Influence of heat-treated Ni-Ti rotary files and irrigant type on the accuracy of integrated apex locators: An in vitro study

Purpose: This study investigated the effect of different nickel–titanium file systems and irrigation protocols on the accuracy of working length measurements during root canal preparation.
Methods: A total of 72 extracted mandibular central incisors were decoronated at 18 mm. Actual lengths (AL) were determined using a hand file and digital caliper under a microscope. Teeth were divided into four main groups based on irrigation solution, and then into two subgroups by file system: 2.5% or 5% NaOCl with/without 9% HEDP, combined with either WaveOne Gold(WOG) or WaveOne(WO). Root canals were shaped using WOG or WO files with a VDW Gold Reciproc motor in an alginate model simulating the oral environment, following the respective irrigation protocol. Electronic lengths (EL) were determined using an integrated electronic apex locator. EL–AL differences were calculated and analyzed using Kruskal-Wallis and Mann-Whitney U tests (p<0.05).
Results: No significant differences in EL–AL values were observed among the main irrigation solution groups or between files with different heat treatments (p>0.05). All tested conditions showed clinically acceptable accuracy.
Conclusion: These findings suggest that the type of file system and irrigation solution, including continuous chelation, do not compromise the reliability of EL determination during endodontic treatment.

Keywords: Chelating agents, endodontics, nickel-titanium, root canal preparation; sodium hypochlorite.