Movement kinematics and cyclic fatigue of NiTi rotary instruments

By Ferreira F, Adeodato C, Barbosa I1, Aboud L, Scelza P, Zaccaro Scelza M.

Date: 02/2019
Journal: IEJ

Summary: 

Purpose: To provide a detailed analysis of the literature concerning the correlation between different movement kinematics and the cyclic fatigue resistance of NiTi rotary endodontic instruments.

Materials/Methods:

N=20 articles were included (qualitative synthesis comparing both reciprocating and continuous movements to cyclic fatigue of the instruments) after comprehensive and systematic searching of the Medline (PubMed), EMBASE, Web of Science, Scopus and Google Scholar databases for works published since January 2005, using the following search terms: endodontics; nickel–titanium rotary files; continuous rotation; reciprocating motion; cyclic fatigue.

Most highlighted Results: 

-The use of reciprocating motion can improve the mechanical properties of instruments and increase fatigue resistance, compared to continuous rotation (Kim et al. 2012)

-An important point to consider is that the mean time to fracture is not directly proportional to the increase in the number of reciprocations required to complete a full 360 rotation (because the resulting speeds are not directly proportional) (Gambarini et al. 2012).

-The findings of several studies suggest that reciprocating motion improves the cyclic fatigue resistance of instruments, compared to continuous rotation, independent of other variables such as the speed of rotation, the angle of curvature of the simulated canal and NiTi instrument design.