Most of the mechanical treatment procedures described for deep-bite non-extraction cases also apply to deep-bite extraction cases. These include the effects of archwire deflection, tip in the brackets, the use of bite-plate effect, the banding of second molars, the torquing effect of rectangular wires, the effect of bite-opening curves in rectangular wires, and the effects of inter-maxillary elastics.
I lowever, there are two other important factors in extraction deep-bite cases:
• With extraction cases, lower incisors are normally maintained in their position or brought to a more retrodined position. This makes the bite opening more difficult.
• If space closure is attempted before proper arch leveling and overbite control, it will lead to bite deepening.
One of the great advantages of the preadjusted appliance system is the ability to use sliding mechanics. For this reason, the majority of orthodontists are using sliding mechanics as opposed to closing loop arches. In order to effectively slide a rectangular wire through posterior bracket slots, it is necessary for these segments to be free of friction. It is therefore important to complete arch leveling and overbite control before starting space closure. This will minimize friction. When arch wires are in a deflective state due to incomplete leveling and bite opening, they cannot effectively slide through the posterior bracket slots during space closure, because of the friction.
Fig. 6.19 Class II inter-maxillary elastics can contribute to the bite-opening effect.
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