The Journal of Contemporary Dental Practice
Volume 22 | Issue 6 | Year 2021

New Strategies and Instruments for Root Canal Shaping Procedure: An Overview

Massimo Giovarruscio1, Edit Khajanka2, Almira Isufi3, Maya Feghali4, Luciano Pacifici5, Orlando Donfrancesco6, Shilpa Bhandi7, Andrea Pacifici8, Federico Valenti Obino9

1Department of Endodontics, Faculty of Dentistry, Oral and Craniofacial Sciences, Guy’s Dental Hospital, London, UK; Institute of Dentistry, IM. Sechenov First Moscow State Medical University, Moscow, Russia

2Department of Dental Medicine, Medical University of Tirana, Tirana, Albania

3,5,8,9Department of Oral and Maxillo-Facial Sciences, Sapienza University of Rome, Rome, Italy

4Department of Restorative and Aesthetic Dentistry, Lebanese University and Endodontics, Beirut, Lebanon

6Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Sapienza University of Rome, Rome, Italy

7Department of Restorative Dental Science, Jazan University, Jazan, Saudi Arabia

Corresponding Author: Orlando Donfrancesco, Department of Anatomy, Histology, Forensic Medicine and Orthopaedics, Sapienza University of Rome, Rome, Italy, e-mail: orlando.donfrancesco@uniroma1.it

How to cite this article: Giovarruscio M, Khajanka E, Isufi A, et al. New Strategies and Instruments for Root Canal Shaping Procedure: An Overview. J Contemp Dent Pract 2021;22(6):597–598.

Source of support: Nil

Conflict of interest: None


Cone-beam computed tomography-based three-dimensional analysis of root canal trajectories and shapes have clearly shown that root canals are more complex in 3D, compared to traditional 2D visualization,14 and consequently, these findings affect properties of the nickel–titanium (NiTi) files requiring the following factors:

Cleaning is obviously related to proper use of irrigants and irrigation techniques, but instruments also play a significant role to create more or less debris, remove them properly, vehicle the solutions and disrupt biofilm, and create a proper shape for obturation avoiding under- and over-instrumentation.58

Improving properties of NiTi files can be done mainly in three different ways as follows:

The last option has recently become the most important feature to significantly improve flexibility and fracture resistance of the NiTi rotary files.1316

In the first 20 years after the introduction of NiTi alloy in endodontics, all instruments have been superelastic, austenitic files. The superior properties of the alloy, compared to traditional stainless steel, were considered a huge advantage and allowed the clinical use of files of greater tapers in continuous rotation. However, such an increase of instruments dimensions and the greater stress induced by the motion resulted, especially for bigger sizes and tapers, in quite rigid instruments for the purpose and increased risk of failure, especially in complex curvatures.14,15

NiTi is a “delicate” alloy, very sensible to heat, and during the manufacturing process, the alloy is weakened by the grinding wheels that design the flutes and the geometry of the file, both externally and internally. External defects can be partially adjusted by electropolishing,9 while internal defects can be partially adjusted by specific heat treatments after the manufacturing process. Heat treatments can vary a lot and each manufacturer has its own proprietary, undisclosed one. Generally speaking, all heat treatments can improve flexibility and fracture resistance to a certain effect, but there are huge differences in how they are performed and the resulting effects.14

Some companies, i.e., Edge Endo, have invested a lot in research to produce better heat treatments, which have become probably the most important manufacturing treatment to improve the mechanical properties of the instruments. For instance, changes in design could increase flexibility and resistance by 20–30%, while FireWire heat treatment (EdgeEndo) has been shown to increase flexibility up to three times (300%) and even more the fatigue resistance.1417 These new heat-treated files can also exhibit different shape memory effects and therefore are defined martensitic NiTi files: they can be precurved, if needed, and produce less bounce back, allowing easier negotiation and less canal transportation. These improvements have significantly changed clinical procedures, because such a difference between austenitic and martensitic files (some manufacturers provide the same file in the two versions, i.e. EdgeTaper and EdgeTaper Platinum) is currently modifying our clinical approach to instrumentation, depending on which type of instruments we are using. Martensitic files are ideal for minimally invasive endodontics and management of complex curvatures because they can more easily negotiate canal with less iatrogenic errors due to less bounce back, more flexibility, and resistance to bending stresses.1719 Moreover, they are less sensitive to interferences and can be precurved, making it easier to negotiate divergent canals, hidden curvature, and ledges.

Minimally invasive is obviously a trend, since we know that any endodontic treatment to a certain extent can weaken a tooth, and tooth fracture is the main cause for long-term failures (even if it depends probably slightly more on the quality and type of postendodontic restorations). However, when treating complex root canals, we should always make some compromise between the tendency to be more conservative2022 and the risk that poor access cavity design, or coronal flaring, may create interferences that lead to iatrogenic errors, such as canal transportation or intracanal breakage.


1. Gambarini G, Ropini P, Piasecki L, et al. A preliminary assessment of a new dedicated endodontic software for use with CBCT images to evaluate the canal complexity of mandibular molars. Int Endod J 2018;51(3):259–268. DOI: 10.1111/iej.12845.

