Comparison of frictional forces during the initial leveling stage in various combinations of self-ligating brackets and archwires with a custom-designed typodont system.

INTRODUCTION The purpose of this study was to compare the frictional force (FF) generated by various combinations of self-ligating bracket (SLB) types, archwire sizes, and alloy types, and the amount of displacement during the initial leveling phase of orthodontic treatment, by using a custom-designed typodont system. METHODS Two passive SLBs (Damon 2 [D2] and Damon 3 [D3]), and 3 active SLBs (SPEED [SP], In-Ovation R [IO], Time 2 [T2]), and SmartClip (SM) were tested with 0.014-in and 0.016-in austenitic nickel-titanium (A-Ni-Ti) and copper-nickel-titanium (Cu-Ni-Ti) archwires. To simulate malocclusion status, the maxillary canines (MXCs) were displaced vertically, and the mandibular lateral incisors (MNLIs) horizontally from their ideal positions up to 3 mm with 1-mm intervals. Static and kinetic FFs were measured with a speed of 0.5 mm per minutes for 5 minutes with a testing machine (model 4466, Instron, Canton, Mass). Two conventional brackets (Mini-Diamond [MD] and Clarity [CL]) were used as controls. Analysis of variance and Duncan tests were used for statistical purposes. RESULTS FF was increased in ascending order: D2, D3, IO, T2, SM, SP, CL, and MD in the maxillary typodont; and IO, D2, D3, T2, SP, CL, and MD in the mandibular typodont, regardless of archwire size and alloy type. The A-Ni-Ti wire showed significantly lower FF than did the Cu-Ni-Ti wire of the same size. As the amounts of vertical displacement of the MXCs and horizontal displacement of the MNLIs were increased, FF also increased. CONCLUSIONS These findings suggest that combinations of the passive SLB and A-Ni-Ti archwire during the initial leveling stage can produce lower FF than other combinations of SLB and archwire in vitro.