Cyclic Fatigue
The progressive structural failure of a rotary endodontic file caused by repeated tension-compression stress cycles as it rotates within a curved canal.
Full Definition
Cyclic fatigue occurs when a rotating endodontic instrument undergoes alternating tensile and compressive stresses at the point of maximum curvature, leading to crack initiation and eventual separation without prior visible deformation. It is distinct from torsional fracture, which results from the file tip binding while the shank continues to rotate. Editors must not conflate these two failure modes. The term is always hyphenated. In vitro testing articles often express cyclic fatigue as 'number of cycles to fracture (NCF),' which editors should ensure is defined on first use.
Usage
Usage note: Always hyphenate: 'cyclic-fatigue resistance'. Distinguish from torsional fracture, which has a different aetiology, when editing materials-science sections.
In Context
- "Cyclic fatigue resistance was measured in a simulated curved canal at 60° of curvature." — Laboratory study on file performance
- "The authors attributed instrument separation to cyclic fatigue rather than torsional overload." — Case series discussion section