Impact of a modified motion on the fatigue life of NiTi reciprocating instruments: a Weibull analysis

Objectives To evaluate the impact of a modified motion on the fatigue life of four brands of nickel–titanium (NiTi) reciprocating instruments. Materials and methods Cyclic fatigue (CF) resistance of 160 instruments was evaluated in an artificial stainless-steel canal (90° angle, 5-mm radius of curvature). WaveOne and WaveOne Gold (Denstply Maillefer, Baillagues, Switzerland) and Reciproc and Reciproc Blue (VDW, Munich, Germany) were tested with two different motions: (1) X-Smart Plus (Denstply Maillefer) endodontic motor and (2) a 4:1 contra-angle with an experimental motion (EVO) with different rotation angles and based on a sinusoidal acceleration. Motions with X-Smart Plus and EVO were recorded and analyzed at a reduced speed with VLC Media Player software for a more accurate analysis. Mean half-life, beta, and eta Weibull parameters were determined and compared. Results Reciproc Blue resulted the most resistant instruments either with EVO or X-Smart. WaveOne Gold lasted significantly longer than WaveOne with EVO (probability of 91%) while no significant differences were found with X-Smart. Considering NCF, Reciproc, WaveOne Gold, and Reciproc Blue lasted significantly longer with EVO (prob- abilities of 66%, 80%, and 89% respectively). WaveOne Gold showed the highest beta parameter. Conclusions The experimental motion was found to have a positive impact on fatigue lifetime of reciprocating instruments. Clinical relevance Current findings provide insight for future improvements in the clinical use of reciprocating files. Experimental motions may be considered when searching for additional strategies in order to increase the safer use of NiTi files during endodontic procedures.