Assessment of the Nickel Ion Releases from the Broken Stainless Steel and Nickel Titanium Endodontic Instruments

Abstract

Purpose: The purpose of this study was to assess the nickel ion releases from the broken stainless steel and nickel titanium endodontic instruments in a phosphate buffer solution at different time periods. Methods: Thirty-two extracted human mandibular premolars with mature apices, single canals and of similar lengths were selected for the study. #35.04 Mtwo and #35.02 K-files were used for this study. Thirty-two extracted human mandibular premolars were divided into two groups randomly (n: 16) according to material type of file (stainless steel or NiTi). These two groups were then divided into two subgroups: files located at the apical foramen level (n: 8) or 3 mm beyond the apical foramen (n: 8). The voltammetric experiments were carried out using a computer controlled electroanalysis system the Metrohm 757 VA Computrace Electrochemical Analyzer. Comparisons intragroup and intergroups were evaluated with Kruskal-Wallis H and Mann-Whitney U tests statistically. Results: No ion release was detected in both file groups at the apical foramen level (p>0.05). In 3 mm beyond from apical foramen group, stainless steel showed no ion release; nevertheless, NiTi files presented ion release (p<0.05). Evaluation of nickel ion release of NiTi files showed statistical difference regarding time intervals (p<0.05). Conclusion: It is concluded that removal of separated file in patients with history of nickel allergy, is important when separated file tip is 3 mm beyond the apical foramen because of possibility of nickel ion release.