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

ligature is wound. 7 The force of ligation with elastomeric
ties has been estimated to be from approximately 50 grams
to 225 grams with subsequent decay due to “relaxation” of
the elastomeric material. 34,58
Recently, an alternative type of separate ligation has
become available to the orthodontic community, which is
claimed to retain the ease of elastomeric ligation
placement and removal while reducing the resistance to
sliding. This ligature, called the Slide (Leone Orthodontic
Products, Sesto Fiorentino, Firenze, Italy), is an
injection-molded polyurethane device that hooks onto the
tie wings and is placed over the facial surface of a
conventional bracket-slot. By ligating across the slot
instead of directly over the wire, the Slide places no
normal force of ligation, and essentially converts the
bracket into a tube. An in vitro study showed that this
ligature produces significantly less sliding friction
compared to conventional ligation techniques. 59
Self-Ligation
In 1933, Boyd filed a patent for the first self-
ligating bracket, the “Boyd band bracket,” which featured a
moving bar that passively entrapped the archwire in the
bracket-slot. Since then, more than 40 self-ligating
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