Mechanical evaluation of space closure loops in Orthodontics

Abstract

This study evaluated the mechanical performance of teardropshaped loops and teardrop-shaped loops with helix used in orthodontic space closure. Sixty retraction loops made with 0.019" x 0.025" stainless steel (SS) and beta-titanium (BT) wires were used. They were attached to a testing machine to measure the magnitudes of the sagittal force and the load-deflection ratio necessary for 1 mm, 2 mm and 3 mm activation. The results demonstrated that the BT alloy presented significantly smaller mean values (p < 0.01) of sagittal force and load-deflection than the SS alloy. The loop with the highest mean value of sagittal force and load-deflection was the teardrop-shaped loop (p < 0.01). Differences were observed in the mean values of sagittal force and load-deflection among activations, and the highest mean value was found in the activation of 3 mm, while the smallest mean value was evident in the activation of 1 mm (p < 0.01). It could be concluded that the metallic alloy used and the presence of a helix in configuration of the loops may have a strong influence on the sagittal force produced and on the load-deflection ratio; the teardrop-shaped loops and teardrop-shaped loops with helix in BT presented the release of lighter forces; the teardrop-shaped loop in SS generated a high load-deflection ratio, providing high magnitudes of horizontal force during its deactivation.

Evaluation of Biomechanical Properties of Four Loops at Different Activation: A Finite Element Method Study

“…For a given cross section, TMA can be deflected approximately twice as far as SS without permanent deformation, which delivers force values less than half that of SS. 8 The present study is in accordance with the study conducted by Rodrigues et al 13 They compared the properties of Teardrop loop with beta titanium and SS and concluded that the beta titanium loops produce lower amount of horizontal force and F/D ratio than the SS loops. According to the study conducted by Vibhute et al, 14 Teardrop loop with a preactivation bend of 34° provided 82 to 303 g of force and 1.7 to 7.3:1 proportion of M/F ratio from its neutral position to +2 mm activation.…”

Comparative Evaluation of the Force and Load Deflection Rate for Different Loop Springs with Varying Designs, Wire Dimensions, and Materials: A Finite Element Method Study

“…This is similar to the findings of Faulkner, Lipsett, El-Rayes, and Haberstock 2 and Rodrigues, Maruo, Guariza, Tanaka, and Camargo. 6 The force increased in a linear fashion with each millimeter of activation. This was indicative of the fact that the maximum displacement was under the elastic limit for all the loops.…”

“…Beta titanium is less stiff than stainless steel which has been demonstrated by numerous studies. 6,[9][10][11][12][13] The 0.019" × 0.025" wire dimensions produced more force and load deflection rate than 0.017" × 0.025" (Tables 3 and 4, Graph 1). The 0.019" × 0.025" produced approximately 1.4 times more force than 0.017" × 0.025" wire dimensions.…”

In vitro evaluation of loop design influencing the sliding of orthodontic wires: A preliminary study

“…By comparing loops of the same height, significant differences were found between open and closed loops regarding F SS and F DS , for both 0.016″×0.022″ and 0.017″×0.025″ wires, confirming the relevance of open loops to reduce the RS. Greater RS with closed loops may be explained by the helix, which has been associated to reduced load-deflection ratio, 19 and greater wire deflections leading to earlier binding. 5 Not surprisingly, RS values were different between 0.016″×0.022″ and 0.017″×0.025″ wires, with larger wires increasing the F SS up to 43.3% and the F DS up to 49.5% compared to smaller ones.…”

“…Perhaps surprisingly, even though it is common to use loops to control the mechanical properties of wires, 19 to the best of our knowledge no published studies have investigated how to control the RS through the use of loops.…”