The introduction of automated instrumentation in endodontics represented a major advance in progress for this specialty, with improvements in the quality and predictability of root canal preparation and a significant reduction in procedural errors. In recent years, endodontic instruments have undergone a series of changes brought about by modifications in design, surface treatments, and thermal treatments. In addition, new movements have also been incorporated to offer greater safety and efficiency, optimizing the properties of the NiTi alloy, especially through eccentric rotary motion. An understanding of the mechanical properties of these new NiTi instruments and their effect on the clinical performance of root canal preparation is essential if dental practitioners are to select the instruments that provide optimal clinical outcomes, especially in curved or flattened canals. The objective of this literature review is to present and discuss the characteristics of the NiTi alloys used in the major instrumentation systems available in the market, as well as the influence of the metallurgical and mechanical properties of NiTi instruments and the movements that drive them, to enable more accurate and predictable planning of root canal preparation.

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AimTo compare the shaping ability of four instrumentation systems in curved molar root canals, using computerized microtomography (micro‐CT).MethodologyForty mesial roots of mandibular molars were submitted first to radiographic examination to determine their curvature and then to a micro‐CT scan to analyse other initial morphological characteristics. The specimens were distributed into four experimental groups, according to the endodontic instrumentation system used (n = 10): Group R, Reciproc; Group PTN, ProTaper Next; Group WOG, WaveOne Gold; Group PDL, ProDesign Logic. After root canal instrumentation, the specimens were submitted to a second micro‐CT scan, and the pre‐ and postoperative data were examined to evaluate the following parameters: volume of dentine removed (DR), increase in root canal volume (VI), untouched root canal surface area (UA), volume of accumulated hard tissue debris (AD) and structure model index (SMI). The data observed for these parameters after instrumentation were analysed using generalized linear models. R software was used for the analyses, and the level of significance adopted was 5%.ResultsThere were no significant differences among the instrumentation systems regarding the DR, VI, UA and AD parameters (P > 0.05). PTN and WOG systems were associated with greater increases in SMI than the PDL system (P < 0.05).ConclusionsThe four systems evaluated were similar regarding the parameters analysed, with the exception of the SMI, with the rate of variation of this parameter being greater after using the PTN and WOG systems than after using the PDL system. These results indicate that the four systems perform similarly in terms of their shaping ability, but that the PTN and WOG systems produced more rounded preparations than the PDL system.

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