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

Kim TK, Kim KD, Baek SH. American Journal of Orthodontics & Dentofacial Orthopedics 2008; 187:e15-e24.

Objective

To compare the frictional force generated by different self-ligating brackets, archwires and alloy types, and to measure the amount of displacement during the initial leveling phase of orthodontic treatment.

Methodology

  • Study involved use of a custom-designed typodont system composed of resin teeth and metal frame that could be moved up, down, forward and backward to produce malocclusions while stimulating initial leveling phase and measuring levels of frictional force.
  • The following brackets were tested: Damon 2, Damon 3, In-Ovation R, Speed, Time 2, SmartClip, Clarity and Mini-Diamond. Data involving SmartClip was discarded, because the SmartClip bracket could not grip the archwire firmly during the test.
  • For initial leveling and alignment, .014 and .016 austenitic nickel-titanium and copper-nickel titanium archwires were tested with each bracket.

Results

  • There were significant differences in frictional force depending on bracket, wire alloy and size, and the amount of displacement in the maxillary and mandibular typodonts.
  • In the maxillary typodont, Damon 2 and Damon 3 brackets produced "significantly" lower frictional force than all other brackets even though the degree of malocclusion was increased.
  • In the mandibular typodont, Damon and In-Ovation brackets produced lower frictional force. However, the authors note that when an archwire contacts the clip or slides of an active bracket like In-Ovation, frictional force increases and can result in little or no tooth movement.
  • The slide of the Damon passive self-ligating brackets does not change the lumen size of the bracket slot when closed. In contrast, the clip of active self-ligating brackets can reduce slot depth and the dimension when closed, creating friction when the archwire comes into contact with the slot.

Conclusion

  • Damon displayed lower frictional force than all other brackets.
  • Passive slide designs such as Damon "might be the most effective with respect to friction."