Impact of metallurgical features and cross-sectional design on the cyclic and torsional properties of NiTi rotary instruments

Author(s)

Cordova, Abel Victor Isidro Teves ; Alcalde, Murilo Priori ; Vivan, Rodrigo Ricci ; Baldarrago, Andres Castrejon ; Munoz, Diego Quispe ; Guzman, Hubert Ponce ; Calefi, Pedro Souza ; Correa, Diego Rafael Nespeque ; Grandini, Carlos Roberto ; Duarte, Marco Antonio Hungaro

• Document type: Journal article
• Source: JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T; v. 36, p. 8-pg., 2025-05-01.

Abstract

This study evaluated six NiTi rotary instruments' mechanical and metallurgical properties with varying thermal treatments and cross-sections. A total of 240 instruments (sizes 25.06 and 35.04) were tested: VDW Rotate (VDW), Plex V (PV), Pro-Flexi Files (PFF), MG3 Gold (MG3), RCS Rainbow One (RRO), and AF F One (AFR). Cyclic fatigue resistance was assessed in an artificial canal (60 degrees curvature, 5 mm radius) (n = 20), and torsional strength was measured by maximum torque and angular deflection at the instrument tip (n = 20). Metallurgical properties were analyzed using Differential Scanning Calorimetry (DSC) and X-ray Diffraction (X-RD). ANOVA and Tukey tests were applied (alpha = 5 %). RRO 25.06 showed the highest NCF (Number of Cycles to Fracture) (p < 0.05), while RRO 25.06 and PFF 25.06 had the lowest torsional strength (p < 0.05). For size 35.04, RRO and PFF exhibited the highest NCF (p < 0.05), whereas MG3 had the lowest torsional strength (p < 0.05). DSC analysis revealed that VDW instruments had the lowest austenite start and finish temperatures. X-RD showed the highest austenite content in VDW 25.06 and AFR 35.04. Mechanical resistance varied significantly among instruments, with DSC and X-RD confirming distinct metallurgical features strongly influencing performance. Phase quantification and its correlation with laboratory data improve understanding new thermally treated files. (AU)

• FAPESP's process: 21/13921-3 - Development of a low cost high entropy alloy for potential use as bone fixation devices
• Grantee: Jhuliene Elen Muro Torrento
• Support Opportunities: Scholarships in Brazil - Doctorate