Evaluation of Success Rate of Endodontic Treatment Performed by Students with Stainless-Steel K–Files and Nickel–Titanium Hand Files

A previous study by our group found nickel-titanium (NiTi) 0.02 hand files maintained the original canal shape better than similar stainless-steel K-files (SS-K). Inexperienced dental students used both file types on molar teeth. The purpose of this study was to compare the 1-yr success rate of endodontic treatment of the same teeth used in our previous study. Twelve-month follow-up radiographs were compared with the immediate follow-up radiographs. Both sets of radiographs were taken with the same customized stent. Quantification of osseous changes using digital imaging was used. Thus, a reliable numerical estimation (densitometric ratio) of disease and healing processes could be established. Sixty-seven percent of the patients returned for the 12-month radiographs (19 NiTi vs. 21 SS-K). Immediate postoperative periapical status was found to be similar (p > 0.05). Teeth instrumented with the NiTi files demonstrated a higher mean change in densitometric ratio, compared with SS-K files (p < 0.05). Further tests of success (values: > or =0) and failure (value: < or =0) with the Fisher exact test showed more success (decreasing radiographic density) with NiTi files and more failures (increasing radiographic density) with SS-K type files (p < or = 0.03). This study indicates that maintaining the original canal shape after instrumentation leads to a better prognosis of endodontic treatment.