Efficiency of fractured file retrieval according to different nickel-titanium alloys and fragment lengths

The fracture of nickel-titanium (NiTi) rotary files may be considered a direct cause of endodontic treatment failure. This study aimed to evaluate the effect of alloy type and fragment length on the efficiency of fractured file removal under standardized simulated conditions. Simulated J-shape canal blocks were shaped up to ProTaper Gold F2 size. The file tips of ProTaper Gold (PTG) F2 and ProTaper Universal (PTU) F2 files were artificially sectioned to make the fragments of 3-mm and 4-mm, respectively (n = 25 for each system and fragment length). The file fragments were positioned 1.5 mm coronally from the apical end of the simulated canal. The file fragments were retrieved using Gates-Glidden drills and ultrasonic instruments at a single optimized power setting. Retrieval time, defined as the duration from ultrasonic activation until fragment removal, was recorded. Statistical analysis evaluated the effects of alloy type and fragment length with a significance level of 95%. For 3-mm fragments, the PTU files demonstrated significantly faster retrieval times than the PTG files (p < 0.05). However, no significant difference in retrieval time was found between PTG and PTU files for 4-mm fragments. Regardless of the file alloy types, the 3-mm fragments were removed in a significantly shorter time than the 4-mm fragments (p < 0.05). Under controlled resin model conditions, both fragment length and alloy type significantly influence fractured NiTi file retrieval efficiency.