, 2 home bleaching with 10\% CP compared to 16\% CP, 3 home bleaching with 10\% CP. & Same bleaching efficacy but with lower TS of home bleaching with 10\% CP, 16\% CP and in-office bleaching with 40\% HP. & The most effective protocol is low \\  & & & 10\% CP/ 1 h a day; (2) 10\% CP/  overnight; (3) 7.5\% HP/ 1 h a day; (4) 7.5\% HP/  overnight. & \\ \hline \multirow{6}{*}{[PERSON] et al., 2020 [17]} & \multirow{6}{*}{Randomized clinical trial} & \multirow{6}{*}{Comparison between bleaching with or without reservoirs with 10\% CP.} & Forty-six patients divided into 2 groups: 10\% HP once daily for 60 min to the buccal surface (BSB) and 10\% HP once daily for 60 min to the lingual surface (LSB). & The presence of reservoirs in a bleaching tray did not improve bleaching or determine TS and 60 min to the lingual surface (LSB). & The presence of reservoirs in a bleaching tray did not improve bleaching or determine TS and 60 min to the buccal surface (LSB) and 10\% HP once daily for 60 min to the lingual surface (LSB). & The presence of reservoirs in a bleaching tray did not improve bleaching or determine TS and 60 min to the lingual surface (LSB). & \\  & & & \\ \hline \end{tabular}
\end{table} 
Table 6: _Cont._  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline  & & & Thirty participants divided into two groups: 1. 15 received hybrid treatment in-office the most effective. \\ [PERSON]. 2019 [57] & Randomized, controlled trial & Comparison of at-home bleaching techniques 6\% HP and 16\% CP. & 1. 15 received hybrid treatment in-office bleaching (6\% HP + 2 weeks at-home bleaching with 16\% CP); 2. 15 in a control group. & The hybrid treatment is bleaching (6\% HP + 2 weeks at-home