The effects of third-order torque and self - Saint Louis University
The effects of third-order torque and self - Saint Louis University
The effects of third-order torque and self - Saint Louis University
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surfaces. 6 <strong>The</strong> magnitudes <strong>of</strong> the coefficients <strong>of</strong> friction<br />
are generally between zero <strong>and</strong> one. 5<br />
Friction in Orthodontics<br />
Because frictional force acts in a direction opposite<br />
to the intended path <strong>of</strong> the object to be displaced, <strong>and</strong><br />
sliding mechanics are commonplace in orthodontic therapy,<br />
an underst<strong>and</strong>ing <strong>of</strong> friction is necessary to achieve<br />
optimal clinical results. Fixed-appliance therapy usually<br />
involves some relative wire-slot displacement in various<br />
phases <strong>of</strong> treatment; hence, the generation <strong>of</strong> friction<br />
during tooth movement can be problematic for the<br />
orthodontist. Because a portion <strong>of</strong> the force for delivery<br />
to a tooth-crown may be necessary to overcome frictional<br />
resistance, the orthodontist must be sure to use a force <strong>of</strong><br />
sufficient magnitude to also initiate a biological response<br />
in the supporting tissues. 7 Frictional resistance is<br />
thought play a role in delayed tooth movement, undesired<br />
movement <strong>and</strong> loss <strong>of</strong> anchorage. 6 Examination <strong>of</strong> its effect<br />
on orthodontic anchorage, however, reveals that, in some<br />
situations, the presence <strong>of</strong> friction at the anchor teeth<br />
can be desirable, because it helps to prevent unwanted<br />
movement <strong>of</strong> those teeth. Even so, a problem lies in the<br />
5