# Effect of Endodontic Irrigation on the Bond Strength of Composite Restoration Repair
## 4 Discussion  
Repair of composite fillings is theoretically valid and increasingly accepted as a conservative option. A clinical study by [PERSON] et al. [18] reported a favorable prognosis for repaired fillings. In the temporary absence of evidence-based guidelines, the decision to repair rather than replace should be based on the patient's individual risk of caries, a professional assessment of benefits and risks, and consideration of conservative principles in cavity preparation [19; 20]. [PERSON] et al. [21] reported, in their meta-analysis, that chemical or physical-chemical surface treatments of aged dental composites were beneficial for improving the repair bond strength of methacrylate-based restoratives. However, to the best of our knowledge, there is no study in the literature on how composite materials change as a result of contact with endodontic irrigation solution or how this affects bonding strength. Therefore, the aim of this study was to investigate the effects of different sequential solutions (NaOCI, EDTA, CHX) used in root canal treatment on the restoration of composite material with composite again. In the present study, intermediate bonding was applied. In a study comparing different etching and adhesive application protocols, the lowest bond strength was observed in the control group where intermediate bonding was not applied [22]. As monomers in bonding agents penetrate into the composite filling, oxygen is blocked and a non-polymerized layer is formed, allowing new layers to bond. In addition, intermediate adhesive resins show affinity to inorganic fillers by bonding with hydrogen and silane [23]. Although \begin{table}
\begin{tabular}{c c c c c c} \hline  & \multicolumn{5}{c}{**Solutions**} \\ \cline{2-6}  & **Control** & **NaOCI** & **NaOCI + EDTA** & **NaOCI + CHX** & **NaOCI + CHX** \\ \hline
**Aged** & 24.81 \(\pm\) 5.56 \({}^{\text{A}}\) & 15.3 \(\pm\) 4.56 \({}^{\text{B}}\) & 23.31 \(\pm\) 5.12 \({}^{\text{A}}\) & 21.25 \(\pm\) 5.63 \({}^{\text{A}}\) & 21.08 \(\pm\) 4.42 \({}^{\text{A}}\) \\
**Non-aged** & 23.05 \(\pm\) 3.62 \({}^{\text{A}}\) & 15.53 \(\pm\) 4.44 \({}^{\text{B}}\) & 21.36 \(\pm\) 5.32 \({}^{\text{A}}\) & 21.27 \(\pm\) 4.21 \({}^{\text{A}}\) & 20.09 \(\pm\) 4.03 \({}^{\text{A}}\) \\ \hline \end{tabular}
\end{table} 
Table 2: Means and standard deviations of the shear bond strength (MPa) test (\(n\) = 18). \begin{table}
\begin{tabular}{c c c c c c} \hline  & **Adhesive** & \begin{tabular}{c} **Cohesive** \\ **(Restorative)** \\ \end{tabular} & \begin{tabular}{c} **Cohesive** \\ **(Repair)** \\ \end{tabular} & \
\begin{tabular}{c} **Mixed** \\ **(50\% Restorative)** \\ \end{tabular} &
\begin{tabular}{c} **Mixed** \\ **(50\% Repair)** \\ \end{tabular} \\ \hline
**Control (aged)** & - & 33.3 & - & 55.5 & 11.1 \\
**Control (non-aged)** & - & 38.8 & - & 61.1 & - \\
**NaOCI (aged)** & 5.5 & 22.2 & - & 55.5 & 16.6 \\
**NaOCI (non-aged)** & - & 27.7 & - & 66.6 & 5.5 \\
**NaOCI + EDTA (aged)** & - & 33.3 & - & 61.1 & 5.5 \\
**NaOCI + EDTA (non-aged)** & - & 33.3 & - & 66.6 & - \\
**NaOCI + EDTA + CHX (aged)** & - & 50 & - & 38.8 & 11.1 \\
**NaOCI + EDTA + CHX (non-aged)** & - & 44.4 & - & 44.4 & 11.1 \\
**NaOCI + CHX (aged)** & - & 38.8 & - & 61.1 & - \\
**NaOCI + CHX (non-aged)** & - & 27.7 & - & 66.6 & 5.5 \\ \hline \end{tabular}
\end{table} 
Table 3: Mode of failure after the shear bond strength test (%). previous studies have reported variable bonding strength outcomes depending on the type of adhesive systems used for composite repair, only one adhesive system was intentionally used in the present study. This was because the primary objective was not to compare different adhesive systems but, rather, to investigate the influence of endodontic irrigation solutions on composite-to-composite bond strength. Therefore, the use of a single adhesive system helped to isolate the effects of irrigation variables and avoid confounding results.