Mechanical Characteristics of the Bull Loop Modified During the Orthodontic Space Closure

Roberto Hideo SHIMIZU, Tatsuko SAKIMA, Ary dos SANTOS-PINTO, Dirceu SPINELLI, Isabela Almeida SHIMIZU

The purpose of this study was to evaluate the Bull loop’s force system when it was in the middle of the interbracket space, and constructed with different stainless steel wire thickness, activation and preactivation. Eighty Bull loops, made with stainless steel wire 18/8 UNITEK, were evaluated through mechanics tests, for four different thickness: .017”x .025”, .018”x .025”, .019”x .025”, .021”x.025”; and four different preactivation: 0º, 20º, 30º and 40º. According to the results, it could be concluded that the preactivation increased the force magnitude of Bull loop; the Bull loop showed lower M/F proportion, presenting only the uncontrolled inclination movement.

Keywords: Orthodontic. Tooth Extration. Orthodontic Space Closure. Traction Resistance. Orthodontics Loops.

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