EditorialEndodontic InstrumentsYA SHEN, GUEST EDITOR

The last two decades have seen an explosion inthe development of new nickel–titanium (NiTi)endodontic instrument materials and systems for rootcanal instrumentation, and tremendous achievementsand progress have been made in this sector of theendodontic discipline. NiTi rotary files are available ina variety of designs, each with features that affect themanner in which they engage and cut dentin andthe stress that may be generated within them.Increasing numbers of NiTi rotary instruments ofvarious designs are now being marketed; newinstruments and materials seem to appear faster thanclinicians can learn about the preceding versions. Thishas created an educational challenge for practitioners,universities, and manufacturers, requiring a greaterdegree of cooperation amongst these groups thanever before. Clinicians should use only thoseinstruments and materials shown to be safe andeffective in independent studies. Our knowledgeand understanding of instruments as well as therecommendations for clinical protocols are based onboth clinical experience and the results of past andongoing research.

This volume of Endodontic Topics focuses on NiTiinstruments. In addition, a review of ultrasonicendodontic instruments has been included. The topicsselected reflect the need for a better understanding ofsome of the key areas of instruments. First-generationNiTi rotary instruments, which came to market in1992, relied much on the superelasticity of the metal,while the emphasis in instrument design was onmaximized safety rather than cutting effectiveness.Since then the focus has shifted to new manufacturingprocesses (thermomechanical treatment and R-phase)and different unique features such as a variable cross-section along the length of the active portion of theinstrument. In the first article, Markus Haapasalo and

Ya Shen summarize the metallurgical and mechanicalproperties of NiTi endodontic instruments and thedesign features of each generation, with a special focuson the latest generation of NiTi instruments.

Despite the advertising claims of superiority ofdesign for some NiTi rotary systems, few have beensupported by objective well-designed studies in theliterature. A variety of models and methods have beenused to investigate the properties and behavior of NiTiinstruments. In the second article, Ya Shen and GaryCheung review and discuss the methods and modelsto study NiTi instruments. Traditional models arecritically evaluated and new methods and models arepresented, together with a discussion of their benefitsand limitations. We are sure that this review article willhelp colleagues to better evaluate existing instrumentresearch and also provide support to students ingraduate endodontic programs for planning researchprojects on instruments.

NiTi alloy has been used as the raw material formaking endodontic files for two decades. The interestin NiTi instrument research has not waned withtime. In fact, there is a renewed interest in thisfield, notably through the application of modernresearch tools and techniques from other fields,making it a truly cross-disciplinary area of research.Differences in mechanical properties betweenendodontic instruments might be related to thechemical composition, phase constitution, orfabrication process of NiTi instruments. In the thirdarticle, Huimin Zhou, Bin Peng, and Yu-Feng Zhengreview the mechanical properties of the traditionalsuperelastic NiTi instruments and currently developednovel NiTi instruments, as well as their internal andexternal influencing factors, with a special focuson the influence of metallurgical properties on theirmechanical properties.

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Endodontic Topics 2013, 29, 1–2All rights reserved

© 2013 John Wiley & Sons A/S.Published by John Wiley & Sons Ltd

ENDODONTIC TOPICS1601-1538

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The endodontic literature presents a large body ofexperimental evidence that root canal preparationand disinfection exert unfavorable effects onto rootdentin. Clinical evidence for the significance of theseeffects is missing. In the fourth article, MichaelHülsmann describes the present knowledge on theeffects of mechanical instrumentation and chemicalirrigation on the root canal dentin and surroundingtissues.

Effective cleaning of root canals requires mechanicalinstrumentation combined with irrigation. Recently, anew concept of mechanical instrumentation wasintroduced to allow effective cleaning while avoidingexcessive removal of sound dentin, which potentiallycould lead to minimally invasive endodontictreatment. In the fifth article, Zvi Metzger, MichaelSolomonov, and Anda Kfir review the targets andchallenges for effective cleaning of root canals and themeans for evaluating the cleaning efficacy. They alsoevaluate the role of mechanical instrumentation ineffectively cleaning root canals.

Despite the introduction of flexible NiTiinstruments and torque-limited devices, root canalpreparation of severely curved canals is still challengingand canals may be transported and/or other

procedural errors may occur during preparationprocedures. There are several aspects that influence theperformance of root canal instruments with respectto their shaping ability. In the sixth article, SebastianBürklein and Edgar Schäfer elucidate differentparameters that have an impact on canal transportationand discuss the impact of canal transportation ontreatment outcomes.

The piezoelectric ultrasonic device has the potentialto be routinely incorporated into almost every phaseof endodontic treatment, re-treatment, and apicalmicrosurgery. It is already indispensable as a precisetool in many of the most challenging clinicalsituations. In the last article, Ellen Park describes theevolution and various applications of ultrasound indentistry, examines in detail the ultrasonic tools thathave been developed for endodontic purposes, andalso describes the use of ultrasonics during specificendodontic procedures.

We are extremely grateful to the authors for theircontributions to this issue of Endodontic Topics. We areconvinced that the material presented here will providethe readership with an up-to-date and comprehensiveappraisal of one of the most challenging aspects ofEndodontics today.

Shen

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