Comparison of Air Driven Handpiece and Electromotor on Distortion or Fracture Rate of Nickel Titanium Rotary Instruments

Statement of Problem: One of the affecting factors in adverse prognosis of root canal therapy is procedural accidents as broken files, facing with difficulty in removing. Many manufacturers have designed and marketed various electromotors with the ability of controlling rotational speed and torque. On the other hand, these expensive motors have encouraged other manufacturers to marketing different air driven handpieces. Despite of presenting various vast instruments for this purpose, only limited comparative studies have been carried out between electromotor and air driven handpiece. The purpose of this study was to evaluate the effect of air driven handpiece versus electromotor on distortion or fracture rate of NiTi rotary files. This in vitro randomized controlled trial was carried out on 160 canals of human’s matured molars with mild curvature (15-33o). After initial preparation of samples and considering the inclusion criteria, in the first group, preparation was carried out with air driven handpiece and in groups 2 Endo IT (VDW, Germany) was used as electromotor. In both groups Mtwo files with crown down technique were used for canal preparations. Data on file distortion or fracture were collected and analyzed using Mann Whitney, Mantel Cox, Kaplan-meiere and T tests. No significant differences on distortion or fracture rate of files between the two groups were found (p>0.05). Based on survival analysis safety probability of files after preparation of 9 canals was %64.1 in group 1 and %69.9 in group 2. There was no significant differences between this safety probability in the two groups (P=0.272). These findings showed that both electromotor and air driven handpiece has nearly similar effect on fracture rate or distortion of NiTi rotatory instruments.