Comparison of torque expression among passive self-ligating brackets with different slot depths: An in vitro study

Introduction > The aim of this study was to assess the interaction between a 0.019 x 0.025-inch ('') stainless steel archwire and two types of passive self-ligating brackets with the same slot height (0.022 '') and different slot depths (0.028 '' and 0.026 '', and to measure the archwire/slot play as well as to compare the torque expression with archwire torsions of 12 degrees, 24 degrees, and 36 degrees. Material and methods > An experimental device was developed along with a universal testing machine to measure torque expression in two types of brackets with 0.028 '' and 0.026 '' slot depths. Analysis of variance (ANOVA) and Tukey's test were performed to identify the differences between groups. Results > The 0.026 '' slot bracket presented greater archwire/slot play when compared to the 0.028 '' bracket. Torque expression with torsions of 24 degrees and 36 degrees were significantly higher in the 0.028 '' depth brackets when compared to the 0.026 '' depth brackets. Conclusion > The 0.022 '' x 0.026 '' passive self-ligating brackets attached with a 0.019 '' x 0.025 '' stainless steel archwire provided no greater torque control when compared to 0.022 '' x 0.028 '' passive self-ligating brackets.