<abstract xmlns="http://www.w3.org/1999/xhtml"><sec><h3>Aim</h3><p>To characterise the mechanical properties and galvanic coupling of Ni-free orthodontic brackets with stainless steel (SS) and Nickel-Titanium (NiTi) orthodontic wires.</p></sec><sec><h3>Methods</h3><p>Three Ni-free bracket types (Topic [TOP], Equilibrium [EQU] and Orthos [ORT] made of Ni-free alloys), one conventional (Mini 2000 [MIN]) made of SS alloy and an SS and a NiTi wire were examined in the present study. All brackets and wires were embedded in epoxy resin and, after metallographic grinding and polishing, the Martens hardness (HM), the indentation modulus (E<sub>IT</sub>), and the elastic index (η<sub>IT</sub>) were recorded, employing Instrumented Indentation Testing (IIT) by monitoring force over indentation depth curves during a loading-unloading cycle. The galvanic coupling of all bracket-wire combinations was tested in 0.1M NaCl-0.1M lactic acid and 0.3% (wt.) NaF solutions by noting the potential differences over 48 hours. The mechanical properties were statistically analysed by one-way ANOVA and Tukey multiple comparison tests at alpha = 0.05.</p></sec><sec><h3>Results</h3><p>Significant differences were identified in the mechanical properties of the materials tested. The TOP (2372 ± 182 N/ mm<sup>2</sup>), ORT (wing) (2418 ± 164) and SS wire (2302 ± 85) showed significantly higher HM compared with all other materials tested. The MIN (base) (1115 ± 81) and ORT (base) (1237 ± 101) showed the lowest HM while MIN (wing) (1520 ± 138), EQU (1620 ± 139) and NiTi wire (1526 ± 42) demonstrated intermediate HM values. The ORT (wing) (101 ± 6 GPa) displayed the highest E<sub>IT</sub> while NiTi wire (24 ± 5) showed the lowest. The latter had the highest elastic index (59 ± 5%) with MIN (base)(15 ± 3) possessing the lowest. The potential difference for all bracket wire combinations was found below the threshold for the initiation of galvanic corrosion (200 mV) apart from MIN coupled with NiTi wire in the NaF solution.</p></sec><sec><h3>Conclusions</h3><p>The mechanical properties of Ni-free brackets are significantly different compared with the SS bracket assessed. Galvanic testing revealed that conventional and Ni-free brackets are compatible with both SS and NiTi wires in media containing chloride and fluoride ions.</p></sec></abstract>

AimTo characterise the mechanical properties and galvanic coupling of Ni-free orthodontic brackets with stainless steel (SS) and Nickel-Titanium (NiTi) orthodontic wires.MethodsThree Ni-free bracket types (Topic [TOP], Equilibrium [EQU] and Orthos [ORT] made of Ni-free alloys), one conventional (Mini 2000 [MIN]) made of SS alloy and an SS and a NiTi wire were examined in the present study. All brackets and wires were embedded in epoxy resin and, after metallographic grinding and polishing, the Martens hardness (HM), the indentation modulus (EIT), and the elastic index (ηIT) were recorded, employing Instrumented Indentation Testing (IIT) by monitoring force over indentation depth curves during a loading-unloading cycle. The galvanic coupling of all bracket-wire combinations was tested in 0.1M NaCl-0.1M lactic acid and 0.3% (wt.) NaF solutions by noting the potential differences over 48 hours. The mechanical properties were statistically analysed by one-way ANOVA and Tukey multiple comparison tests at alpha = 0.05.ResultsSignificant differences were identified in the mechanical properties of the materials tested. The TOP (2372 ± 182 N/ mm2), ORT (wing) (2418 ± 164) and SS wire (2302 ± 85) showed significantly higher HM compared with all other materials tested. The MIN (base) (1115 ± 81) and ORT (base) (1237 ± 101) showed the lowest HM while MIN (wing) (1520 ± 138), EQU (1620 ± 139) and NiTi wire (1526 ± 42) demonstrated intermediate HM values. The ORT (wing) (101 ± 6 GPa) displayed the highest EIT while NiTi wire (24 ± 5) showed the lowest. The latter had the highest elastic index (59 ± 5%) with MIN (base)(15 ± 3) possessing the lowest. The potential difference for all bracket wire combinations was found below the threshold for the initiation of galvanic corrosion (200 mV) apart from MIN coupled with NiTi wire in the NaF solution.ConclusionsThe mechanical properties of Ni-free brackets are significantly different compared with the SS bracket assessed. Galvanic testing revealed that conventional and Ni-free brackets are compatible with both SS and NiTi wires in media containing chloride and fluoride ions.

Galvanic coupling and mechanical properties of low Ni orthodontic brackets with representative types of orthodontic wires

National and Kapodistrian University of Athens

Australasian Orthodontic Journal

This work is licensed under the Creative Commons Attribution 4.0 International License.

AimTo characterise the mechanical properties and galvanic coupling of Ni-free orthodontic brackets with stainless steel (SS) and Nickel-Titanium (NiTi)...

Galvanic coupling and mechanical properties of low Ni orthodontic brackets with representative types of orthodontic wires

Published Online: Jul 20, 2021

Page range: 53 - 60

Received: Oct 01, 2018

Accepted: Mar 01, 2019

DOI: https://doi.org/10.21307/aoj-2020-033

© 2019 Géraldine Kummer et al., published by Sciendo

This work is licensed under the Creative Commons Attribution 4.0 International License.