Investigating Torsional Force and Angle of Rotation to Fracture of XP-3D Shaper NiTi Rotary Files

Objective: Heat treatment of nickel-titanium rotary file instruments has been demonstrated to be more efficient for conventional root canal therapy. This in vitro study compared the torsional force to fracture (TFF) and angle of rotation to fracture (ARF) of XP-3D Shaper conforming Nickel Titanium (NiTi) rotary files in as-received condition and after 1 and 3 simulated clinical uses. Methods: Simulated root canals (30-degree curvature) in clear resin blocks were used. 25 mm length XP-3D Shaper files 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). SEM analysis of the separated portion was also performed. Results: The XP-3D Shaper demonstrated no significant difference (p>0.05) in TFF between as-received and 1 use, as-received and 3 uses, and 1 use and 3 uses. There was a significant (p<0.002) decrease in ARF between the XP-3D Shaper as received and 1 use, as-received and 3 uses, and between 1 use and 3 uses. Conclusions: There is no significant difference (p>0.05) in TFF between the XP-3D Shaper files as-received, after 1 use, and after 3 uses. There is a significant difference (p<0.002) in ARF between the XP-3D Shaper files as-received, after 1 use, and after 3 uses. The possible explanation for these results could be due to the non-linear file design in combination with the heat treatment of the nickel-titanium.