It is important to use light force levels during the stage of space closure. Heavy forces can cause the bile to deepen in two ways:
• The canines can tip into the extraction sites causing archwire deflection and binding. The sliding mechanics then become ineffective, and the overbite deepens.
• Excessive force overpowers the incisor torque control of the rectangular wire (Fig. 6.23), particularly in the upper arch, causing distal tipping and bite deepening.
A small amount of torque added to the upper archwire in the incisor region, combined with lighter forces, is usually effective in minimizing these two bite-deepening factors.
The authors have tried various force levels during space closure and feel that a range of 150-200gm is most effective. This minimizes any tendency to unwanted bite deepening, and allows for efficient sliding mechanics and space closure. Active tiebacks (pp 256 & 257) are used to deliver a force of ibis size.
Fig. 6.24 This patient had an asymmetrical dental anterior open bite, which was related to right thumb sucking activity. Anterior open bites of this type are often not difficult to correct, provided the digit sucking is discontinued.
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