Superelasticity and force plateau of nickel-titanium springs: an in vitro study

Vieira, Camila Ivini Viana; Caldas, Sergei Godeiro Fernandes Rabelo; Martins, Renato Parsekian

doi:10.1590/2177-6709.21.3.046-055.oar

Cited by 11 publications

(14 citation statements)

References 21 publications

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“…diminish [4,6,17,18] (Fig. 9) as occurred in this investigation, where overactivation of the loops produced lower forces.…”

Section: Discussionsupporting

confidence: 65%

“…1). This characteristic suggests that overactivated nickel-titanium loops might improve the performance of orthodontic appliances as previously suggested [5,6]. Even though there have been other reports on nickel-titanium T-loops [3,7e9], no study has yet investigated the effects of overactivation to eliminate the sudden drop of force at the beginning of the reverse transformation.…”

Section: Introductionmentioning

confidence: 63%

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Effects of height and overactivation on a composite nickel-titanium T-loop

Ribeiro¹,

Martins

Silva

et al. 2017

Journal of the World Federation of Orthodontists

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Objective: Evaluate the effect of height and overactivation on the force system produced by composite nickel-titanium T-loops. Material and Methods: Forty nickel-titanium/stainless steel (SS) T-loops were divided into four groups according to height (7 or 6 mm) and activation/deactivation protocol (7 mm or 7 mm with 2 mm of overactivation). An Orthodontic Force Tester recorded the y-axis force and the x-axis moment produced for each 0.5 mm of deactivation, while the moment(x)-to-force(y) (M/F) ratio was calculated. The data were analyzed by three analyses of variance of repeated measures to detect differences and interactions between height and protocol on the three variables. Results: T-loops with a height of 6 mm produced higher forces (2.97 N vs. 2.66 N) than those of 7 mm. The moments were similar, whereas the M/F was larger for the 7-mm loops (5.76 mm vs. 4.92 mm). The conventional activation produced higher forces (2.99 N vs. 2.64 N), higher moments (16.2 Nmm vs. 13.59 Nmm) but the same M/F. The M/F showed an interaction with deactivation. Conclusion: The 6-mm-high T-loops produced higher forces, but lower M/F. The conventional protocol produced higher forces and moments. The M/F ratio was similar for both protocols, but overactivation produced a nearly constant M/F throughout deactivation. The use of a 7-mm-high overactivated segmented nickel-titanium loop might improve the performance of orthodontic space closure.

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“…diminish [4,6,17,18] (Fig. 9) as occurred in this investigation, where overactivation of the loops produced lower forces.…”

Section: Discussionsupporting

confidence: 65%

Section: Introductionmentioning

confidence: 63%

Effects of height and overactivation on a composite nickel-titanium T-loop

Ribeiro¹,

Martins

Silva

et al. 2017

Journal of the World Federation of Orthodontists

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“…For that reason, limiting nickel-titanium springs activation with the purpose of maintaining forces at a low level is illogical. Moreover, it appears to be a good idea to overactivate those springs upon affixation, in order to improve the springs ability to produce constant and relatively lower forces 17 . That directly connects to the fact that the vast majority of nickel-titanium materials does not behave in a superelastic manner when used in Orthodontics, due to the fact that they are not activated enough to produce SIMT.…”

Section: Discussionmentioning

confidence: 99%

Deformation of nickel-titanium closed coil springs: an in vitro study

Vieira

Reis

Vaz

et al. 2017

Dental Press J. Orthod.

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Objective: The aim of this paper was to determine the amount of deformation in four commercial brands of nickel-titanium closed springs. Methods: A total of 130 springs were divided into 13 subgroups, according to their features and manufacturers (Morelli, Orthometric, Ormco and GAC) and activated from 100% to 1000% of the effective length of the nickel-titanium portion present at the spring, at 37 °C. Deactivation data were plotted and deformation was found graphically. The values were compared by analysis of variance and Tukey's post-hoc test.Results: Springs manufactured by Morelli had the same amount of deformation when they were activated up to 700% of Y activation; springs by Orthometric had the same amount of deformation up to 600-700% of Y; springs by Ormco had the same amount of deformation up to 700-800% of Y; and finally, the majority of springs by GAC had similar deformation up to 800%-1000% of activation. All springs tested could be activated up to 700% without rupture.Conclusions:Most subgroups were similarly deformed up to 700% of activation, without rupture of springs. Subgroups 4B, 4C, 4D and 4E showed the same amount of deformation up to 1000% of activation without any rupture at all.

