Influence of continuous or reciprocating motion on cyclic fatigue resistance of 4 different nickel-titanium rotary instruments

By Pedullà E, Grande NM, Plotino G, Gambarini G, Rapisarda E

Date: 01/2013
Journal: JOE

Summary:

Purpose: To evaluate the resistance to flexural fatigue of Reciproc R25, WaveOne Primary, Mtwo, &TF NiTi files used in continuous rotation and in 2 different reciprocating motions.

 N=  180 files (ie, Reciproc ,WaveOne , Mtwo and TF) were tested, (n=45) instruments for each brand were divided into 3 groups (n = 15) on the basis of the motion tested:

-continuous rotation (Gp 1: 300 rpm)

-reciprocal motion with the ‘‘RECIPROC ALL’’ mode (Gp 2)

-‘‘WAVEONE ALL’’ mode (Gp 3).

Materials/Methods:

  • A static model for cyclic fatigue testing was conducted in a custom-made device, instrument confined in an artificial curved canals, 60ocurve with a 5-mm radius.

  • Resistance to cyclic fatigue was determined by the number of cycles to failure (NCF) .

  • All instruments were rotated until a fracture occurred. A video recording was performed simultaneously.

Most highlighted Results:

1.Reciprocal motions were significantly higher in cyclic fatigue resistance compared with continuous rotation.

2.TF instruments had the best overall results, especially in reciprocating motion, followed by the Mtwo, Reciproc, & WaveOne.

3.The mean length of the fractured fragments of the 4 brands used did not show any statistical difference.

4.When used with appropriate clinical rotation, only WaveOne showed a lower fatigue resistance than the other brands

Clinical Significance:

Reciprocating motion is associated with a longer lifespan of the instruments regardless of the alloy used in manufacturing