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

self-ligating bracket systems to mainstream orthodontics.
These newer brackets are claimed to reduce friction,
contribute to improved oral hygiene, lessen anchorage loss,
and shorten chair- time as well as treatment-time. 38,62-65
Several studies have reported that self-ligating brackets
generate less sliding friction than elastomerically tied
brackets. 5,38,40,42-46
In general, self-ligating brackets fall into one of
two categories based on the design of the slot-closure. An
“active” design features a resilient spring-clip that snaps
closed and reduces the faciolingual slot depth to
approximately 0.018 inches. Because this clip can store
energy when it is activated by a lingual malalignment, a
rotated tooth or a twisted rectangular wire, it has the
potential to exert lingual force on the wire and help bring
the tooth into its proper position. 66 Critics of the clip-
design say, however, that introducing an active component
into the ligation unnecessarily increases frictional
resistance. 67 Some investigators have found that any
advantage from decreased friction with active self-ligating
brackets is reduced when rectangular wires are
placed. 5,43,63,68-71 It has also been suggested that the
asymmetric design of the cantilevered clip delivers a
diagonally directed force to the archwire, in effect
53