Investigation of Torsional Force and Angle of Rotation to Fracture of Trushape® NiTi Rotary Instruments.

Objective: This in vitro study compared the torsional force to fracture (TFF) and angle of rotation to fracture (ARF) of Trushape® 3D conforming Nickel Titanium (NiTi) rotary files in as received condition, after 1, and 3 simulated clinical uses. Methods: Ninety simulated root canals (30-degree curvature) in clear resin blocks (A0177, DENTSPLY Maillefer) were used. 25 mm length files with 6% taper in sizes 20, 25 and 30 were tested (n=10 per test group). TFF and ARF were recorded with torsiometer (Sabri Dental Enterprises) as per ISO 3630-1. TFF was obtained by measuring peak torque in gram-centimeters (g-cm) and ARF in degrees of rotation until instrument separation. The data was analyzed using ANOVA and Tukey’s Post-Hoc tests (p<0.05) Results: The TFF significantly (p<0.05) decreased between as received and 3 use files within each file size. In addition, there was also a significant (p<0.05) decrease in TFF between the 1 use and 3 use of 25/06 file size. The ARF significantly (p<0.05) decreased between as received and 3 use within each file size. In addition, there was a significant (p<0.05) difference between as received and 1 use files of 20/06 and 25/06 file sizes; between 1 use and 3 use files of 25/06 and 30/06 file sizes. Conclusions: Within each specific file size, there is a trend of decreasing TFF and ARF with increased usage. Between the different file size groups, there is a significant (p<0.05) increase in TFF and AR to file separation with increase in file size.