Instrument separation(IS) is one of the possible complications during endodontic treatment. A separated instrument may serve as an obstacle in root canal preparation and cleaning, which may compromise the outcome and even result in treatment failure. At present, practitioners are still debating on how to avoid IS. Treatment decisions should be based on the evaluation of the effect of a separated instrument in situ on the result of the treatment and the risk of damage when retrieval is performed. Recent studies on the effect of IS on endodontic treatment prognosis are reviewed in this paper.
