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In orthodontics, the torque generated forces from the rectangular archwires refine the teeth position. Literature shows only linear deformation in brackets during torqueing. The objective of this study was to evaluate a new phenomenon of tie wings rotation, an angular deformation in Stainless Steel (SS) brackets with SS and Beta-Titanium (β-Ti) archwires at various angles of twist. Maxillary central incisor SS 0.457 mm × 0.635 mm and 0.558 mm × 0.711 mm brackets, SS and β-Ti archwires of 0.431 mm × 0.635 mm and 0.533 mm × 0.635 mm sizes were used. Finite element analysis was performed in various bracket-archwire assemblies for simulated torque. Palatal root torque was applied and the gingival tie wings rotation was measured at selected points, from 5° to 30° angles of twist. The tie wings rotation for 30° twist with SS 0.533 mm × 0.635 mm archwire in 0.558 mm bracket ranged from 1.32° to 2.55° and with SS 0.431 mm × 0.635 mm archwire in 0.457 mm bracket from 0.71° to 1.73°. Similarly, with β-Ti 0.533 mm × 0.635 mm archwire in 0.558 mm bracket and β-Ti 0.431 mm × 0.635 mm archwire in 0.457 mm bracket, the tie wings rotation ranged from 0.73° to 1.38° and 0.39° to 0.93° respectively. The tie wings rotation were present in all the FE models. Higher archwire size, stiffness, and angles of twist showed increased rotation. Thus, clinicians should be aware of this tie wings rotation during torqueing as an additional factor for torque loss.

In orthodontic fixed appliance therapy, the archwire torque used to refine the teeth position during the treatment imparts significant forces inside the bracket slot. The objective of this study was to measure the torque relevant bracket slot deformation in Stainless Steel (SS) brackets during various degree of archwire twist. Standard edgewise brackets 0.018-inch (in.)/0.022-in. each 20 no. and 0.016 × 0.022, 0.017 × 0.025, 0.019 × 0.025, and 0.021 × 0.025 in. archwires each 10 no. were used. A novel experimental setup consisting of loading fixture and torque key mounted on a Vision Measuring System (VMS) were used to measure the brackets slot deformation. The Top Slot and Middle Slot Deformations (TSD and MSD) of the brackets for 35° angle of twist in 0.016 × 0.022 in. archwire in 0.018-in. slot, 0.019 × 0.025 in. archwire in 0.022-in. slot and for 30° angle of twist in 0.017 × 0.025 in. archwire in 0.018-in. slot and 0.021 × 0.025 in. archwire in 0.022-in. slot were measured. Results showed that the mean TSD and MSD were higher when the archwire size, the slot size and the angle of twist were greater. In the evaluated bracket-archwire combinations, the TSD were higher than MSD and the bracket slots were elastically deformed within the clinically required 35° angle of twist in the archwire. Clinicians should be aware of this torque relevant bracket slot deformation which might be a factor for torque loss and suitably incorporate archwire angle of twist.