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“…These differences are probably due to the height of the T-loops of these reports (8.45 mm 10,12 ), which were larger than ours. A peculiar characteristic of shape memory alloys upon reverse transformation from stress-induced martensite is a drop of load before a pseudoelastic plateau is described on a load-deflection graph, 7,20,21 and this effect can be perceived on the forces measured of the T-loops (Table 7; Figure 5). As it has already been suggested for NiTi close coil springs, 22 it may be a good idea to overactivate NiTi T-loops if a more constant force is desired.…”

Section: Discussionmentioning

confidence: 99%

“…23 That large stress concentration induces a stress-induced martensitic transformation that will make that region more flexible rather than more rigid; moreover, further increasing the angulation in that region will cause a different effect than the desired one because higher stresses will make the load/deflection rate of NiTi even lower. 7,21 A solution for that problem has been shown by Bourauel and colleagues 9 with parallel tubes and stainless steel base wires, but that would still allow stress relaxation to occur in that specific region, because there was a 90u bend in the stainless steel base wire after the tubes. We have found a different solution, which was the addition of a crimpable cross tube in that particular area, making it more rigid and adding stainless steel base wires, preactivated by curvature, rather than NiTi base wires, which would probably not produce enough moments.…”

Section: Niti T-loop Wire Dimensions For En Masse Retractionmentioning

confidence: 99%

Nickel titanium T-loop wire dimensions for en masse retraction

Almeida

Ribeiro²,

Martins

et al. 2016

The Angle Orthodontist

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Objective: To compare the force system produced by nickel-titanium T-loop springs made with wires of different dimensions. Material and Methods: Thirty compound T-loop springs were divided into three groups according to the dimensions of the nickel-titanium wire used for its design: 0.016" 3 0.022", 0.017" 3 0.025", and 0.018" 3 0.025". The loops were tested on the Orthodontic Force Tester machine at an interbracket distance of 23 mm and activated 9 mm. The force in the y-axis and the moment in the x-axis were registered while the calculated moment to force ratio was recorded at each .5 mm of deactivation. The data were analyzed by three analyses of variance of repeated measures to detect differences and interactions between deactivation and wire size on force, moment, and moment-force ratios (M/F). Results: All groups had significantly different forces (P , .001). The 0.016" 3 0.022" wire produced 1.78N of force while the 0.017" 3 0.025" and the 0.018" 3 0.025" produced 2.81 N and 3.25 N, respectively. The 0.016" 3 0.022" wire produced lower moments (11.6 Nmm) than the 0.017" 3 0.025" and 0.018" 3 0.025" wires, which produced similar moments (13.9 Nmm and 14.4Nmm, respectively). The M/F produced was different for all groups; 0.016" 3 0.022" T-loops produced 6.7 mm while the 0.017" 3 0.025" and 0.018" 3 0.025" T-loops produced 5.0 mm and 4.5 mm, respectively. An interaction was detected for all variables between deactivation and groups.Conclusion: The larger wires tested produced higher forces with slight increase on the moments, but the M/F produced by the 0.016" 3 0.022" wire was the highest found. (Angle Orthod. 2016;86:810-817.)

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Superelasticity and force plateau of nickel-titanium springs: an in vitro study

Cited by 11 publications

References 21 publications

Effects of height and overactivation on a composite nickel-titanium T-loop

Effects of height and overactivation on a composite nickel-titanium T-loop

Deformation of nickel-titanium closed coil springs: an in vitro study

Nickel titanium T-loop wire dimensions for en masse retraction

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