Mesial movement of upper incisors in Class II treatment

In Class II/2 cases, the upper incisors are typically too far back in the face. In the modern thinking, which is concerned more with the incisor position in the face, the Class II molar relationship (which Angle emphasized) is secondary to (he retroclined upper and lower incisors. During leveling and aligning of (he upper arch, the upper incisors move mesially, bringing them closer to the PIP, and the Angle's classification becomes Class 11/1. In adolescent treatment, this ensuing Class II/l case can normally be corrected by conventional orthodontics, but in some adult cases mandibular surgery will be required.

The required mesial change in upper incisor position is achieved mainly by tooth movement. In orthodontic cephalometry, (he SNA is used (o record (he position of the maxillary skeletal base, and therefore this may suggest that mesial movement of the maxilla has contributed to the improved A/P position of (he upper incisors. This is because 'A' point, which is a difficult cephalometric point to record, lends to follow the change in the upper incisor root position during Class 11/2 leveling (Case DO, p. 212). The perceived change in 'A' point often gives a greater skeletal base discrepancy for the ensuing Class II/l pattern than was evident in the starting Class 11/2 malocclusion.

Fig. 7.15 'A' point is difficult to measure accurately. It tends to follow changes in position of upper incisor roots during upper arch alignment of Class II/2 cases.

In practical terms, the opening stages of Class II/2 cases may be managed in two ways:

1. Upper arch treatment may be started first, with no appliance (or else only lower molar bands) placed on the lower teeth (Fig. 7.16A). After reaching the rectangular steel working wire in the upper arch, the lower appliance may then be placed, and lower leveling commenced.

2. Upper and lower fixed appliances may be placed from the outset, with an upper acrylic bite plate being worn for the opening few months (Fig. 7.16R), to free the bite and prevent damage to the lower brackets (Case DO, p. 209). As upper arch leveling occurs, the removable bile plate gradually becomes a poor fit, and can be discarded after it has served its purpose.

Upper arch leveling and aligning are achieved by proceeding through the normal archwire sequences. Opening wires are normally multistrand, because there is often a need for anterior stepping to avoid excess force on the upper incisors at the start. Upper arch length increases during the first few months, and bendbacks should be 1 mm distal to the molar tubes to allow this in most cases (Fig. 7.16C). The typical early changes may be seen on Case DO, pages 208 & 209.

Fig. 7.16A Upper arch treatment may be started first in Class II/2 treatment.

Fig. 7.16B An upper acrylic bite plate may be worn in the early months of Class II/2 correction. (Alternative methods of overbite control are discussed in Chapter 6, p. 134.)

Fig. 7.16C Bendbacks should be 1 mm distal to molar tubes during leveling and aligning to allow arch length to increase.

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