Abstract
Since there are no reviews of the literature on this theme, the aim of this narrative review is to summarize the metallurgical tests used in endodontics, pointing out their functional use and their pros and cons and giving readers a user-friendly guide to serve as an orientation aid in the plethora of metallurgical tests. With this purpose, a literature search for articles published between January 2001 and December 2021 was conducted, using the electronic database PubMed to collect all published articles regarding the metallurgical tests used in endodontics for the evaluation of NiTi rotary instruments. The search was conducted using the following keywords: “metallurgy”, “differential scanning calorimetry” (DSC), “X-ray diffraction” (XRD), “atomic force microscopy” (AFM), “energy-dispersive X-ray spectroscopy” (EDS), “focused ion beam analysis” (FIB) and “Auger electron spectroscopy” (AES) combined with the term “endodontics” or “NiTi rotary instruments”. Considering the inclusion and exclusion criteria, of the 248 articles found, only 81 were included in the narrative review. According to the results, more than 50% of the selected articles were published in one of the two most relevant journals in endodontics: International Endodontic Journal (22.2%) and Journal of Endodontics (29.6%). The most popular metallurgical test was DSC, with 43 related articles, followed by EDS (33 articles), AFM (22 articles) and XRD (21 articles). Few studies were conducted using other tests such as FIB (2 articles), micro-Raman spectroscopy (4 articles), metallographic analysis (7 articles) and Auger electron spectroscopy (2 articles).
Highlights
It could be stated that the modern era of endodontics began after the introduction of the nickel–titanium (NiTi) alloy as the material of choice for the manufacturing of endodontic instruments [1]
The metallurgical investigation of NiTi rotary instruments is fundamental for an in-depth comprehension of their mechanical properties, and it allows clinicians, researchers and engineers to understand the chemo-physical rationale behind certain mechanical behaviors of endodontic instruments, improving knowledge on this theme
Despite the importance of metallurgical tests in endodontics, to date there are no reviews of the literature on this topic, despite the fact that in recent years it has increasingly captured the attention of researchers. The aim of this narrative review was to summarize the metallurgical tests used in endodontics, pointing out their functional use, their pros and cons and the future perspectives, in order to offer readers a user-friendly guide to navigating the topic of endodontic metallurgy with ease, since this field may be tricky to understand for endodontists
Summary
It could be stated that the modern era of endodontics began after the introduction of the nickel–titanium (NiTi) alloy as the material of choice for the manufacturing of endodontic instruments [1]. The widespread use of NiTi rotary instruments, which have almost completely replaced stainless-steel (SS) manual instruments, fundamentally arose from the two most characteristic features of NiTi alloy: superelasticity and the shape memory effect. The former is defined as the ability of the alloy to store stress up to 8% without being plastically deformed, remaining in the elastic region of deformation by the creation of a stress-induced phase, called stress-induced martensite (SIM) [4,5]. The latter allows NiTi alloy to “memorize” a pre-imposed form and to return to it on heating, as a consequence of the transition from the martensitic crystallographic phase to the austenitic phase [6,7]. 4.0/).
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