Comparative Assessment of The Fracture Resistance of Teeth Instrumented by Two Different Nickel Titanium Rotary Systems

Aim: This study aimed to compare the fracture resistance exhibited by roots on instrumentation using two endodontic rotary systems: SANI S3 and EdgeEndo X7 rotary file systems. Materials and Methods: Sixty recently extracted human mandibular premolars comprising single root canals were selected in this study. All specimens were decoronated and mounted perpendicularly in self-cure acrylic resin blocks exposing 6 mm of the roots out of the acrylic resin blocks. The specimens were divided into two experimental groups, according to NiTi rotary systems used and one control group (n = 20). After instrumentation, the specimens of both experimental groups were then filled using master Gutta-percha cones size 35 (0.04 taper) and obturation was done using continuous wave compaction technique. The specimens were kept at 37 °C and 100% humidity for 2 weeks to allow complete setting of the sealer. Root fracture resistance was assessed using a universal testing machine (Instron) and the amount of load necessary for root fracture was recorded in Newtons (N). Statistics: Data were collected, tabulated and statistically analyzed using one-way ANOVA test and Tukey’s posthoc test. Results: Group C (control) exhibited the highest mean fracture force (357.13 ± 20.61) while group A (SANI S3) showed the lowest mean fracture force (192.60 ± 22.73). One-way ANOVA test showed statistically significant differences between tested groups. Regarding inter-group comparisons using Tukey’s test, there was a significant statistical difference between groups (A and B) and between groups (A and C). Furthermore, there was a statistically significant difference between groups (B and C). (P?0.05) Conclusion: 1-Root canal instrumentation with NiTi rotary files possessed a negative impact on roots and higher risks of root fractures compared to intact unprepared roots. 2-Design of NiTi files with improved cutting efficiency could diminish the risk of crack formation in root canal dentinal walls.