## 4 Discussion  
This ex vivo study intended to assess the influence of blood contamination on the push-out bond strength obtained with three different bioactive materials to root canal dentin. The ability to ensure a proper seal is one of the major requirements for root canal filling materials [5]. In many clinical applications, including vital pulp therapy, regenerative endodontic procedures, perforation and resorption repair, apical microsurgery, and apexification procedures, calcium silicate-based cements often undergo blood contamination even before completion of their setting reactions. Regardless of the context, adequate bond strength at the biomaterial-root canal dentin interface is crucial to withstand dislodgement forces during the immediate or delayed restorative procedures and resist masticatory forces. Among several currently available techniques, push-out bond strength testing is widely recognized as the most reliable method to assess the dislodgement resistance of materials to root dentin [28; 32]. [PERSON] et al. demonstrated that to apply the push-out test correctly, sample thickness should be greater than 1.10 mm, and the ratio between the plugger and filling material diameter should be no greater than 0.85. In our study, both recommendations were followed [30]. Furthermore, in the present study, bond strength testing was carried out considering the worst-case scenario since the load during testing was exerted in apical-coronal direction, therefore simulating an unfavorable root canal geometry. Thus, the risk that eventual mechanical retentions could lead to an overestimation of bond strength was minimized. The effectiveness of bonding to root canal dentin relies, among several factors, on the selected biomaterial. The initial seal obtained with bioactive materials is purely mechanical. However, subsequent biomineralization occurs at the biomaterial-dentin interface through hydroxyapatite crystals formation over time, providing it with chemical bonding [23; 33; 34; 35]. In the present experimental study, TotalFill presented statistically higher mean push-out bond strength values when compared with both Biodentine and MTA, which agrees with [PERSON] et al. [36]. A possible explanation relies on TotalFill's nanospheric size particles (maximum 1e-3 um) that promote, for the same volume of material, an increased surface area in contact with tissue fluids. Consequently, higher carbonated apatite precipitation is expected, with subsequent superior formation of tag-like structures [35]. The more favorable consistency and handling properties of TotalFill over the two remaining tested materials might also explain its superior results and contribute to greater outcome predictability. Moreover, statistically higher push-out bond strength was verified for Biodentine over MTA, which is in agreement with both [PERSON] et al. and [PERSON] et al. in their previous studies [25; 31]. The addition of calcium chloride to Biodentine's composition seems to act as a catalyst for tricalcium silicate hydration [17]. During hydration, small fibrous crystal formation occurs, which indicates rapid crystallization. This phenomenon might arise from the high ionic content of the solution when calcium chloride is present during tricalcium silicate setting and hardening, leading to the formation of heterogeneous density areas instead of a homogeneously dense structure. This facilitates the diffusion of ions and water through the initial calcium silicate layer, thus allowing a higher rate of hydration during the early diffusion-controlled period [37]. Additionally, the superior \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{3}{c}{**Fracture Pattern**} \\ \hline
**Experimental Group** & **Adhesive** & **Cohesive** & **Mixed** \\ \hline MTA/Blood & 39 & 0 & 6 \\ MTA/Saline & 42 & 0 & 3 \\ \hline Biodentine/Blood & 45 & 0 & 8 \\ Biodentine/Saline & 38 & 1 & 6 \\ \hline TotalFill/Blood & 43 & 0 & 2 \\ TotalFill/Saline & 37 & 0 & 8 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Fracture pattern analysis results.