The investigation of ultrasound efficacy in cleaning the surface of new endodontic instruments

Abstract

Introduction. Active parts and tips of various new stainless steel and nickel-titanium endodontic instruments can be coated with fragments or metal residues, which can become detached during endodontic treatment. These fragments may obstruct the root canals or even reach the periapical tissue during biomechanical preparation and should be removed before clinical use. Objective. The aim of this study was to evaluate the presence of metal residues on both new stainless steel and nickel-titanium endodontic instruments, and to determine the cleaning efficacy of ultrasound using distilled water or disinfectant solution for removing these residues. Methods. Forty-eight stainless steel and nickel-titanium instruments were carefully removed from their original packages with dental tweezers, in order to avoid any contact with the cutting flutes and tips. The instruments were evaluated in term of metal debris presence, using scanning electron microscopy (SEM) and x-ray energy-dispersive spectroscopy (EDS). The instruments were then removed from the electron microscopy analysis stubs and placed in an ultrasonic bath for 15 minutes at a frequency of 28 kHz, using distilled water or disinfectant solution. The surfaces of the instruments were re-evaluated after cleaning. Results. Before ultrasound cleaning, a larger amount of metal debris was observed on the nickel-titanium endodontic instruments when compared to those made of stainless steel. The presence of metal particles on the instruments was evaluated by using EDS analysis. The use of ultrasound was effective in removing the metal residues from both types of endodontic instrument surfaces. Conclusion. The use of ultrasound proved to be an efficient method for the removal of metal particles from the surface of new stainless steel and nickel-titanium endodontic instruments.