title: Mechanical evaluation of space closure loops in orthodontics.
abstract: This study evaluated the mechanical performance of teardrop-shaped 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.
authors.affiliation: Department of Orthodontics, Pontifical Catholic University of Paraná, Curitiba, Paraná, Brazil.
authors.forename: Eduardo Uggeri
authors.initials: EU
authors.lastname: Rodrigues
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Maruo
authors.forename: Odilon
authors.initials: O
authors.lastname: Guariza Filho
authors.forename: Orlando
authors.initials: O
authors.lastname: Tanaka
authors.forename: Elisa Souza
authors.initials: ES
authors.lastname: Camargo
mesh_terms: D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D008422:Materials Testing; D016382:Orthodontic Appliance Design; D019516:Orthodontic Space Closure; D009969:Orthodontic Wires; D013193:Stainless Steel; D018709:Statistics, Nonparametric; D014025:Titanium
chemical_list: C023988:beta titanium; D013193:Stainless Steel; D014025:Titanium