Reciprocation Cyclic Fatigue — ORE Part 1 MCQ

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ModerateDental MaterialsReciprocation Cyclic FatigueORE Part 1

Compared with continuous rotation, what is the principal mechanical advantage of using reciprocating motion for a nickel-titanium endodontic file?

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Correct answer: E — Greater resistance to cyclic fatigue

Explanation lettering: D = shown as A · E = shown as B · B = shown as D · A = shown as E

A is correct. Reciprocating motion alternates directions rather than maintaining continuous unidirectional rotation. In curved canals, this reduces the accumulated tensile–compressive loading associated with cyclic fatigue, so NiTi files generally withstand more cycles before fracture than comparable files in continuous rotation. Systematic reviews and meta-analysis support greater cyclic-fatigue resistance with reciprocation, although alloy, cross-section, heat treatment and canal curvature also influence performance. B is not the principal established advantage and cutting efficiency depends on the specific instrument design and motion programme. C is incorrect because irrigant penetration depends mainly on irrigation technique and canal preparation. D is unrelated to file kinematics. E is not an inherent property of reciprocation; costs depend on the file system and practice protocol.

Reference: De Pedro-Muñoz A, et al. Cyclic Fatigue Resistance of Rotary versus Reciprocating Endodontic Files: A Systematic Review and Meta-Analysis. Journal of Clinical Medicine, 2024. https://pubmed.ncbi.nlm.nih.gov/27185740/