Contemporary Root Canal Preparation Innovations in Biomechanics Ove Andreas Peters, DMD, MS, PhD a, *, Maria Guiomar de Azevedo Bahia, DDS, MS, PhD b , Erika Sales Joviano Pereira, DDS, MS, PhD c INTRODUCTION Engine-driven instrumentation is a mainstay in root canal therapy as it serves the goal of canal shaping while reducing the number of procedural errors. 1,2 The last decade in instrument development can be characterized by several key strategies:  The use of more flexible alloys, which not only promise better canal negotiation but also extended fatigue life Disclosures: Dr O.V. Peters serves as a consultant for Dentsply Tulsa Dental. Drs M.G. de Azevedo Bahia and E.S.J. Pereira deny any conflicts of interest. a Department of Endodontics, University of the Pacific Arthur A. Dugoni School of Dentistry, 155 5th Street, San Francisco, CA, USA; b Department of Restorative Dentistry, Faculty of Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil; c Department of Dental Clinic, School of Dentistry, Federal University of Bahia, Salvador, Bahia, Brazil * Corresponding author. E-mail address: opeters@pacific.edu KEYWORDS  Nickel titanium  Heat treatment  Glide path  Cyclic fatigue  Corrosion  Outcomes KEY POINTS  Instrument design: Current innovations include modifications in helical angle, taper, and lon- gitudinal shape as well as kinematics. The intended improvements are prevention of thread- ing in, less canal transportation, better canal wall preparation, and less fatigue accumulation.  Nickel titanium alloy: There is a trend toward more martensitic (ie, more flexible alloy mod- ifications), which is realized by varying heat treatment, specifically after grinding, so that the martensitic finish temperature for recent instruments is often greater than room temperature.  Testing methods: In the absence of clinical evidence, most information discerning current root canal preparation instruments stems from various in vitro experiments, notably assessment of canal transportation, cyclic fatigue, and corrosion. Dent Clin N Am 61 (2017) 37–58 http://dx.doi.org/10.1016/j.cden.2016.08.002 dental.theclinics.com 0011-8532/17/ª 2016 Elsevier Inc. All rights reserved.