Evaluation of force released by deflection of orthodontic wires in conventional and self-ligating brackets

INTRODUCTION: The aim of the study was to evaluate deflection forces of rectangular orthodontic wires in conventional (Morelli(TM)), active (In-Ovation R(TM)) and passive (Damon 3MX(TM)) self-ligating brackets. MATERIAL AND METHODS: Two brands of stainless steel and nickel-titanium (NiTi) wires (Morelli(TM) and GAC(TM)), in addition to Ormco(TM) copper-nickel-titanium wires were used. Specimens were assembled in a clinical simulation device especially designed for this study and tested in an Instron universal testing machine. For the testing procedures, an acrylic structure representative of the maxillary right central incisor was lingually moved in activations of 0 to 1 mm, with readings of the force released by deflection in unloading of 0.5, 0.8 and 1 mm at a constant speed of 2 mm/min. Inter-bracket forces with stainless steel, NiTi and CuNiTi were individually compared by two-way ANOVA, followed by Tukey’s tests. RESULTS: Results showed that there were lower forces in conventional brackets, followed by active and passive self-ligating brackets. Within the brands, only for NiTi wires, the Morelli(TM) brand presented higher forces than GAC(TM) wires. CONCLUSIONS: Bracket systems provide different degrees of deflection force, with self-ligating brackets showing the highest forces.