ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

F1 and Mtwo were directly related to the variations these instruments exhibited in their
geometry. It is know that the flexibility is inversely proportional to the moment of
inertia of the material, which can explain higher flexibility found for the Mtwo
instrument. The mechanical behavior simulated for the instruments is in accordance
with the bending experimental results, indicating the reliability of the numerical model.
4.2 Torsional strength
The stress distribution in the files under simulated 80° torsion tests are shown in Fig. 5,
with respective cross sections. The maximum calculated von Mises stress for F1 was
1609 MPa and for Mtwo was 1510 MPa.
Figure 5. Stress distribution under 80° torsion test: a) ProTaper F1 with maximum stress 3,52 mm from
the tip and b) Mtwo with maximum stress 3,40 mm from the tip.
The torque necessary to rotate the F1 file until 80° was greater than the torque measured
for the Mtwo instrument. The calculated torque curves are compared to the
experimental average ones with their standard error bars in Fig. 6.
Torque (N.cm)
0,7
0,6
0,5
0,4
0,3
0,2
0,1
Experimental
Numerical
0
0 10 20 30 40
Rotation ( )
50 60 70 80
Figure 6. Numerical torque compared with the experimental one: a) ProTaper F1 and b) Mtwo.
Despite the proximity in terms of stress distribution pattern found for both instruments,
the results still show a considerable difference between the values of torque necessary to
rotate the instruments. The torque strength is proportional to the polar moment of
inertia, explaining the higher strength found for the F1 instrument in comparison to the
Mtwo. The difference of behavior observed between calculated and experimental curves
Torque (N.cm)
0,5
0,4
0,3
0,2
0,1
Experimental
Numerical
a)
b)
0
0 10 20 30 40
Rotation ( )
50 60 70 80
a) b)