The effects of third-order torque and self - Saint Louis University

otated tooth or a twisted rectangular wire, it has the
potential to deliver lingual force to the wire and help
bring the tooth into its proper position. 60 The Speed
bracket, the In-Ovation R bracket and the Time2 bracket
(American Orthodontics, Sheboygan, WI) all feature active
clips within their designs. It is suggested by product
literature that active ligation helps deliver full torque
expression when a rectangular wire is engaged and pressed
against the base of the slot. Critics of the clip design
say, however, that introducing an active component into the
ligation unnecessarily increases frictional resistance.
Some investigators have found that any advantage from
decreased friction with active self-ligating brackets is
reduced when rectangular wires are placed. 9,48,65,71-74 Other
researchers have found the same to be true for the passive
Damon SL II. 75 It has also been suggested that the
cantilevered clip delivers a diagonally directed force to
the archwire, in effect reducing the torquing efficiency
and causing errors in torque expression. 63
In contrast, “passive” ligating mechanisms, like those
of the Damon 2, Damon 3 and Damon 3MX brackets and the
SmartClip bracket (3M/Unitek Corporation, Monrovia, CA), do
not invade the slot and place no inherent normal force on
the archwire. These systems feature one of two basic
25