Objective: This study aimed to compare the fracture resistance of human mandibular premolar roots after instrumentation with different nickel–titanium (NiTi) rotary Systems. Methods: Forty extracted human mandibular premolars were decoronated and randomly assigned to four groups (n=10). Group 1 served as an uninstrumented control, while Groups 2–4 were prepared using different NiTi rotary Systems according to the manufacturers’ protocols: One Curve (OC) Single-file System (Group 2), XP-Endo Shaper (XPS) Single-file System (Group 3), and ProTaper NEXT (PTN) multi-file System (Group 4). All instrumented canals were obturated with gutta-percha and AH Plus sealer using the lateral compaction technique. Vertical fracture resistance was then tested with a universal testing machine. Data were analyzed using one-way ANOVA followed by Tukey’s post hoc test (α=0.05). Results: ANOVA revealed a significant difference in fracture resistance among the groups (P=0.005). The control group (402 ± 115.93 N) showed significantly higher mean fracture resistance compared to all instrumented groups (P < 0.05). Among the instrumented groups, XPS (304 ± 37.47 N) had the highest mean fracture resistance, followed by OC (291 ± 78.37 N) and PTN (288 ± 50.50 N), but these differences were not statistically significant (P > 0.05). Conclusions: Root canal instrumentation with both Single-file and multi-file NiTi rotary Systems significantly reduced fracture resistance compared to uninstrumented roots. There was no significant difference in fracture resistance between the Single-file and multi-file Systems, indicating that the Single-file approach does not provide an advantage in preserving root strength.

Introduction: This study aimed to evaluate the cyclic fatigue resistance of two Single file engine-driven instruments, Reciproc and NeoNiTi, in simulated root canals. Methods and Materials: Two groups of 15 NiTi endodontic instruments with an identical tip size of 0. 25 mm were tested: Reciproc R25 (group A) and NeoNiTi A1 (group B). Cyclic fatigue testing was performed in a stainless steel artificial canal. The simulated canals had a 60° angle and 5-mm radius curvature. The Reciproc instruments were operated using the preset program on torque control electric motor specific for the Reciproc instruments, while the NeoNiTi instruments were operated using the manufacturer recommendation. All instruments were rotated until fracture occurred, and the number of cycles to fracture (NCF) and the length of the fractured tip were recorded and registered. Means and standard deviations of NCF and fragment length were calculated for each System and data were subjected to Student’ s t test (P<0. 05). Results: A statistically significant difference (P<0. 05) was noted between Reciproc and NeoNiTi instruments. NeoNiTi A1 instruments were associated with a significantly higher mean NCF as compared to Reciproc R25 instruments (833± 176 vs. 318± 87 NCF). There was no significant difference (P>0. 05) in the mean length of the fractured fragments between the instruments. Conclusion: NeoNiTi instruments were associated with a significantly higher cyclic fatigue resistance than Reciproc instruments.

Introduction: The present study aimed to compare the capability of two Single-file shaping Systems in disinfecting and cleaning long oval root canals. Materials and Methods: Fifty Single-rooted teeth were prepared, contaminated with Enterococcus faecalis and divided into two groups. Two samplings were obtained,S1 before chemo-mechanical preparation and S2 after the preparation. Depending on the group, chemo-mechanical preparation was performed with XP-endo Shaper (XPS) and Wave One Gold (WOG). Five teeth from each group were observed under scanning electron microscopy (1000×) to evaluate the cleanliness of root canals at 3, 6 and 9 mm from the apex. All probability (P-values) were two-tailed, statistical significance was set at 0. 05 and analyses were conducted using SPSS statistical software. Results: A significant reduction in the colony forming units was observed from S1 to S2 in both tested groups. In S2, XPS group obtained significantly lower colony forming units (P<0. 001). In the cleanliness study, XPS group resulted in significantly cleaner canals compared to WOG. Conclusions: Based on this in vitro study XPS System was more effective in disinfecting and cleaning long oval canals.