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

4. RESULTS AND DISCUSSION
4.1 Flexibility
The stress distribution in the files under 45° bending tests are shown in Fig. 3. A
maximum von Mises stress of 1197 MPa was found for the ProTaper F1 instrument
while the maximum von Mises stress for the Mtwo instrument was 980 MPa.
a)
b)
Figure 3. Stress distribution under 45° bending test: a) ProTaper F1 and b) Mtwo.
The simulated moment required to deflect the F1 files until 45° was greater than the
moment measured to deflect Mtwo (Fig. 4). These results match with the experimental
ones as shown in Fig. 4, where bending moment curves resulted from simulation are
compared with the experimental average curves with standard error bars.
Moment (N.cm)
0,7
0,6
0,5
0,4
0,3
0,2
0,1
Experimental
Numerical
0,0
0 5 10 15 20 25 30 35 40 45
Bending ( )
a)
0
0 5 10 15 20 25 30 35 40 45
Bending ( )
Figure 4. Numerical bending moment compared with the experimental one: a) ProTaper F1 and b) Mtwo.
The flexibility of endodontic instruments depends on their metallurgic properties and
their geometric shape and size. Once the metallurgic properties used for the simulation
are the same for both instruments, the differences in flexibility observed here between
Moment (N.cm)
0,5
0,4
0,3
0,2
0,1
Experimental
Numerical
b)