Effects of third-order torque on frictional force of self-ligating brackets

Takeshi Muguruma, Masahiro Iijima, William A. Brantley, Karamdeep S. Ahluwalia, Naohisa Kohda, Itaru Mizoguchi

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


Objective: To investigate the effects of third-order torque on frictional properties of self-ligating brackets (SLBs). Materials and Methods: Three SLBs (two passive and one active) and three archwires (0.016 × 0.022-inch nickel-titanium, and 0.017 × 0.025-inch and 0.019 × 0.025-inch stainless steel) were used. Static friction was measured by drawing archwires though bracket slots with four torque levels (06, 106, 206, 306), using a mechanical testing machine (n = 10). A conventional stainless-steel bracket was used for comparison. Results were subjected to Kruskal-Wallis and Mann-Whitney U-tests. Contact between the bracket and wire was studied using a scanning electron microscope. Results: In most bracket-wire combinations, increasing the torque produced a significant increase in static friction. Most SLB-wire combinations at all torques produced less friction than that from the conventional bracket. Active-type SLB-wire combinations showed higher friction than that from passive-type SLB-wire combinations in most conditions. When increasing the torque, more contact between the wall of a bracket slot and the edge of a wire was observed for all bracket types. Conclusions: Increasing torque when using SLBs causes an increase in friction, since contact between the bracket slot wall and the wire edge becomes greater; the design of brackets influences static friction.

Original languageEnglish
Pages (from-to)1054-1061
Number of pages8
JournalAngle Orthodontist
Issue number6
Publication statusPublished - 2014 Nov 1
Externally publishedYes


  • Archwire
  • Friction
  • SEM
  • Self-ligating brackets

ASJC Scopus subject areas

  • Orthodontics


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