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

designs. The passive-slide design of the Damon series of
brackets utilizes a sliding “door” that closes the slot,
effectively transforming the bracket into a tube. The
SmartClip bracket features a nickel-titanium alloy “C-clip”
lateral to each of the mesial and distal tie-wings 76 ; an
archwire that is snapped into the bracket-slot may remain
passive in the lumens of the clips. The claimed benefit of
passive self-ligation is reduced friction with a variety of
wire sizes, resulting in faster tooth movement. 77 With the
lack of a lingually directed force on the archwire,
however, some critics argue that controlling torque could
be a problem. 58 In addition, Harradine 63 points out that, in
theory, a passively ligated bracket with an engaged
rectangular wire, having a faciolingual dimension of 0.025
inches, could bring a facially displaced tooth only to
within 0.002 inches of the adjacent teeth because of its
slot depth; usually it is approximately 0.027 inches. An
active clip would, theoretically, not have this problem
because it “squeezes” in the slot an archwire as small as
0.018 inches in the faciolingual dimension. Harradine 63
stated, however, that a remaining, clinically significant
malalignment was unlikely. In two investigations, no
significant difference between either the SmartClip bracket
or the Damon 2 bracket and a conventional bracket in regard
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