A Comparison of Torsional Stress Properties of Three Different Nickel-Titanium Files with Similar Cross-Sectional Design

A COMPARISON OF TORSIONAL STRESS PROPERTIES OF THREE DIFFERENT NICKEL-TITANIUM FILES WITH SIMILAR CROSS-SECTIONAL DESIGN Reid C. Wycoff D.D.S. Marquette University, 2012 The purpose of this study was to compare the in vitro torsional stress characteristics of Twisted Files (SybronEndo, Orange, CA) with two milled files of similar cross section, EndoSequence (Brasseler USA, Savannah, GA) and ProFile Vortex (DENTSPLY Tulsa Dental, Tulsa, OK). Files of size 25/.06 and 30/.06 from the three file types were compared (n=20/group). Torsional stress resistance was evaluated by measuring the torque in gram-centimeters (g-cm) and angle of rotation (degrees) required for instrument separation with use of a torsiometer instrument. The fractured files were examined using SEM to look at deformation and fracture surface characteristics. The data was analyzed with ANOVA to determine statistical differences. The three file types showed a statistically significant difference in both maximum torsional stress and angle of rotation prior to failure. Twisted Files displayed the least amount of torsional stress resistance and the highest angle of rotation. The 30/.06 size files of all three types withstood more torsional stress than the size 25/06 files of the same type. Within each file design, there was not a statistically significant difference in angular rotation between the 25/.06 and 30/.06 groups. The SEM analysis of all three file types revealed dimpling near the center of rotation on the fractured surface indicative of torsional stress. The novel techniques used in manufacturing Twisted Files do not make them more resistant to torsional stress as compared with milled nickel-titanium endodontic files of similar cross-sectional design.