Determination of the force systems produced by different configurations of tear drop orthodontic loops

Guilherme Thiesen,Jefferson Ricardo Pereira,Karyna Martins Do Valle-Corotti,Caio Vinicius Martins Do Valle,Paulo Cesar Rodrigues Conti,Roberto Hideo Shimizu

doi:10.1590/s2176-94512013000200007

Abstract

To determine the mechanical characteristics of teardrop loop with and without helix fabricated using different metal alloy compositions (stainless steel and beta-titanium), submitted to different intensities of bends preactivation (0° and 40°), and with different cross-sectional dimension of the wire used to build these loops (0.017 x 0.025-in and 0.019 x 0.025-in). Eighty loops used to close spaces were submitted to mechanical tests. The magnitudes of horizontal force, the moment/force ratio, and the load/deflection ratio produced by the specimens were quantified. Loops were submitted to a total activation of 5.0 mm and the values were registered for each 1.0 mm of activation. For statistic data analysis, a analysis of variance was performed and a Tukey's Multiple Comparison test was used as supplement, considering a 5% level of significance. In general, teardrop loops with helix produced lower magnitudes of horizontal force and load/deflection ratio, and higher moment/force ratio than teardrop loops without helix. Among all analyzed variables, metal alloy composition presented greater influence in the horizontal force and in the load/deflection ratio. The moment/force ratio showed to be more influenced by the preactivation of loops for space closure.

Highlights

Space closure in orthodontics, those from tooth extractions, still represents a challenge to the professional in this area
It was possible to observe that, in general way, the horizontal force liberated by teardrop loops suffered greater influence from metal alloy composition, and the stainless steel alloy presented greater magnitude of force than beta-titanium alloy
It was possible to observe that, in general, the horizontal force liberated by teardrop loops with helix suffered greater influence of metal alloy composition, and the stainless steel presented higher magnitudes of force than beta-titanium alloy

Summary

Introduction

Those from tooth extractions, still represents a challenge to the professional in this area. It occurs mainly due to the increase in treatment time, patient discomfort, as well as the pursuit of excellence on the finishing stage. These factors are related to the method used to achieve such result. During the development of orthodontics specialty, several devices have been elaborated to close these spaces Such mechanisms present a wide variety of designs, thicknesses and wire configurations, source of force application, and factors related to anchorage control.[4] Among several devices described in the literature, there are a wide range of loops which once incorporated to continuous or segmented arches can be used for tooth movement. Current knowledge in biomechanics, allied to the development of new materials, made possible a great upgrading in space closure loops configuration, which has simplified the mechanics and improved tissue answers, minimizing the biological cost of treatment.[2,3,6,21,24]

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Conclusion