## 4 Discussion
Future studies should compare the long-term outcomes of using reciprocating single-file systems in combination with matching gutta-percha points for obturation with regard to the healing rate of periapical lesions compared to other preparation and obturation techniques. The appropriate irrigation protocol, along with ultrasonic activation, can significantly impact these outcomes and should be carefully considered in this context [22; 32]. The size of the periapical lesion is also highlighted as a crucial factor, as its growth significantly reduces the success of endodontic therapy [33]. A previous study, which compares variable- and constant-tapered single-cone gutta-percha obturation systems, shows that the area filled with gutta-percha is larger with the lateral condensation and single-cone technique with constant-tapered gutta-percha than with variable single-cone gutta-percha (ProTaper(r), Reciproc(r), WaveOne(r)) [34]. In another study that compares WaveOne Gold and Reciproc(r) Blue, it was found that Reciproc(r) Blue demonstrated superior adaptation and achieved ideal filling conditions more frequently, especially at 1 mm from the root apex and in the lingual wall. Despite observing larger spaces in the WaveOne(r) Gold group, these variances did not reach statistical significance [35]. In our study, no significant differences were found between WaveOne(r) Gold, Reciproc(r) Blue, and Procedile in terms of PGFA, PSFA, and PUA in different areas of the root canal. Reciproc(r) Blue shows a slightly better percentage of gutta-percha filling in all areas and in both curved and straight canals. Among these three products, Wave One(r) Gold has the lowest PGFA apically (3 mm from the root apex) with 76%, but the greatest proportion of sealer with zero voids. A previous study indicated that Reciproc(r) Blue is more resistant to cyclic fatigue than WaveOne(r) [36, 37, 38]. In our study, no instrument fractures were detected in any of the single-file systems across all study periods. All three single-file systems demonstrated reliable methods for root canal preparation. This study adds to the understanding of single-file root canal preparations combined with single-cone obturation techniques, affirming their safety and efficacy in root canal treatment across all three manufacturers, although the limitations of an ex vivo study compared to a clinical study should be considered. Despite attempts at standardization, the diameter, the configuration of root canals, the anatomical variations, and the different tapers of the used single-file instrumentation systems and their corresponding gutta-percha cones can influence the results [39]. In order to minimize the influence of these anatomical variations and root canal configurations, roots with an initial apical file greater than size 15 were excluded in the present study. Furthermore, differences in dimensions between the file instruments and the cones should be taken into account [40]. Since in this study samples had to be discarded and replaced after evaluation under the microscope due to the canal configuration or anatomical variations like oval- or c-shaped canals, possible impacts on the results should be considered [41]. Despite the results of the present study, the clinical impact of the observed composition of single-cone root canal obturation on the outcome and healing of pulpal and periapical disease remains uncertain. Therefore, we propose clinical studies in prospective or at least retrospective design to evaluate different single-file systems in future studies [42]. The fact that the teeth were collected at different times, from various dentists, and without consistent consideration of the patients' ages may introduce uncontrolled variability that could affect the consistency and reproducibility of the results.