ABSTRACT
OBJECTIVE:
The purpose of this study was to assess the
role of cross section on cyclic
fatigue resistance of One Shape, Revo-S SU, and Mtwo rotary files in continuous
rotation and reciprocating
motion in dynamic testing model. MATERIALS AND
METHODS:
A total of 90 new rotary One Shape, Revo-S SU, and Mtwo files (ISO size 25, taper 0.06, length 25 mm) were subjected to continuous
rotation or reciprocating
motion. A cyclic
fatigue testing
device was fabricated with 60° angle of curvature and 5 mm
radius. The dynamic testing of these files was performed using an electric motor which permitted the
reproduction of pecking
motion. All instruments were rotated or reciprocated until fracture occurred. The
time taken for each instrument to fracture was recorded. All the fractured files were analyzed under a scanning
electron microscope (SEM) to detect the mode of fracture.
Statistical analysis was performed using one-way
ANOVA, followed by Tukey's honestly significant difference post hoc test.
RESULTS:
The
time taken for instruments in reciprocating
motion to fail under cyclic loading was significantly longer when compared with groups in continuous rotary
motion. There was a statistically significant difference between Mtwo rotary and the other two groups in both continuous and reciprocating
motion. One Shape rotary files recorded significantly longer duration to fracture resistance when compared with Revo-S SU files in both continuous and reciprocating
motion. SEM observations showed that the instruments of all groups had undergone a ductile mode of fracture.
CONCLUSION:
Reciprocating
motion improved the cyclic
fatigue resistance of all tested groups.
