Assessment of the role of cross section on fatigue resistance of rotary files when used in reciprocation

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.

Influence of the type of reciprocating motion on the cyclic fatigue resistance of reciprocating files in a dynamic model

“…Regardless of the alloy of the reciprocating system, the cross-section that showed the best response to cyclic fatigue was the double-S cross-section of Reciproc and Reciproc Blue, which was the same as Procodile. Similarly, Sekar et al [ 19 ] reported in their study that the cross-section that had the most influence on cyclic fatigue resistance was the double-S cross-section of Mtwo endodontic rotary files. Alsilani et al [ 20 ] stated that the double-S cross-section of the Reciproc system presented a statistically significantly ( p < 0.001) mean time to failure (301.13 ± 54.463/836.53 ± 67.960 s) compared to One Shape (187.73 ± 33.457/275.27 ± 58.410 s) and Revo-S SU (116.67 ± 37.663/197.60 ± 41.092 s) in both continuous rotation and reciprocating movement.…”

Static Flexural Cyclic Fatigue of Two Rotary File Systems (An in Vitro Study)

“…In agreement with our results, Ataya et al, (31) found T-Wire heat treatment drastically enhanced the cyclic fatigue resistance of heat-treated OneFlare files when compared with conventional OneFlare files. Whereas, Sekar et al, (26) found that M-two files had higher cyclic fatigue resistance than OS. Moreover, Gündoğar & Özyürek (32) found that The HyFlex EDM files had the greatest number of cycles to fracture while the OS files had the least among all tested files.…”

“…The artificial canal had 60° angle, 5 mm radius of curvature and maximum convexity is 5 mm from the tip of the canal. These specific parameters were chosen as most of the cyclic fatigue studies used them (26,27).…”

“…This making us excluded the file's cross section as causative factor of the resulted difference in the cyclic fatigue resistance between the two files systems. The crosssectional area of the file has a significant effect in the cyclic fatigue resistance as Sekar et al, (26) found that the smaller cross-sectional area of the file, the greater cyclic resistance would be. In the results of our study, we found one specimen from OneShape (#2) and three specimens from TwoShape (#22, #23 and #28) at the specimen distribution were outliers (had extreme reading), we attributed that to the manufactural defects.…”

Comparison of transverse strength of three different types of heat cured resin acrylics

“…Resistance to cyclic fatigue depends on various factors such as diameter, metal mass, fl exibility, cross-sectional shape, regressive surface area, and presence of transitional zones in fi les. One Shape rotary fi les could have experienced more stress cycles of tension and compression per minute when compared to two for the same time period (Sekar et al, 2016). It is reported number of…”