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KJO Korean Journal of Orthodontics

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pISSN 2234-7518
eISSN 2005-372X

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Korean J Orthod   

First Published Date February 7, 2023

Copyright © The Korean Association of Orthodontists.

Thermo-mechanical properties in bending of a multizone nickel-titanium archwire: A retrieval analysis

Panagiotis Rouliasa, Ioulia-Maria Mylonopouloua, Iosif Sifakakisa, Christoph Bourauelb, Theodore Eliadesc

aDepartment of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
bDepartment of Oral Technology, School of Dentistry, University Hospital Bonn, Bonn, Germany
cClinic of Orthodontics and Paediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland

Correspondence to:Iosif Sifakakis.
Assistant Professor, Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, 2 Thibon str, 11527 Goudi, Athens, Greece.
Tel +302107461228 e-mail isifak@dent.uoa.gr

How to cite this article: Roulias P, Mylonopoulou IM, Sifakakis I, Bourauel C, Eliades T. Thermo-mechanical properties in bending of a multizone nickel-titanium archwire: A retrieval analysis. Korean J Orthod. Published online February 7, 2023. https://doi.org/10.4041/kjod22.183

Received: August 18, 2022; Revised: November 8, 2022; Accepted: November 16, 2022

Abstract

Objective: This study aimed to compare the mechanical and thermal properties in the anterior and posterior segments of new and retrieved specimens of a commercially available multizone superelastic nickel-titanium (NiTi) archwire. Methods: The following groups of 0.016 × 0.022-inch Bioforce NiTi archwires were compared: a) anterior and b) posterior segments of new specimens and c) anterior and d) posterior segments of retrieved specimens. Six specimens were evaluated in each group, by three-point bending and bend and free recovery tests. Bending moduli (Eb) were calculated. Furthermore, the new specimens were evaluated with scanning electron microscopy/energy-dispersive X-ray spectrometry. A multiple linear regression model with a random intercept at the wire level was applied for data analysis. Results: The forces in the posterior segments or new specimens were higher than those recorded in the anterior segments or retrieved specimens, respectively. Accordingly, Eb also varied. Higher austenite start and austenite finish (Af) temperatures were recorded in the anterior segments. No statistically significant differences were found for these temperatures between retrieved and new wires. The mean elemental composition was (weight percentage): Ni, 52.6 ± 0.5; Ti, 47.4 ± 0.5. Conclusions: The existence of multiple force zones was confirmed in new and retrieved Bioforce archwires. The retrieved archwires demonstrated lower forces during the initial stages of deactivation in three-point bending tests, compared with new specimens. The Af temperature of these archwires may lie higher than the regular intraoral temperature. Even at 2 mm deflections, the forces recorded from these archwires may lie beyond biologically safe limits.

Keywords: Archwire, Biomaterial science, Nitinol, Transformation temperature

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Korean J Orthod   

First Published Date February 7, 2023

Copyright © The Korean Association of Orthodontists.

Thermo-mechanical properties in bending of a multizone nickel-titanium archwire: A retrieval analysis

Panagiotis Rouliasa, Ioulia-Maria Mylonopouloua, Iosif Sifakakisa, Christoph Bourauelb, Theodore Eliadesc

aDepartment of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
bDepartment of Oral Technology, School of Dentistry, University Hospital Bonn, Bonn, Germany
cClinic of Orthodontics and Paediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland

Correspondence to:Iosif Sifakakis.
Assistant Professor, Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, 2 Thibon str, 11527 Goudi, Athens, Greece.
Tel +302107461228 e-mail isifak@dent.uoa.gr

How to cite this article: Roulias P, Mylonopoulou IM, Sifakakis I, Bourauel C, Eliades T. Thermo-mechanical properties in bending of a multizone nickel-titanium archwire: A retrieval analysis. Korean J Orthod. Published online February 7, 2023. https://doi.org/10.4041/kjod22.183

Received: August 18, 2022; Revised: November 8, 2022; Accepted: November 16, 2022

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective: This study aimed to compare the mechanical and thermal properties in the anterior and posterior segments of new and retrieved specimens of a commercially available multizone superelastic nickel-titanium (NiTi) archwire. Methods: The following groups of 0.016 × 0.022-inch Bioforce NiTi archwires were compared: a) anterior and b) posterior segments of new specimens and c) anterior and d) posterior segments of retrieved specimens. Six specimens were evaluated in each group, by three-point bending and bend and free recovery tests. Bending moduli (Eb) were calculated. Furthermore, the new specimens were evaluated with scanning electron microscopy/energy-dispersive X-ray spectrometry. A multiple linear regression model with a random intercept at the wire level was applied for data analysis. Results: The forces in the posterior segments or new specimens were higher than those recorded in the anterior segments or retrieved specimens, respectively. Accordingly, Eb also varied. Higher austenite start and austenite finish (Af) temperatures were recorded in the anterior segments. No statistically significant differences were found for these temperatures between retrieved and new wires. The mean elemental composition was (weight percentage): Ni, 52.6 ± 0.5; Ti, 47.4 ± 0.5. Conclusions: The existence of multiple force zones was confirmed in new and retrieved Bioforce archwires. The retrieved archwires demonstrated lower forces during the initial stages of deactivation in three-point bending tests, compared with new specimens. The Af temperature of these archwires may lie higher than the regular intraoral temperature. Even at 2 mm deflections, the forces recorded from these archwires may lie beyond biologically safe limits.

Keywords: Archwire, Biomaterial science, Nitinol, Transformation temperature