## 4 Discussion  
This study aimed to assess changes in root canal angulation after treatment using both hand and rotary instruments. The results indicated that the Reciproc method yielded the smallest mean change in canal angulation (16.9%), followed by ProTaper Universal (21.9%), the Step-Back technique (22.4%), MTwo (26.4%), and finally ProTaper Next, which \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Group** & **N (Canal)** & **Mean** & **Median** & **SD** & **Minimum** & **Maximum** \\ \hline
**STEP-BACK** & 20 & 5.70 & 4.50 & 5.83 & 0 & 24 \\ \hline RECIPROC & 20 & 2.65 & 2.00 & 2.78 & 0 & 11 \\ \hline
**MTWO** & **20** & **4.95** & 2.50 & 5.08 & 0 & 18 \\ \hline PTU & 20 & 4.10 & 2.00 & 6.39 & 0 & 29 \\ \hline
**PTN** & **20** & **5.60** & **5.00** & **5.30** & **0** & **18** \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Angular changes across the groups from the initial apical file to the master apical file (degrees). The conventions are the same as in Table 1. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Group** & **N (Canal)** & **Mean** & **Median** & **SD** & **Minimum** & **Maximum** \\ \hline STEP-BACK & 20 & 22.4 & 18.4 & 13.5 & 0.00 & 46.2 \\ \hline RECIPROC & 20 & 16.9 & 11.8 & 14.7 & 0.00 & 47.2 \\ \hline MTWO & 20 & 26.4 & 19.3 & 13.3 & 4.76 & 58.1 \\ \hline PTU & 20 & 21.9 & 19.9 & 14.9 & 0.00 & 55.8 \\ \hline
**PTN** & **20** & 27.9 & 20.9 & 22.9 & 0.00 & 76.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Angular changes across the groups from the initial apical file to the master apical file (percentages). The conventions are the same as in Table 1.  
showed the largest mean angulation change (27.9%). Based on these findings, the Step-Back technique--still often considered the gold standard--did not produce superior results compared to any other methods, and some methods even showed a trend of better preservation of root canal anatomy. It is important to note that, with the exception of Reciproc, all techniques resulted in similar degrees of change. Even though Reciproc was not significantly more effective than the other techniques in terms of statistical results, it did show a distinct pattern in the observed outcomes, with the smallest mean change in canal angulation. This trend aligns with other studies that highlight its conservative design and ability to minimize intracranial stress, even though the differences were not statistically validated in this study. The lack of statistical significance may stem from factors such as sample size, as larger sample numbers might have been needed to establish significance given the observed variances. Although curved canals are generally more prone to straightening, the lack of statistically significant differences among the groups suggests that all tested techniques effectively preserved root canal anatomy, even in cases with a higher initial curvature. In this context, this study's limited sample size can be considered a limitation, even though it aligns with case numbers seen in similar studies. This outcome is in line with the findings of [PERSON] et al., who observed no significant apical transportation with the Reciproc system when various glide path techniques were applied [35]. Other studies have also highlighted favorable attributes of the Reciproc system, including its ability to achieve full working length without requiring a glide path [36] and its conservative preparation method, which produces minimal intracanal dentinal cracks [37]. The cited study also evaluated the characteristics and usability of basic rotary systems. A comparison between ProTaper Next and MTwo indicated that these systems were among the most flexible, offering a smoother transition between files. The two most widely used systems, each with unique characteristics, were also examined. For instance, ProTaper Next--an evolution of ProTaper Universal--comprises fewer instruments, is more flexible, and features a unique asymmetric motion.