الفهرس 
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Abstract
Aim of study: This study was designed to evaluate” In vitro and clinical” success rate of removal of separated endodontic instrument using three different techniques: Ultrasonic tips (US), Instrument Removal System (IRS) and The File Extraction Probe Set (FXP). Materials and Methods: In the in vitro part, 135 human molars with closed apices were collected. One Shape rotary files (Micro-Mega, Besancon, France) 0.06 taper and size #25 were driven into the canal to be fractured in the curve. Angles of curvature were measured for all the canals with the separated instruments, and the teeth were divided into three main groups (n= 45) according to their curvature angles into slight, moderate, and severe. Each group were randomly divided into three subgroups (n=15) according to the technique used for removal of separated instrument either with US, IRS or FXP. In the clinical part of the study, 135 patients with separated instrument were divided into three main groups (n= 45) according to their curvature angles into slight, moderate, and severe. Each group were randomly divided into three subgroups (n=15) according to the technique used for removal of separated instrument either with US, IRS or FXP. All the separated instrument removal procedures were done with the use of dental operating microscope. The success rate of removal and the time of removal of each technique were evaluated.
Results: In the in vitro and clinical part, the US showed the highest success rate, followed by IRS. There was no statistically significant difference between US and IRS. The FXP showed the lowest success rate, which was significantly lower than the other 2 techniques. Conclusion: The use of the dental operating microscope is considered a very important armamentarium for separated instrument removal. The US showed to be the most successful technique among the used techniques in this study. FXP had the lowest success rate for separated instrument removal compared the other techniques.