Mechanical and Metallurgical Properties of Various Nickel-Titanium Rotary Instruments

Abstract

The aim of this study was to investigate the effect of thermomechanical treatment on mechanical and metallurgical properties of nickel-titanium (NiTi) rotary instruments. Eight kinds of NiTi rotary instruments with sizes of ISO #25 were selected: ProFile, K3, and One Shape for the conventional alloy; ProTaper NEXT, Reciproc, and WaveOne for the M-wire alloy; HyFlex CM for the controlled memory- (CM-) wire; and TF for the R-phase alloy. Torsional fracture and cyclic fatigue fracture tests were performed. Products underwent a differential scanning calorimetry (DSC) analysis. The CM-wire and R-phase groups had the lowest elastic modulus, followed by the M-wire group. The maximum torque of the M-wire instrument was comparable to that of a conventional instrument, while those of the CM-wire and R-phase instruments were lower. The angular displacement at failure (ADF) for the CM-wire and R-phase instruments was higher than that of conventional instruments, and ADF of the M-wire instruments was lower. The cyclic fatigue resistance of the thermomechanically treated NiTi instruments was higher. DSC plots revealed that NiTi instruments made with the conventional alloy were primarily composed of austenite at room temperature; stable martensite and R-phase were found in thermomechanically treated instruments.

Bending resistance and cyclic fatigue resistance of WaveOne Gold, Reciproc Blue, and HyFlex EDM instruments

“… 7 , 9 , 25 , 26 , 27 Their cyclic fatigue were both unaffected by rotation rates, despite the difference in their reciprocating angles. 28 Cyclic fatigue can be influenced by cross-sectional area, 2 , 29 instruments with smaller cross-sections have better resistance. 30 In the present study, however, RPB (8% taper) that have larger cross-sectional areas within the 3-mm tip than WOG (7%), had greater resistance to cyclic fatigue.…”

“… 1 Reciprocating rotation increases the cyclic fatigue resistance of NiTi files, compared to continuous rotation. 2 , 3 WaveOne Gold (Dentsply Maillefer, Ballaigues, Switzerland) and Reciproc Blue (VDW GmbH, Munich, Germany) are recently released reciprocating files manufactured with heat treatment. For WaveOne Gold, heat treatment of the NiTi alloy involves a slow heating-cooling process, which generates Ti 3 Ni 4 precipitates dispersed over the surface, 4 and provides greater resistance to cyclic fatigue than M-wire reciprocating files.…”

Cleanliness Efficacy of Neolix and Silk Rotary Systems in Root Canal Retreatment

“…The constant taper throughout the file length with noncutting tip cross-section is teardrop shaped decrease their touching with the canal walls. This could be the major cause for more obturating material remnants located coronally (20) . The tested techniques were not able to completely remove the obturating material.…”

Evaluation of Cyclic Fatigue and Bending Resistance of Coronal Preflaring NiTi File Manufactured with Different Heat Treatments

“…By applying heat treatment to the manufacturing process, NiTi files have become more flexible and more resistant to cyclic fatigue fracture [8,9]. HyFlex CM (Coltène/Whaledent, Altstätten, Switzerland) and HyFlex EDM (Coltène/Whaledent) are made of controlled memory wire (CM wire; DS Dental, Johnson City, TN, USA).…”