Broken Endodontic Instrument Removal Using Ultrasounds, Microscope and a Modified Spinal Needle

The fracture of an endodontic instrument is a frustrating phenomenon, both for practitioners and patients, that can compromise the cleaning and shaping procedures of the root canal treatment, with a potential impact on the treatment outcome. In the past decades, the advent of rotary nickel titanium instruments resulted in an increased incidence of instrument separation.

Two mechanisms have been reported in order to describe the fracture of an endodontic instrument inside the root canal: torsional stress and cyclic fatigue. Cyclic failure is due to the constant tension and compression which insists on the file when it shapes the maximal root canal curvature area. Torsional failure occurs when the tip of the instrument locks on the wall of the root canal while the shafts keeps rotating, and the torque exceeds the plastic limit of the metal.

Several studies focused on causes and factors influencing the weakening of endodontic instrument after clinical use, and some recommendation were given trying to minimized the risk of instruments breakage. Nevertheless, this problem can still occur, even to an experienced operator, making the achievement of a correct and predictable root canal final treatment uncertain.

Due to their complexity, many of these cases are approached by extraction and implant replacement of the so evaluated "hopeless" tooth. Treatment decisions can vary widely among dentists and dental specialists and may be based more on personal values and experience than an objective analysis of treatment benefits, risks, costs, prognosis, and alternatives.

At present, there is no standardized procedure for safe and consistently successful instrument fragment removal in the dental literature.