An Observational 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.


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.

  • The study involved the use of a custom-designed typodont system composed of resin teeth and a metal frame that could be moved up, down, forward and backward to produce malocclusions while stimulating the 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.
  • There were significant differences in frictional force depending on the 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 dimension when closed, creating friction when the archwire comes into contact with the slot.
  • Damon displayed lower frictional force than all other brackets.
  • Passive slide designs such as Damon "might be the most effective with respect to friction."