Abstract
Aim: To review the reported defect and fracture rates of various NiTi instrumentation systems and identify factors that may influence the chance of NiTi file separation clinically.Data Sources: PubMed, EMBASE, and SCOPUS with controlled vocabulary and keywords in various combinations to identify articles that reported on the defects and/or fracture of NiTi instrument used clinically (Jan 1980 till Aug 2021), with additional search manually by going through the list of references of the initially screened articles. Those satisfying the inclusion and exclusion criteria were entered into the analysis.Study Eligibility Criteria, Participants, and Interventions: All studies from the said databases reporting on NiTi root canal instruments that were deformed or separated during normal clinical use.Study Appraisal and Synthesis Methods: Studies with data available and suitable for meta-analysis were grouped according to the general design of the NiTi instruments for comparison. Safety quotient value was calculated based on the rate of instrument distortion and fracture.Results: Various instrument designs exhibited different incidences of distortion and fracture, hence a different “safety quotient” (ratio of the amount of deformed instruments to that of fractures in use). Heat-treated files showed the highest safety quotient value. All brands of NiTi file demonstrated a statistically significantly lower incidence of fracture, if treated as disposable instruments after clinical use in a patient.Limitations: Inclusion of articles written in English only, and grouping of file systems into general design types in the analysis.Conclusions and Implications of Key Findings: NiTi endodontic files should be scrutinized for defects before being used in the root canal. Disposing the NiTi instruments after clinical use in a patient (so-called “single use”) is recommended for minimizing fracture clinically. Certain instrument designs tend to show discernible deformation before they should fracture in the next use.
Highlights
Nickel-titanium (NiTi) instruments have revolutionized the process of root canal shaping for non-surgical endodontic treatment since its commercial introduction in early 1990’s
The keywords and Boolean operators used in search are the same with each database: AND (NiTi OR Ni-Ti OR nickel titanium OR nickel-titanium) AND clinical AND
Widespread acceptance of NiTi instruments is hampered by the fear of their “unexpected” separation in the root canal
Summary
Nickel-titanium (NiTi) instruments have revolutionized the process of root canal shaping for non-surgical endodontic treatment since its commercial introduction in early 1990’s. The early brands were made of austenitic NiTi alloy that exhibits superelastic property [1]. Compared with conventional stainless steel files, they are able to enlarge the root canals expeditiously while respecting the root canal curvature [2]. NiTi files are available in many different designs, including different (non-ISO) size convention, increased body taper, and both regular and irregular cross sections. In the past few years, instruments made of martensitic NiTi were introduced by many manufacturers, with some making use of the shape memory property of the NiTi alloy. These heat-treated variants have been promulgated with claims for improved efficiency and greater instrument safety [4]
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