Abstract
Introduction
The aim of this study was to investigate the influence of mass and the polar moment
of inertia on the torsional behavior of nickel-titanium rotary instruments to understand
which parameter of cross-sectional design had a key role in terms of torsional resistance.
Methods
Four different instrument models were designed and meshed using computer-aided engineering
software (SolidWorks; Dassault Systems, Waltham, MA). Instrument models shared the
same characteristics, except for cross-sectional design; triangle, rectangle, square,
and hollow square geometry was selected. Finite element analysis was performed simulating
a static torsional test using the FEEPlus internal solver (Solid Works). Von Mises
stress and torsional load at fracture were calculated by the software. Linear regression
analysis was performed to investigate the relationship of the polar moment of inertia,
cross-sectional area, inner core radius, and mass per volume on the torsional resistance
of nickel-titanium rotary instruments.
Results
The polar moment of inertia positively affected the maximum torsional load with the
highest level of correlation (R2 = 0.917). It could be stated that the higher the polar moment of inertia is, the
more maximum torsional load at fracture is present. Mass and cross-sectional area
had a lower level of correlation compared with the polar moment of inertia (R2 = 0.5533). According to this, 2 instruments with the same mass/mm and/or cross-sectional
area could have different torsional resistance.
Conclusions
The polar moment of inertia can be considered as the most important cross-sectional
factor in determining the torsional resistance of rotary instruments over metal mass
and cross-sectional area.
Key Words
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Article info
Publication history
Published online: April 26, 2021
Accepted:
April 14,
2021
Received in revised form:
March 16,
2021
Received:
December 8,
2020
Identification
Copyright
© 2021 American Association of Endodontists.
