Torsional Stress, Cyclic Fatigue, and Thermal Analyses of Heat-Treated and Conventional Nickel-Titanium Rotary Instruments

Abstract

Compare phase-transformation temperatures, torsional-stress properties,and effect of rotational speed per minute (RPM) on cyclic-fatigue life of two proprietarily heat-treated nickel-titanium (NiTi) rotary files (EdgeSequel Sapphire [ESS] and VortexBlue [VB]) to conventional NiTi rotary files (ProFile [P]).Materials and Methods: Torsional moments (TMs) and rotational degrees (RDs) of the files (size=25/0.04, n=20/brand) were measured using a custom-built torsiometer. Effect of RPM on file cyclic-fatigue life was assessed using a custom-built 3-peg jig that constrained files to a simulated curvature (90, r=3.5mm). Files subjected to various RPMs (100, 200, 300, 400, 500, and 600) in air. Measured number of revolutions to fracture (N) per RPM. The phase-transformation temperatures investigated (n=5/brand)by differential scanning calorimeter (DSC). Data analyzed with nonlinear regression and ANOVA/Tukey (=0.05).Results: TMs (g-cm) and RDs () rankings were: VB (758) > P (7213) > ESS (585)and ESS (793122) > VB (51538) and P (51563), respectively. DSC analyses showed ESS (336C) and VB (324C) have austenite finish temperature (Af) below body temperature, P (474C) has Af above body temperature. For ESS and VB, RPM correlated with N, where RPM-N curves were best fitted by power regression, r2=0.987and 0.969 respectively. For P, RPM-N power regression was weakly correlated(r2=0.116).Conclusion: Irrespective of thermal history, files with high TMs conveyed low RDs. Heat-treated files displayed higher cyclic-fatigue resistance than conventional files under similar 100-600 RPM range and have an endurance limit of RPM=100, below which Nwas theoretically infinite. RPM appeared independent of N for conventional files.

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Document Details

Document Type
Technical Report
Publication Date
May 25, 2017
Accession Number
AD1128290

Entities

People

  • D. D. Kersten
  • Joshua D. Gailey
  • P. Mines
  • W. Lien

Organizations

  • Uniformed Services University of the Health Sciences

Tags

Communities of Interest

  • Biomedical
  • Weapons Technologies

DTIC Thesaurus Topics

  • Alloys
  • Austenite
  • Body Temperature
  • Calorimeters
  • Calorimetry
  • Clearances
  • Department Of Defense
  • Elastic Properties
  • Fatigue Life
  • Fatigue Tests (Mechanics)
  • Finishes
  • Heat Energy
  • Materials
  • Mechanical Properties
  • Phase Transformations
  • Resistance
  • Root Canal
  • Tensile Strength
  • Test And Evaluation
  • Thermal Analysis
  • Universities

Readers

  • Allergy and Immunology.
  • Powder metallurgy of Titanium alloys.
  • Tribology (the study of the boundary interaction between sliding surfaces, lubrication, wear and friction).