2. Tonini R, Xhajanka E, Giovarruscio M, et al. Print and try technique: 3D-printing of teeth with complex anatomy a novel endodontic approach. Appl Sci 2021;11(4):1511. DOI: 10.3390/app11041511.

3. Quero L, Schianchi G, Obino FV, et al. Root canal morphology of lower lateral incisors: a CBCT in vivo study. Morfologia del sistema endodontico negli incisivi inferiori: Uno studio in vivo attraverso la tomografia computerizzata Cone Beam. Giornale Ital Endod 2020;34(1):41–46. DOI: 10.32067/GIE.2020.34.01.14.

4. Reda R, Zanza A, Mazzoni A, et al. An update of the possible applications of magnetic resonance imaging (MRI) in dentistry: a literature review. J. Imaging 2021;7:75. DOI: 10.3390/jimaging7050075.

5. Gambarini G, Testarelli L, Pongione G, et al. Radiographic and rheological properties of a new endodontic sealer. Aust Endod J 2006;32(1):31–34. DOI: 10.1111/j.1747-4477.2006.00005.x.

6. Piasecki L, Carneiro E, da Silva Neto UX, et al. The use of micro-computed tomography to determine the accuracy of 2 electronic apex locators and anatomic variations affecting their precision. J Endod 2016;42(8):1263–1267. DOI: 10.1016/j.joen.2016.04.024.

7. Turk T, Cicconetti A, Di Nardo D, et al. Nonsurgical retreatment using regenerative endodontic protocols: a case report. J Contemp Dent Pract 2020;21(11):1275–1278. DOI: 10.5005/jp-journals-10024-2909.

8. Mazzoni A, Pacifici A, Zanza A, et al. Assessment of real-time operative torque during nickel–titanium instrumentation with different lubricants. Appl Sci 2020;10:6201. DOI: 10.3390/app10186201.

9. Gambarini G, Testarelli L, Galli M, et al. The effect of a new finishing process on the torsional resistance of twisted nickel-titanium rotary instruments. Minerva Stomatol 2010;59(7–8):401–406.

10. Bhandi S, Seracchiani M, Donfrancesco O, et al. Nickel-titanium rotary instruments: an in vitro comparison. J Contemp Dent Pract 2021. DOI: 10.5005/jp-journals-10024-3081.

11. Gambarini G, Piasecki L, Miccoli G, et al. Classification and cyclic fatigue evaluation of new kinematics for endodontic instruments. Aust Endod J 2019;45(2):154–162. DOI: 10.1111/aej.12294.

12. Gambarini G, Seracchiani M, Piasecki L, et al. Measurement of torque generated during intracanal instrumentation in vivo. Int Endod J 2019;52(5):737–745. DOI: 10.1111/iej.13042.

13. Miccoli G, Cicconetti A, Gambarini G, et al. A new device to test the bending resistance of mechanical endodontic instruments Appl Sci 2020;10(20):7215. DOI: 10.3390/app10207215.

14. Gambarini G, Cicconetti A, Nardo DD, et al. Influence of different heat treatments on torsional and cyclic fatigue resistance of nickel-titanium rotary files: a comparative study. Appl Sci 2020;10(16):560. DOI: 10.3390/app10165604.

15. Seracchiani M, Miccoli G, Reda R, et al. A comprehensive in vitro comparison of mechanical properties of two rotary endodontic instruments. World J Dent 2020;11(3):185–188. DOI: 10.5005/jp-journals-10015-1729.

16. Gambarini G, Galli M, Di Nardo D, et al. Differences in cyclic fatigue lifespan between two different heat treated NiTi endodontic rotary instruments: WaveOne gold vs EdgeOne fire. J Clin Exp Dent 2019;11(7):e609–e613. DOI: 10.4317/jced.55839.

17. Grande NM, Plotino G, Silla E, et al. Environmental temperature drastically affects flexural fatigue resistance of nickel-titanium rotary files. J Endod 2017;43(7):1157–1160. DOI: 10.1016/j.joen.2017.01.040.

18. Seracchiani M, Miccoli G, Di Nardo D, et al. Effect of flexural stress on torsional resistance of NiTi instruments. J Endod 2021;47(3):472–476. DOI: 10.1016/j.joen.2020.10.011.

19. Di Nardo D, Gambarini G, Seracchiani M, et al. Influence of different cross- section on cyclic fatigue resistance of two nickel-titanium rotary instruments with same heat treatment: an in vitro study. Saudi Endod J 2020;10:221–225. DOI: 10.4103/sej.sej_124_19.

20. Gambarini G, Galli M, Morese A, et al. Precision of dynamic navigation to perform endodontic ultraconservative access cavities: a preliminary in vitro analysis. J Endod 2020;46(9):1286–1290. DOI: 10.1016/j.joen.2020.05.022.

21. Isufi A, Plotino G, Grande NM, et al. Standardization of endodontic access cavities based on 3-dimensional quantitative analysis of dentin and enamel removed. J Endod 2020;46(10):1495–1500. DOI: 10.1016/j.joen.2020.07.015.

22. Gambarini G, Seracchiani M, Zanza A, et al. Influence of shaft length on torsional behavior of endodontic nickel-titanium instruments. Odontology. 2020. DOI: 10.1007/s10266-020-00572-2.

© The Author(s). 2021 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted use, distribution, and non-commercial reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.