Active and passive self-ligation: a myth? Part 1: torque control

Angle Orthod. 2012 Jul;82(4):663-9. doi: 10.2319/062011-673.1. Epub 2011 Nov 7.


Objective: To determine the amount of torque expressed by various self-ligating brackets and to evaluate the influence of active clip designs.

Materials and methods: Torque moments were measured for nine different bracket types in combination with a 0.019 × 0.025 inch stainless-steel archwire. All active brackets were measured in an open and a closed configuration to evaluate the influence of the self-ligating spring clip. In addition, slot dimensions were optically measured and compared to the torque expression.

Results: Moments between 3.1 Nmm and 22.6 Nmm were observed at an angulation of 30° between archwire and slot. The amount of torque contributed by the spring clip of active self-ligating brackets was approximately 1 Nmm; 10 Nmm of torque was achieved with most brackets with a 20°-25° angulation between archwire and slot. The slot dimensions ranged from 0.0222 inch (0.563 mm) to 0.0241 inch (0.613 mm).

Conclusion: The influence of the ligature or the active or passive self-ligating mechanism is minimal, and slot dimensions are far more important for the transmission of torque. The amount of torque exerted by the active spring clip is approximately 1/10th of the torquing moments recommended in the literature.

Publication types

  • Comparative Study

MeSH terms

  • Analysis of Variance
  • Dental Stress Analysis*
  • Friction
  • Humans
  • Orthodontic Appliance Design / methods*
  • Orthodontic Brackets*
  • Orthodontic Wires*
  • Stainless Steel
  • Torque


  • Stainless Steel