Torsional profiles of new and used 20/.06 GT series X and GT rotary endodontic instruments.

Introduction: M-Wire (Sportswire LLC, Langley, OK) is reportedly created by altering alloy temperatures during the manufacturing process of GT series X instruments (Dentsply Tulsa Dental Specialties, Tulsa, OK). Currently, there are few published studies looking at torsional profiles of these instruments. The purpose of this study was to investigate the torsional profiles of new and used 20/0.06 GT series X (GTX) and GT (GT) instruments (Dentsply Tulsa Dental Specialties).
Methods: Thirty instruments were allocated to one of eight groups and were used 2, 6, or 10 times in simulated canals or remained as unused controls. Testing of torque (TF) and angle at fracture (AF) were conducted in accordance with American National Standards Institute/American Dental Association (ANSI/ADA) specification No. 28. Data analyses were performed by using one- and two- way analysis of variance with honesty significance difference post hoc comparison with alpha = 0.05.
Results: Overall, there were significant differences in TF and AF among the experimental groups (p < 0.001). GTX instruments showed a significant initial increase in TF with two and six uses (p < 0.001) in contrast to the GT, which showed a linear reduction in TF with increased use (p < 0.004). Both GTX and GT instruments showed no statistical difference in AF of new instruments but did show a significant decrease in AF in all groups except the GT two-use group (p < 0.02).
Conclusion: The GTX instruments had a higher resistance to torsional failure after use as compared with the GT.