Comparing The Difference in Cyclic Fatigue Resistance of Three different Rotary Ni-Ti instruments in Rotation and Reciprocation motion

Abstract

The purpose of the present study was to compare the cyclic fatigue resistance of three different nickel titanium instruments (Protaper Next, Twisted file and NRT files ) in rotation and reciprocation motion. Sixty rotary files were used in this study. They were classified into the following groups: Group A: Protaper Next Ni-Ti files (20files). Group B: Twisted File Ni-Ti files (20 files). Group C: NRT Ni-Ti files (20 files). All files have tip size ISO 25 and taper 0.06. Each group was further subdivided into two equal sub-groups according to the type of motion into: Subgroup 1: Rotation motion following manufacturer’s instructions. Subgroup 2: Reciprocation motion according to the geometry of file’s cross section. A custom made aluminum cyclic fatigue testing apparatus was especially designed for this study and a specially fabricated metal block made of stainless steel was used in this test. All instruments used in this study are of the same tip size and taper. The metal block contains a an artificial canal 2mm in depth that was designed to accommodate all instruments in terms of size and taper, thus providing the instrument with a suitable trajectory. The artificial canal was designed with 60 degree curvature and 5mm radius. The instruments were activated in rotation and reciprocation movements inside artificial canal till fracture occurred and the time of fracture was recorded. Means and standard deviations of time to fracture were calculated for each system and data was subjected to 2 way anova (p<0.05).