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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 November 22, 2022

Copyright © The Korean Association of Orthodontists.

Transformation temperatures and mechanical properties in bending of a multizone NiTi archwire: a retrieval analysis study.

Panagiotis Roulias1, Ioulia-Maria Mylonopoulou2, Iosif Sifakakis3, Christoph Bourauel4, Theodore Eliades5

1 Postgraduate Student, Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Greece
2 Research Associate, Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Greece
3Assistant Professor, Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Greece
4 Professor, Department of Oral Technology, School of Dentistry, University Hospital Bonn, Germany
5 Professor, Clinic of Orthodontics and Paediatric Dentistry, Center of Dental Medicine, University of Zurich, Switzerland

Correspondence to:Iosif Sifakakis,
2 Thibon str, 11527 Goudi, Athens, Greece,
isifak@dent.uoa.gr
Tel.: 00302107461228

Abstract

Objective:
The aim of this study was to compare the mechanical and thermal properties in the anterior and posterior segments of new and retrieved specimens of a common multizone superelastic NiTi archwire.
Methods:
The following groups of 0.016x0.022-inch Bioforce NiTi archwires were compared: a) new specimens, in the anterior and b) posterior region, as well as c) retrieved specimens in the anterior and d) posterior region.
6 specimens were evaluated in each group, by 3-point bending and bend and free recovery tests. Bending moduli (Eb) were also calculated. Additionally, the new specimens were evaluated with SEM/EDS analysis. A multiple linear regression model with a random intercept at the wire level was applied for data analysis.
Results:
The forces of the posterior segments or new specimens were higher than these recorded in the anterior segments or retrieved specimens respectively. Eb varied accordingly.
Higher As (austenite start) and Af (austenite finish) 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 (percent weight): Ni= 52.6±0.5 and 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 force levels during the initial stages of deactivation in 3-point bending tests, in comparison with new specimens. The Af temperature of these archwires may lie higher than the usual mouth temperature.
Even at 2 mm deflections, the forces recorded from these archwires may lie beyond biologically safe limits.

Keywords: wire, biomaterial science, nitinol, transformation temperature

Article

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Korean J Orthod   

First Published Date November 22, 2022

Copyright © The Korean Association of Orthodontists.

Transformation temperatures and mechanical properties in bending of a multizone NiTi archwire: a retrieval analysis study.

Panagiotis Roulias1, Ioulia-Maria Mylonopoulou2, Iosif Sifakakis3, Christoph Bourauel4, Theodore Eliades5

1 Postgraduate Student, Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Greece
2 Research Associate, Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Greece
3Assistant Professor, Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Greece
4 Professor, Department of Oral Technology, School of Dentistry, University Hospital Bonn, Germany
5 Professor, Clinic of Orthodontics and Paediatric Dentistry, Center of Dental Medicine, University of Zurich, Switzerland

Correspondence to:Iosif Sifakakis,
2 Thibon str, 11527 Goudi, Athens, Greece,
isifak@dent.uoa.gr
Tel.: 00302107461228

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:
The aim of this study was to compare the mechanical and thermal properties in the anterior and posterior segments of new and retrieved specimens of a common multizone superelastic NiTi archwire.
Methods:
The following groups of 0.016x0.022-inch Bioforce NiTi archwires were compared: a) new specimens, in the anterior and b) posterior region, as well as c) retrieved specimens in the anterior and d) posterior region.
6 specimens were evaluated in each group, by 3-point bending and bend and free recovery tests. Bending moduli (Eb) were also calculated. Additionally, the new specimens were evaluated with SEM/EDS analysis. A multiple linear regression model with a random intercept at the wire level was applied for data analysis.
Results:
The forces of the posterior segments or new specimens were higher than these recorded in the anterior segments or retrieved specimens respectively. Eb varied accordingly.
Higher As (austenite start) and Af (austenite finish) 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 (percent weight): Ni= 52.6±0.5 and 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 force levels during the initial stages of deactivation in 3-point bending tests, in comparison with new specimens. The Af temperature of these archwires may lie higher than the usual mouth temperature.
Even at 2 mm deflections, the forces recorded from these archwires may lie beyond biologically safe limits.

Keywords: wire, biomaterial science, nitinol, transformation temperature