Angular deflection of rotary nickel titanium files: a comparative study.

A new manufacturing method of twisting nickel titanium wire to produce rotary nickel titanium (RNT) files has recently been developed. The aim of the present study was to evaluate whether the new manufacturing process increased the angular deflection of RNT files, by comparing instruments produced using the new manufacturing method (Twisted Files) versus instruments produced with the traditional grinding process. Testing was performed on a total of 40 instruments of the following commercially available RNT files: Twisted Files (TF), Profile, K3 and M2 (NRT). All instruments tested had the same dimensions (taper 0.06 and tip size 25). Test procedures strictly followed ISO 3630-1. Data were collected and statistically analyzed by means ANOVA test. The results showed that TF demonstrated significantly higher average angular deflection levels (P<0.05), than RNT manufactured by a grinding process. Since angular deflection represent the amount of rotation (and consequently deformation) that a RNT file can withstand before torsional failure, such a significant improvement is a favorable property for the clinical use of the tested RNT files.