## 4 Discussion
Additionally, the matched-taper SC technique avoids the spreaders' wedging pressures during the LC technique, which lowers fracture resistance [41]. Taking into account these details, the single-cone technique was employed in the current research. The anatomical variations, age, and timing of tooth extraction that may affect the findings make it difficult to standardize human teeth for evaluation of fracture strength [42]. It is important to standardize dimensions of the MD, BL, and root canal diameter and length of the extracted samples [43]. In our study, the BL and MD coronal plane diameters were measured using a digital caliper. The preparation size, root length, and root width were standardized for all teeth. Due to the evenly distributed stress in roots during filling, creating canals with a round cross-section reduces the risk of root fracture [44]. To accomplish this, rotary files were used for root canal preparation. Moreover, the testing device's parameters in this experiment were restricted to the physiological values reported in the literature [27]. Prior to loading, the specimens are exposed to thermal cycling between 5 and 55 \({}^{\circ}\)C according to ISO standardized bath temperature [45]. The forces that are generated by chewing or swallowing, which frequently range from 2 to 50 N Thus, a clinically relevant condition was approached using a cyclic loading force of 49 N [25]. To simulate bony sockets that may alter the force distributions around the teeth when external pressures like lateral compaction are used, many studies have replicated the periodontal ligament during root canal filling [46]. Elastomeric materials, according to [PERSON] et al. [46], are unable to react to compaction forces in the same way as normal ligament, which collapses under pressure. In the present experiment, after filling and before the thermal-mechanical cycling began, the roots were surrounded with a polyether impression material. This method tried to mimic the periodontal ligament, which effectively improves stress distribution during fatigue loading [47]. In the current study, the samples were decoronated at the cement-enamel junction in accordance with a prior study [48], for the sake of simplification and to eliminate the access cavity as a variable, the compressive load was applied directly to the root canal filling in this study [49]. The roots protruded 9 mm above the embedding substance. This is to mimic the clinical situation in which no 50% bone support is required for premolars to have a good periodontal prognosis if all other variables are favourable [50]. The present study revealed that thermomechanical aging resulted in statistically significant differences, BioRoot RCS showed decreased fracture resistance after different periods of aging, while AH Plus showed increased fracture resistance after a simulated 1 % years and then a dramatic reduction in fracture resistance after 3 years of aging. However, all different time periods of thermomechanical aging with BioRoot RCS showed significantly higher fracture resistance than AH Plus, in contrast with previous studies [51; 52; 53]. There may not have been any differences in VRF between BioRoot RCS and AH Plus in prior experiments because of the absence of fatigue stress. The increased fracture resistance of BioRoot RCS compared to AH Plus sealers may be caused by the fact that BioRoot RCS acquired lower flow and higher film thickness values than those recommended for AH Plus in ISO 6876 [54]. As BioRoot RCS has a low contact angle and is hydrophilic material, it should enable these sealers to penetrate the difficult aspects of the root canal more effectively [55]. Furthermore, zirconium oxide, one of the components of BioRoot RCS has properties that include high fracture resistance, high tensile strength, and a low Young modulus [56]. Calcium silicate sealers have a higher modulus of elasticity than epoxy resin-based sealers, which are closer to dentine, improving fracture resistance [36].