A comprehensive multimethod analysis of mechanical properties of two different heat treatments for endodontic Nickel-titanium instruments

The purpose of the present study was to evaluate the influence of the two different heat treatments of the mechanical properties of two commercial products: X7 Fire-wire and X7 Utopia Nickel-titanium rotary instruments (EdgeEndo, Albuquerque, New Mexico). The present article was written following the guidelines of PRILE (Prefered Reporting Items for Laboratory studies in Endodontology). Since both instruments are available with same design, size and taper the influence of the two different heat treatments on various mechanical properties could be properly evaluated. 50 instruments for each group, as determined by power analysis, were selected and tested using methods and devices validated in previous studies. Data were collected and statistically analyzed using a 1-way ANOVA test followed by the post hoc Tukey test with significance set to a 95% confidence level. Results showed that X7 Utopia were found to be more rigid, with a statistically significant difference when compared to X7 Firewire. Similarly, X7 Utopia were found to be significantly more resistant to torsion, while no statistically significant difference was found between the two tested instruments when subjected to a cyclic fatigue test. Cutting efficiency was significantly higher for X7 Utopia instruments, and also instrumentation time was significantly shorter when compared with X7 Firewire. X7 Firewire instruments showed a higher tendency to flues deformations during usage. We can conclude that thermal treatments of nickel-titanium instruments can significantly impact all their mechanical properties in vitro and overall performance in root canal procedures. Therefore, understanding the differences in thermal treatments is crucial for manufacturers to improve instruments and for dental professionals to tailor these instruments to specific clinical requirements.