Investigation into the effects of stainless steel ligature ties on the mechanical characteristics of conventional and self-ligated brackets subjected to torque.

OBJECTIVE: Torque is applied to orthodontic brackets in order to alter the buccal-lingual angulation of a tooth. One factor that can affect torque is the ligation mode used to retain the archwire in the bracket slot. The objective of this study was to investigate the effects of stainless steel ligation on torque expression and bracket deformation. METHODS: This study utilized 60 upper right central incisor Damon Q brackets and 60 Ormco Orthos Twin brackets. The brackets used in this study were subdivided into four groups: (1) Damon Q ligated with SS ligature; (2) Damon Q with the sliding bracket door; (3) Orthos Twin bracket ligated with SS wire; and (4) Orthos Twin ligated with elastic ties. All brackets were tested using an orthodontic torque simulating device that applied archwire rotation from 0° to 45°. RESULTS: All brackets ligated with stainless steel ties exhibited greater torque expression and less deformation than brackets without stainless steel ties. As well, Damon Q brackets exhibit less bracket deformation than Orthos Twin brackets. CONCLUSIONS: Stainless steel ties can reduce the amount of plastic deformation for both types of brackets used in this study.