## 4 Discussion  
According to the results of our study, the highest MPD values were observed in the SWEEPS groups, while the lowest value was in the CSI groups. Considering the sealer type and irrigation protocol interaction effect, there was a significant difference between the Er,Cr:YSGG laser and EA groups for the AHPB sealer, while it was insignificant for the AHP sealer. The penetration percentage values were affected by the tested variables, but the interactions between the variables were insignificant except for irrigation technique * root third interaction. However, the novel AHPB sealer is a recently introduced root canal sealer for endodontic use. Generally, the biocompatibility and bioactive properties of bioceramic sealers are superior in addition to their ability to encourage a surface layer of hydroxyapatite, which could generate a mineral attachment to dentin tissue [20; 21]. However, the extent to which root canal sealers are capable of effectively sealing the root canal is influenced by many factors, including penetration of the sealer into dentin tubules, the canal irrigation technique used for smear layer removal, and the type of sealer [22; 23]. Thus, this research aimed to assess the depth and percentage of the novel AHPB sealer compared to the traditional AHP sealer into dental tubules subsequent to different irrigation activation protocols using CLSM. Researchers have previously used CLSM and scanning electron microscopy (SEM) devices to evaluate the extent to which sealers are capable of penetrating into dentin tubules [22; 24]. In this study, it was preferred to use CLSM due to its superior evaluation properties compared to SEM. A desiccation process should be applied to root sections for SEM evaluation, which may result in sealer being lost and the specimen and materials being deformed [25]. In addition, a detailed image of the specimen and a quick evaluation of the sealer penetration can be acquired at a lower magnification by CLSM using fluorescent rhodamine B dye without changing the flow characteristics of the sealers [26; 27]. To minimize the presence of anatomical irregularities and apical delta, which could impact the penetration of the sealer, sample sections were chosen to be taken from 3 and 6 mm distances from the apex in this study, similar to previous studies [22; 28]. However, in agreement with other papers [29; 30], our results stated that for both sealers, the sealer penetration values (depth and percentage) in all the irrigation protocol groups were higher in the middle third in comparison to the apical third. These anticipated outcomes could arise from the larger diameter and higher density of the dentinal tubules in the middle region compared to those in the apical area. Furthermore, the task of eliminating the smear layer in the apical third poses greater difficulty, primarily because effectively delivering irrigation solutions to that particular area is more complex and demanding. [31]. In the current study, irrigation solutions including NaCl and EDTA were used with different methods of activation for removing the smear layer, which is essential to ensuring that the root canal sealer penetrates the dentinal tubules at a high rate, increasing the sealing ability, and decreasing microbial microleakage [2; 32]. According to this study's findings, significant differences were detected between all the irrigation protocol groups regarding MPD, where the order from the highest to the lowest values was as follows: SWEEPS > Er,Cr:YSGG > EA > PUI > CSI. As expected, the CSI group showed the lowest depth and percentage of sealer penetration in comparison to the other groups, in line with the findings of past research [33; 34].