## 4 Discussion
An explanation of this finding could be that when the CSI method was used, the irrigant reached no further than 2 mm from tip of the needle, meaning that it was incapable of reaching irregularities and the canal's apical region [35], although it has been stated in other studies that significant differences did not exist between CSI and other irrigation activation techniques [36]. However, [PERSON] et al. [11] noted that SWEEPS enhances the capacity for debris and smear layer removal. This technique can produce bubbles by activating the Er:YAG laser via the photoacoustic streaming effect. When these bubbles collapse, they generate an intensely swift irrigant jet adjacent to the canal walls, significantly amplifying surface cleaning through acoustic streaming. According to the findings of the study by [PERSON] et al. [37], the Er:YAG laser methodpresented the greatest efficiency in terms of removing the smear layer, irrespective of which solution was employed. Our findings indicated that the sealer MPD of the Er.Cr:YSGG laser was higher in comparison to that of PUI, EA, and CSI but lower than that of SWEEPS. This phenomenon might occur because the laser's energy absorption by the irrigant leads to the formation of vapor bubbles. These bubbles act as a fluid pump inside the root canal, creating a cavitation effect. Consequently, this process efficiently eliminates the smear layer and facilitates the infiltration of the irrigation solution into the dentinal tubules [38,39]. [PERSON] et al. [7] showed that Er.Cr:YSGG had increased effectiveness compared to PUI in improving the antibacterial effect of NaOCl. Conversely, it was demonstrated in another study that SWEEPS was not capable of increasing the sealer penetration compared to PUI [22]. The differences in these study findings could be associated with the utilization of distinct root canal sealer types in these studies that have various properties. Considering the penetration percentage, significant differences were detected among all the irrigation activation protocol groups except for the difference between the SWEEPS and Er.Cr:YSGG groups. Nevertheless, as aforementioned, the laser-activated irrigation showed higher activity in terms of cleaning the root canal and removing the smear layer compared with the alternative methods of irrigation. Interestingly, the EA groups showed a significantly higher sealer penetration depth and percentage than the PUI groups for both sealers used in this research, although it was confirmed by recent reports [40,41]. This may possibly be because of the short period of ultrasonic activation and the PUI file and the walls of the canal coming into contact. Furthermore, a downside of PUI was observed in terms of the reduction in its distinctive nodes and antinodes pattern, notably when the instrument made contact with the shaped canal's lateral walls. Sonic activation functioned with one positive and one negative node. The vibratory sonic tool's movement was not altered by contact with the lateral wall [42]. Considering the sealer type and irrigation protocol interaction, a statistically significant difference was found between the Er.Cr:YSGG laser and EA groups for the AHPB sealer, while it was insignificant for the AHP sealer. However, regardless of the irrigation activation protocol, the AHP and AHPB sealers statistically presented similar penetration properties. Although recent studies have reported that the AHPB sealer showed superior properties compared to AHP [16,43], our results presented insignificant differences between them in terms of dentin tubule penetration. [PERSON] et al. [17] compared AHPB to AH-Plus Jet and EndoSequence BC sealers and stated that the bioceramic-based root canal sealers seemed to exhibit superior performance compared with the epoxy-resin-based sealer with respect to the extent to which they penetrated the dentinal tubules, which was inconsistent with our findings. In their study, [PERSON] et al. [43] noted that AHPB had a shorter initial setting time and was less radiopaque than AHP.