dental materials 25 ( 2 0 0 9 ) 1221–1229 available at www.sciencedirect.com journal homepage: www.intl.elsevierhealth.com/journals/dema Micro-XRD and temperature-modulated DSC investigation of nickel–titanium rotary endodontic instruments  Satish B. Alapati a,1 , William A. Brantley b,∗ , Masahiro Iijima c , Scott R. Schricker b , John M. Nusstein d , Uei-Ming Li e , Timothy A. Svec f a Formerly Department of Materials Science, College of Dental Medicine, Medical University of South Carolina, Charleston, SC, USA b Division of Restorative and Prosthetic Dentistry, College of Dentistry, The Ohio State University, Mailbox #191, PO Box 182357, 305 West 12th Avenue, Columbus, OH 43218-2357, USA c Division of Orthodontics and Dentofacial Orthopedics, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Japan d Division of Endodontics, College of Dentistry, The Ohio State University, Columbus, OH, USA e College of Medicine, National Taiwan University and Cardinal Tien Hospital, Taipei, Taiwan f Department of Endodontics, School of Dentistry, Oregon Health & Science University, Portland, OR, USA article info Article history: Received 8 November 2008 Received in revised form 10 April 2009 Accepted 20 April 2009 Keywords: Nickel–titanium Endodontics Rotary instrument X-ray diffraction Differential scanning calorimetry Heat treatment Phase transformation Wrought alloys Metallurgy Superelasticity abstract Objectives. Employ Micro-X-ray diffraction and temperature-modulated differential scanning calorimetry to investigate microstructural phases, phase transformations, and effects of heat treatment for rotary nickel–titanium instruments. Methods. Representative as-received and clinically used ProFile GT and ProTaper instruments were principally studied. Micro-XRD analyses (Cu K X-rays) were performed at 25 ◦ C on areas of approximately 50 m diameter near the tip and up to 9 mm from the tip. TMDSC analyses were performed from -80 to 100 ◦ C and back to -80 ◦ C on segments cut from instru- ments, using a linear heating and cooling rate of 2 ◦ C/min, sinusoidal oscillation of 0.318 ◦ C, and period of 60 s. Instruments were also heat treated 15 min in a nitrogen atmosphere at 400, 500, 600 and 850 ◦ C, and analyzed. Results. At all Micro-XRD analysis regions the strongest peak occurred near 42 ◦ , indicat- ing that instruments were mostly austenite, with perhaps some R-phase and martensite. Tip and adjacent regions had smallest peak intensities, indicative of greater work hard- ening, and the intensity at other sites depended on the instrument. TMDSC heating and cooling curves had single peaks for transformations between martensite and austenite. Austenite-finish (A f ) temperatures and enthalpy changes were similar for as-received and used instruments. Heat treatments at 400, 500 and 600 ◦ C raised the A f temperature to 45–50 ◦ C, and heat treatment at 850 ◦ C caused drastic changes in transformation behavior. Significance. Micro-XRD provides novel information about NiTi phases at different positions on instruments. TMDSC indicates that heat treatment might yield instruments with sub- stantial martensite and improved clinical performance. © 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.  Based upon a portion of a dissertation submitted by the first author to the Graduate School of The Ohio State University, in partial fulfillment of the requirements for the degree Doctor of Philosophy. ∗ Corresponding author. Tel.: +1 614 292 0773; fax: +1 614 292 9422. E-mail addresses: wbrantle@columbus.rr.com, brantley.1@osu.edu (W.A. Brantley). 1 Present address: Department of Endodontics, College of Dentistry, University of Illinois at Chicago, Chicago, IL, USA. 0109-5641/$ – see front matter © 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.dental.2009.04.010