Scanning Electron Microscopic Evaluation
The fractured surfaces of 5 instruments of each file, randomly selected
after cyclic and torsional fatigue tests, were examined by scanning
electron microscopy JSM-6060 (Jeol Brasil Ltda, Mirandópolis, São Paulo)
to look for the topographic features of the fractured instruments.
Before scanning electron microscopic (SEM) evaluation, instruments were
ultrasonically cleaned to remove debris. The photomicrographs were taken
at 200X magnification. Furthermore, additional photomicrographs were
taken at 1000X magnification in the center of the fractured surface of
the instruments submitted to torsional testing.
RESULTS
The mean and standard deviation values of the cyclic (seconds) and
torsional (maximum torque), and angular deflection (rotation angle)
fatigue tests are shown in Table 1.
Regarding the cyclic fatigue in continuous motion, Flat File 25.04
instruments showed the lowest cyclic fatigue resistance than the Logic
25.03 and 25.05 instruments (P < .05). In addition, Logic
25.03 presented the highest cyclic fatigue resistance (P <
.05). In reciprocating motion, all instruments had higher cyclic fatigue
resistance than when activated in continuous motion (P< .05).
The Flat File 25.04 showed the lowest values of cyclic fatigue
resistance when compared to Logic 25.03 and Logic 25.05 (P<
.05). Logic 25.03 presented higher cyclic fatigue resistance values than
Logic 25.05 (P< .05)
The torsional test showed that the Flat 25.04 instruments presented
similar torque to the Logic 25.05 instrument (P > .05). The
Logic 25.03 instrument presented the lowest torque values (P
< .05). Regarding the angular deflection, all the instruments
had significantly different values, according to the following
decreasing order: Logic 25.03, 25.05, and Flat File 25.04
(P<.05)