Finite element analysis of tie wings rotation: A new phenomenon in orthodontic bracket-archwire contact assembly during simulated torque.

Abstract

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.