## 4 Discussion  
This study protocol aimed to determine the time-dependent effects of EDTA on the fracture strength of the tooth. In addition, the chemical interactions formed during the procedures were also considered for the design of the study hypothesis, and all possible clinical variations were included in the cause-effect relationship to be obtained, such as with or without CH dressing. The null hypothesis of this study focused on the possibility that the solution may passivate by the presence of CH and may require a longer time to affect the dentin surface; the null hypothesis was partially accepted based on the CH group's statistical analysis. For this study, mandibular premolar teeth were preferred due to their high exposure to functional chewing forces in the oral cavity [29; 30]. Premolar teeth are exposed to more vertical than lateral forces during function so a load was applied vertically to the model to simulate occlusal forces [31]. [PERSON] et al. reported that lower tapered preparation strengthens the fracture resistance of the mandibular premolar tooth and emphasizes the loss of pericervical dentine structure [32]. Coronal preflaring is necessary to enable clear access into the middle and apical thirds of root regions, facilitate irrigation solution circulation, and allow subsequent engine-driven endodontic files to prepare the apical section with less frictional force; however, it causes lead dentinal defects [33]. Although the teeth were decorated without coronal preflaring and the preparation of root canals was as minimally invasive as possible (by using a 0.04 tapered file system) in this study, it should be mentioned that root canal preparation decreased the root resistance of fracture, based on the study results. Compared to previous reports [1; 5; 6; 34], when the results of this study were evaluated in general, it was observed that the highest fracture resistance belonged to the group which had not undergone any treatment procedure. Therefore, it is imperative to emphasize maintaining tooth vitality if possible and avoiding unnecessary root canal treatment in teeth that is not indicated. Cholation agents support the irrigation process but may cause physicochemical changes on dentin tissue, such as roughness, microhardness, and surface structure [35; 36; 37]. Although the increase in surface roughness achieved in endodontic procedures may provide clinical benefits in terms of micromechanical bonding of obturation materials to root dentin, the microhardness of dentin and the mineral composition changes may affect the resistance of the root structure against such forces [5; 38]. The effects of agents on dentin have been evaluated by various types of experimental studies in vitro [21; 22; 27; 28; 35; 36; 38]; however, it may be stated that the primarily interpretive contribution of our research to clinical practice is its evaluation of the effects on tooth resistance and strength. Therefore, this study aimed to examine the impact of chelator agents with activation on the dentin surface in the best way possible to mimic clinical impact, i.e., via fracture resistance tests. However, although the CH group had the lowest fracture resistance compared to the other groups, no significant difference was found in EDTA application times when the groups with and without CH application were evaluated individually. [PERSON] et al. evaluated the effectiveness of applying 17% EDTA solution for different periods (1, 3, 5, and 7 min) in terms of removing the smear layer. They observed that a 1-min EDTA application was insufficient to remove it completely. However, 7 min of EDTA exposure successfully removed the smear layer with a minimal change on the dentin surface [39]. According to the present results, although no statistically significant difference was found among the 1, 3, and 5-min EDTA application groups on the non-subjected CH group, the raw values indicated a tendency for fracture resistance to increase up to 5 min.