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

fact that the magnitude of resistance is unknown. The
orthodontist is, then, guessing how much force is needed to
move teeth without straining anchorage. 8
The application of sliding mechanics in orthodontics
has increased since the introduction of the pre-adjusted
edgewise appliance system. 9 The process can involve the
guidance of a tooth along a continuous archwire or the
movement of the wire through crown-attachment slots. In
particular, overjet reduction and space closure have been
traditionally accepted applications of sliding mechanics.
In a first premolar extraction case, a space is created
between the canine and the second premolar. In the
presence of maximum anchorage, the canine would first be
retracted bodily with the archwire guiding its
displacement. This single-tooth movement would likely
create unwanted friction that could cause “side effects”
such as uncontrolled tipping, loss of posterior anchorage,
or deepening of the overbite. 10 Forces acting posteriorly
on the anterior portion of the archwire would then be
created to retract the incisors into the remaining spaces
while allowing the excess wire to slide through the
posterior brackets and tubes. Any friction in the buccal
segments would hinder the movement of the incisal segment
and, therefore, could delay space closure. 11
6