## 6 Discussion  
Endodontically treated teeth present high levels of structural destruction, which implies, in some cases, the rehabilitation with fiber posts and crowns. It has been observed that one of the main failures is the post-dislodging from the root canal, therefore, it is \begin{table}
\begin{tabular}{c c c c c} \hline
**Diodo Laser (MPa)** & **Nd: YAG (MPa)** & **Er: YAG (MPa)** & **PIPS (MPa)** & **Er, Cr: YSGG (MPa)** \\ \hline \multicolumn{5}{c}{**Cervical**} \\ \hline
5.25 [(17)] & 6.15–13.14 [(17; 28)] & 6.54 [(17)] & 8.40–17.7 [(17; 41)] & 5.02 [(49)] \\ \hline \multicolumn{5}{c}{**Middle**} \\ \hline N/D & 12.28 [(17; 28)] & N/D & 16.7 [(41)] & 5.38 [(49)] \\ \hline \multicolumn{5}{c}{**Apical**} \\ \hline
4.62 [(17)] & 5.03–9.47 [(17; 28)] & 5.04 [(17)] & 6.21 [(17)] & 4.03 [(49)] \\ \hline \multicolumn{5}{c}{**Mean**} \\ \hline
4.94 [(17)] & 5.59–11.63 [(17; 28)] & 5.79 [(17)] & 7.31 [(17)] & N/D \\ \hline \end{tabular}
\end{table} 
Table 4: Range of results of POBS analysis in fiber posts applied in dentin treated with different lasers to activated NaOCI, ethylenediamenettraacetic acid (EDTA), MTAD, and 5.25% NaCl + 17% EDTA. (N/D: no data). \begin{table}
\begin{tabular}{c c c} \hline
**Er.Cr. YSGG (MPa)** & **Er.YAG (MPa)** & **Diode Laser (MPa)** \\ \hline \multicolumn{3}{c}{**Cervical**} \\ \hline
1 W–2 W = 15.17 [(69)] & N/D & 5.72 [(27)] \\ \hline \multicolumn{3}{c}{**Middle**} \\ \hline
1 W–2 W = 10.86 [(69)] & N/D & 3.37 [(27)] \\ \hline \multicolumn{3}{c}{**Apical**} \\ \hline
1 W–2 W = 12.20 [(69)] & N/D & N/D \\ \hline \multicolumn{3}{c}{**Mean**} \\ \hline
1 W–2 W = 4.86–12.72 [(29; 69)] & 3.90–9.91 [(29; 68)] & 4.61 [(27)] \\ \hline \end{tabular}
\end{table} 
Table 5: Range of results of POBS tests of fiber posts in dentin irradiated by different lasers and output power. W: Watts; N/D: no data. extremely important to perform pre-treatment of the root dentin with several conditioning techniques that allow the infiltration of the adhesive monomers into the dentinal tubules. Interestingly, irrigation of 17% EDTA during 20 s promoted higher bond strengths [10]. However, increasing time > 1 min leads to dentin erosion [11], thus, the time factor is critical for maintaining of the dentin structure. On the other hand, combination of EDTA with 5.25% NaCl facilitates SSL elimination from the root canal [11, 27], but NaCl followed by EDTA can produce great erosion of dentin [39], since NaOCl decomposes into sodium chloride and oxygen. The release of oxygen inhibits the polymerization of resinous adhesive materials, which interferes with the infiltration of resin in the demineralized dentinal tubules, creating a greater probability of debonding of the post from the root canal [10, 27, 71]. Another conditioning with a high impact on dentin is OA, which demineralizes inter- and peritubular dentin [72], and its etching capacity depends on its ability to fully infiltrate root dentin irregularities [30]. Several difficulties have been described with the use of this conditioning due to its presentation since it can be found in liquid and gel forms. The gel form enhances dentin conditioning due to its viscosity promoting adhesion of the post. Also, this form allows a better control of its application [30, 73]. However, it has been shown that the OA in the gel cannot be thoroughly eliminated in the apical third, influencing cement adhesion [50], unlike the liquid form, which allows deeper penetration and leads to an improvement in the acidic conditioning due to its lower viscosity, higher wettability, and lower surface energy compared to the gel form [28, 73]. Despite the abovementioned, the liquid form with sonic activation promotes better adhesion to fiberglass posts to root canals compared to the gel form [30]. Interestingly, sonic devices present some advantage such as they do not cause involuntary removal of dentin by their plastic tips [58], however, some sonic devices operate on low power [74].