Journal
JOURNAL OF ENDODONTICS
Volume 43, Issue 8, Pages 1337-1342Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.joen.2017.03.024
Keywords
Cyclic fatigue; fracture; high-speed camera; nickel-titanium rotary instrument; reciprocating; scanning electron microscope; torsional fatigue
Categories
Funding
- Japan Society for the Promotion of Science [15K20400]
- Grants-in-Aid for Scientific Research [15K20400] Funding Source: KAKEN
Ask authors/readers for more resources
Introduction: This study examined the dynamic fracture behavior of nickel-titanium rotary instruments in' torsional or cyclic loading at continuous or reciprocating rotation by means of high-speed digital video imaging. Methods: The.ProFile instruments (size 30, 0.06 taper; Dentsply Maillefer, Ballaigues, Switzerland) were categorized into 4 groups (n = 7 in each group) as follows: torsional/continuous (TC), torsional/reciprocating (TR), cyclic/continuous (CC), and cyclic/reciprocating (CR). Torsional loading was performed by rotating the instruments by holding the tip with a vise. For cyclic loading, a custom-made device with a 38 curvature was used. Dynamic fracture behavior was observed with a highspeed camera. The time to fracture was recorded, and the fractured surface was examined with scanning electron microscopy. Results: The TC group initially exhibited necking of the file followed by the development of an initial crack line. The TR group demonstrated opening and closing of a crack according to its rotation in the cutting and noncutting directions, respectively. The CC group separated without any detectable signs of deformation. In the CR group, initial crack formation was recognized in 5 of 7 samples. The reciprocating rotation exhibited a longer time to fracture in both torsional and cyclic fatigue testing (P < .05). The scanning electron microscopic images showed a severely deformed surface in the TR group. Conclusions: The dynamic fracture behavior of NiTi rotary instruments, as visualized with high-speed digital video imaging, varied between the different modes of rotation and different fatigue testing. Reciprocating rotation induced a slower crack propagation and conferred higher fatigue resistance than continuous rotation in both torsional and cyclic loads.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available