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Influence of cyclic loading in NiTi austenitic and R-phase endodontic files from a finite element perspective
Suzanny C S Martins1, Jessica D Silva1, Paula R Garcia2
1Department of Metallurgical and Materials Engineering, School of Engineering, Universidade Federal de Minas Gerais (UFMG), Av. Antônio Carlos, 6627-Campus Pampulha, Belo Horizonte, MG, 31270-901, Brazil.
Objectives:
This study aims to evaluate the effects of cyclic loading on the bending moments and the developed stress state of austenitic and R-phase endodontic files through finite element analysis.
Materials And Methods:
The mechanical properties of two groups of NiTi wires, austenite and R-phase, were measured in samples at two different conditions: uncycled and cycled. The cycled condition was achieved by subjecting samples of the two groups to 80% of the corresponding fatigue life under rotating bending efforts. The measured mechanical properties were then used in the finite element analysis, where the boundary and loading conditions were set to replicate a standard bending test.
Results:
The results showed that mechanical cycling leads to decreasing stress levels and bending moments in the simulated files, especially in the austenitic ones. In comparison with austenite, R-phase presented a more stable mechanical behavior during cycling.
Conclusions:
The results show that the moment and stress calculated for an instrument under bending can be considerably decreased after some cyclic work.
Clinical Relevance:
The fatigue related to the clinical use of an endodontic file decreases the moment (as well as the forces) imposed by the instrument during the shaping of a curved root canal. This decrease is directly related to the type of atomic array present in the alloy.
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