In day-to-day orthodontic practice, there is a need to open deep anterior bites and to close anterior open bites. The treatment mechanics for this were explained in the previous chapter. As well as attempting to achieve a normal anterior overbite, the clinician should not lose sight of the desirability of meeting goals for upper incisor exposure relative to the upper lip, as proposed by Arnett. I lowever, it needs to be borne in mind that the surgeon has a greater ability than the orthodontist to influence this aspect of correction.
F.arly in Class 11/2 treatment, considerable upper incisor intrusion occurs during the leveling process, as progressively heavier wires are placed. Later, at the rectangular wire stage, in Class II/2 and other treatments, upper incisors can be slightly intruded, either by curve in the archwire or by the use of'J' hook headgear, or by a combination of these. Upper incisors may be intruded relative to the lip line if the patient is prepared to wear a ')' hook type of headgear (Case MP, p. 146), attached to specially soldered hooks on the upper steel rectangular wire (Figs 7.26 & 7.27). The mechanics are augmented if the upper archwire has 2 or 3 mm of curve of Spee.
An attempt may be made to extrude the upper incisors relative to the lip line in the following way. A steel rectangular .019/.025 wire with 2 or 3 mm of anti-Spee curve is tied into the lower arch. An upper wire of .014 round steel is then placed, with a 3 mm positive curve of Spee. Up-and-down anterior elastics (50 gm) can then be expected to produce some upper incisor extrusion.
Figs 7.26 and 7.27 Upper incisors may be intruded, relative to lip line, if the patient is prepared to wear a 'J' hook type of headgear. Careful contouring of the metal 'J' hooks is required so that they follow the contour of the cheeks.
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