Fatigue resistance of traditional solid rotational endodontic instruments and a prototype non-solid instrument

E.A. Rzhanov* & T.S. Belyaeva
Department of Operative Dentistry and Endodontics, Moscow State University of Medicine and Dentistry, Moscow, Russia

To compare the cyclic fatigue resistance of traditional solid rotational nickel-titanium endodontic instruments and a prototype steel super-flexible non-solid endodontic instrument.

Four types of solidrotational nickel-titanium endodontic instruments: LightSpeed size 35 (LightSpeed Technology, USA), RaCe size 20 0.02 (FKG Dentaire, Switzerland), FlexMaster size 20, 0.02 taper (VDW, Germany), PathFile 019 (DentsplyMaillefer, Switzerland) and a prototype non-solid rotational steel instrument were investigated. Fatigue testing was carried out in specially prepared, transparent glass tubes. Tubes were bent in such a way that the instrumentdeflection angle was 90°, and radius of curvature was 5 mm. Endodontic instruments were placed in the tubes so that their diameter at the point of maximum curvature was 0.3 mm. Rotation speed was 300 rpm. Time to fracture was recorded and converted to number of cycles for each instrument.

There was no significant difference in the mean number of cycles before fracture betweenPathFiles (198 cycles), FlexMaster (197 cycles) and Race (232 cycles). LightSpeed showed a significant increase in the mean number of cycles to failure (608 cycles) when compared to the tapered instruments (P < 0.05). Theprototype steel non-solid endodontic instrument reached significantly higher number of cycles before fracture (1315 cycles) when compared to all instruments (P < 0.05).

The new prototype non-solid steelendodontic instrument had better fatigue characteristics than several traditional solid nickel-titanium endodontic instruments. In addition, non-tapered solid nickel-titanium instrument had significantly higher fatigue resistancethan tapered solid nickel-titanium instruments of the same diameter.