## 4 Discussion
This situation may be explained by the fact that the smear layer is removed more effectively as the EDTA application time increases by up to 5 min. Consequently, the filling materials bond better to the dentin walls. The duration of intracanal medication application varies depending on the reason for its use. While this period is shorter for canal disinfection between appointments, it can take up to 11 weeks for apexification or regenerative treatments [40]. In routine endodontic treatment, it is known that CH shows its effect in 1-4 weeks [41]. In thisstudy, the CH-placed samples were kept in an incubator (37 \({}^{\circ}\)C and 100% humidity) for one week, representing the time between two appointments in the oral environment for the most effective minimum duration. [PERSON] et al. stated that CH causes significant collagen degradation in superficial root dentin, even after only one week of application [42]. Collagen is responsible for hard tissue durability, and prolonging the residence time of CH in the root canal reduces the fracture resistance of the tooth [43,44]. In this study, the fracture resistance of the CH-applied group was found to be statistically significantly lower compared to the fracture resistance of the non-subjected CH group. Therefore, it can be stated that CH affects the structure of dentin, even in a short time. Resistance decreased the root structure after root canal preparation, but it can be strengthened after obturation [45]. Gutta-percha and root canal sealers are the most commonly used filling materials for root canal obturation. However, the elastic modulus of gutta percha is very low compared to dentin. On the other hand, root canal sealers increase resistance to fracture by bonding to the dentin surface and strengthening the remaining tooth structure [46,47]. This situation can be explained by the effective penetration of the sealer into the dental tubules and its ability to bind to the root dentin [45]. Various types of root canal sealers are used for root canal treatment. Epoxy resin-based root canal filling pastes are widely used for obturation due to the lack of polymerization shrinkage, good adhesion abilities, and antimicrobial properties [48]. In this context, in this study, warm obturation was applied with a resin-based root canal sealer to prevent the material from being negatively affected by temperature and to increase its fluidity. Additionally, the root canal obturation material was allowed two weeks to harden entirely before the fracture test. The authors think that possible CH residues that could not completely be removed from the root canal may have continued to affect the dentin structure, as well as the durability of the tooth. Unfortunately, this is also a fact of an unpredictable and inevitable clinical condition. Beyond its erosive effect on dentin, EDTA also affects the removal of the smear layer and CH. Such multifactorial conditions within the root canal system may have contributed to the lack of statistically significant differences observed in this study. Additionally, as the duration of EDTA usage increases up to a certain point, it effectively removes the smear layer. This situation can enhance the penetration of the obturation material into the dentin tubules, increasing the tooth's fracture resistance. Due to the multifactorial nature of fracture resistance, its evaluation can be challenging. Therefore, it is recommended that future studies correlate fracture resistance with factors such as dentin penetration, the presence of the smear layer, and the remaining CH. In the results of [PERSON] et al., no statistically significant difference was found in the smear removal efficacy between the 3 and 5-min EDTA application groups. Additionally, they found no statistical difference in the degree of erosion on the dentin surface with 1, 3, 5, and 7 min of application [39]. The lack of a significant difference in our results when associating fracture resistance with dentin erosion and residual smear layer appears consistent with this study.