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An investigation of phase transformation mechanisms for nickel-titanium rotary endodontic instruments

Alapati, Satish B
http://rave.ohiolink.edu/etdc/view?acc_num=osu1140186903

Abstract Details

2006, Doctor of Philosophy, Ohio State University, Dentistry.
Nickel-titanium rotary instruments based upon the intermetallic compound NiTi have gained considerable popularity among endodontists because the very low elastic modulus of NiTi enables these instruments to readily negotiate curved root canals during endodontic therapy with a slow-speed handpiece. However, concern about in vivo separation (fracture) of nickel-titanium instruments during treatment is still a major challenge confronting every manufacturer and endodontist, since this often happens without prior warning signs from permanent deformation. NiTi exists in two major microstructural phases: austenite, and martensite. Transformations between these NiTi phases occur rapidly by twinning on the atomic level and are reversible for stresses below the onset of permanent deformation. An intermediate R–phase is also sometimes observed for the transformation between austenite and martensite. The nickel-titanium rotary instruments are intentionally manufactured in the superelastic condition having the fully austenitic structure, which provides the capability of accommodating extensive elastic strain without fracture under clinical conditions associated with conventional root canal therapy. The overall objective of this study was to gain new insight into the microstructural phases in commercial NiTi rotary instruments and their transformations, which would be of scientific importance for development of new instruments with improved clinical performance. The phases present were identified by Micro-XRD (micro-x-ray diffraction) and TMDSC (temperature-modulated differential scanning calorimetry), using clinically popular ProFile GT and ProTaper nickel-titanium rotary instruments, which have two different cross-sectional designs. Instruments were analyzed in the as-received condition, after clinical use, and following elevated-temperature heat treatments. The first null hypothesis was that microstructural phases and phase transformations do not have an impact on clinical performance and instrument failure. The second null hypothesis was that appropriate heat treatments previously used for orthodontic wires would not result in beneficial changes in microstructural phases that may significantly affect the clinical life of these instruments. Based upon the present research and complimentary previous studies by this investigator, both null hypotheses were rejected. Information obtained from this research should aid future development of improved instruments with reduced likelihood of failure during clinical use.
William Brantley (Advisor)
Health Sciences, Dentistry
nickel-titanium rotary endodontic instruments; root canal preparation instruments; micro x-ray diffraction; temperature-modulated differential scanning calorimetry; heat treatment of NiTi rotary endodontic instruments

Recommended Citations

Citations

  • Alapati, S. B. (2006). An investigation of phase transformation mechanisms for nickel-titanium rotary endodontic instruments [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1140186903

    APA Style (7th edition)

  • Alapati, Satish. An investigation of phase transformation mechanisms for nickel-titanium rotary endodontic instruments. 2006. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1140186903.

    MLA Style (8th edition)

  • Alapati, Satish. "An investigation of phase transformation mechanisms for nickel-titanium rotary endodontic instruments." Doctoral dissertation, Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1140186903

    Chicago Manual of Style (17th edition)

osu1140186903
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© 2006, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.