A Critical Analysis on the Cyclic Fatigue Testing of Rotary Endodontic Instrument

摘要

Cyclic fatigue of rotary endodontic instruments has been tested using different techniques while the results were normally compared in terms of a canal curvature radius R and an angular extent of instrument insertion θ. In this work, the effects of canal geometry and analysis method have been investigated by finite element (FE) analysis. A highly simplified FE model has been proposed and verified experimentally. Results from a detailed finite element (FE) model and a simple geometric model are discussed in the light of the simplified model results. It was found that the commonly used (R, θ) alone cannot quantify the severity of bending. The diameters and taper development of the canal and the instrument also played important roles. The simple geometric model can give unacceptable errors and cannot only be employed forensically. The detailed finite element model is much more resource consuming than the current simplified model and the extra effort is not worthwhile if only the bending strain is needed for correlation and prediction of instrument fatigue life.