Metallurgical characterization of a new nickel-titanium wire for rotary endodontic instruments.
BACKGROUND
A novel thermomechanical processing procedure has been developed that yields a superelastic (SE) nickel-titanium (NiTi) wire (M-Wire) that laboratory testing shows has improved mechanical properties compared with conventional SE austenitic NiTi wires used for manufacture of rotary instruments. The objective of this study was to determine the origin of the improved mechanical properties.


METHODS
Specimens from 2 batches of M-Wire prepared under different processing conditions and from 1 batch of standard-processed SE wire for rotary instruments were examined by scanning transmission electron microscopy, temperature-modulated differential scanning calorimetry, micro-x-ray diffraction, and scanning electron microscopy with x-ray energy-dispersive spectrometric analyses.


RESULTS
The processing for M-Wire yields a microstructure containing martensite, that the proportions of NiTi phases depend on processing conditions, and that the microstructure exhibits pronounced evidence of alloy strengthening.


CONCLUSIONS
The presence of Ti(2)Ni precipitates in both microstructures indicates that M-Wire and the conventional SE wire for rotary instruments are titanium-rich.
Department of Materials Science, College of Dental Medicine, Medical University of South Carolina, Charleston, South Carolina, USA.
Satish B
SB
Alapati
William A
WA
Brantley
Masahiro
M
Iijima
William A T
WA
Clark
Libor
L
Kovarik
Caesar
C
Buie
Jie
J
Liu
William
W
Ben Johnson
D002152:Calorimetry, Differential Scanning; D003080:Cold Temperature; D003722:Dental Alloys / Q000032:analysis / Q000737:chemistry*; D004548:Elasticity; D004577:Electron Probe Microanalysis; D004867:Equipment Design; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D055595:Mechanical Phenomena; D008669:Metallurgy; D017348:Microscopy, Electron, Scanning Transmission; D009532:Nickel / Q000032:analysis / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D014025:Titanium / Q000032:analysis / Q000737:chemistry*; D014961:X-Ray Diffraction
D003722:Dental Alloys; C040654:titanium nickelide; C093824:Martensite; D009532:Nickel; D014025:Titanium