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Cyclic Fatigue Resistance of 'Replica-Like" and Original Reciprocating Instruments in Single and Double Curvatures
Celia Tarragó1, Oliver Valencia De Pablo1, Gaizka Loroño1
1Postgraduate Programme in Endodontics, European University of Madrid, Madrid, Spain.
European Endodontic Journal
|June 4, 2025
Summary
Heat-treated reciprocating instruments demonstrated superior cyclic fatigue resistance compared to conventional ones, with tip sizes smaller than manufacturer claims. Double curvatures significantly reduced instrument lifespan.
Area of Science:
- Endodontics
- Materials Science
Background:
- Reciprocating instruments are widely used in endodontic treatments.
- Heat treatment enhances the mechanical properties of nickel-titanium (NiTi) rotary instruments.
- Understanding cyclic fatigue resistance is crucial for instrument longevity and clinical success.
Purpose of the Study:
- To compare the cyclic fatigue resistance of conventional and heat-treated reciprocating instruments.
- To evaluate the influence of single and double curvatures on instrument fatigue life.
- To assess the accuracy of manufacturer-reported tip sizes for these instruments.
Main Methods:
- Eighteen instruments per group were subjected to cyclic fatigue testing.
- Cyclic fatigue resistance was evaluated under single (60°, 5 mm radius) and double curvatures (60°, 5 mm radius each) at 37°C.
- Time to fracture was recorded and statistically analyzed.
Main Results:
- All tested instruments exhibited tip sizes smaller than manufacturer specifications.
- Heat-treated instruments (Reciproc Blue, Reverso Blue) showed significantly higher cyclic fatigue resistance than conventional counterparts (Reciproc R25, Reverso Silver).
- Double curvatures significantly reduced the time to fracture for most instrument groups compared to single curvatures.
Conclusions:
- Manufacturer-reported tip sizes for reciprocating instruments may not be accurate.
- Heat-treated reciprocating instruments offer enhanced cyclic fatigue resistance.
- Complex root canal geometries, particularly double curvatures, accelerate instrument fatigue and fracture risk.
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