## 4 Discussion  
This study evaluated the incidence of debris and open dental tubules after irrigation with mechanical activators (XPE, XPC, or EC) compared to PUI and their effects on the adhesive interface. Based on the results, the tested hypotheses (H01 and H02) were rejected because there were significant differences both between the agitation methods regarding the incidence of debris and the quantity of open dental tubules in the apical third, and in the bond strength of the hydraulic calcium silicate-based sealer to dentin after 6 months, respectively. The importance of irrigation solution activation to enhance cleaning and minimize debris in the root canal is well established [27; 28; 29]. It is well known that hard tissue debris generated during mechanical instrumentation can compact into the irregular canal configurations, leading to reinfection by debris containing bacteria [30]. Additionally, it is important to understand that the root canal preparation and obturation complement each other, with the preparation stage being fundamental to the success and longevity of obturation [31]. Figure 4: Failure modes after the push out test as a function of the mechanized final irrigation protocol and root third (ecervical, middle, and apical) at 6 months of evaluation. XPE, XP-Endo Finisher; XPC, XP-Clean; ECL, Easy Clean; PUI, passive ultrasonic irrigation. The results regarding the incidence of debris and open dentinal tubules obtained in this study at the end of each final protocol of mechanized irrigation showed that the debris removal capacity was similar for all groups, except in the apical third, where Easy Clean with a reciprocating motion was less efficient (Figure 2). This may have occurred due to the protocol used. It is known that Easy Clean is an instrument composed of polymers that allows for reciprocal movement during sodium hypochlorite activation [32]. However, it is believed that using the instrument in rotary kinematics may be more effective [33]. Ideally, insolubility is the primary prerequisite for a root canal sealer to offer a perfect sealing capacity, along with good mechanical properties [34]. Therefore, a high degree of solubility could consistently allow for the creation of gaps within and between the material and the dentin canal wall [35]. Calcium silicate-based bioceramic sealers generally exhibit higher solubility when compared to polymer-based materials, owing to the material's chemical components [33]. Furthermore, the prolonged setting time of an automix hydraulic calcium-silicate based sealer poses a significant clinical challenge. A lengthy setting time can lead to clinical issues due to the sealer's inability to maintain shape and withstand stresses during this period [36]. The majority of hydration in hydraulic calcium silicate-based sealer occurs within the first few weeks, although complete hydration may take up to 1 or 2 years [36]. Therefore, it is speculated that the setting time issue of the material, combined with its solubility, may have contributed to a significant reduction in the bond strength of the hydraulic sealer (Bio-C Sealer) to dentin when comparing the different evaluation times in this study (6 months vs. 48 h), regardless of the root third, within the same final irrigation protocol. Additionally, debris in dentin obstructs dentinal tubules, preventing sealer penetration into the dentinal tubules of the root canal [37]. This explains why the ECL protocol exhibited lower bond strength between the hydraulic calcium silicate-based sealer and root canal dentin in the apical root third after 48 h and at 6 months of evaluation. When evaluating the failure pattern, this study demonstrated that both at 48 h and at 6 months, mixed failure was most frequent in the cervical and middle thirds of the root canal, regardless of the final irrigation protocol used. This suggests that failure occurred at the interface between sealer, gutta-percha cone, and root dentin, possibly due to the solubility of the obturation material over time, compromising its covalent bonds [38].