CHAPTER 11 Stage II
The second stage is easy to set up and is generally the briefest of the three stages, seldom exceeding 4 months, except perhaps in enforced first molar extraction cases (see Case 10) where there may be relatively large extraction spaces to close. In non-extraction cases, it follows that Stage II may amount to little more than accurate lining up, with .020 inch archwires, prior to the final rectangular Stage III phase. Whether using Plus or Rx-1 brackets, the handling and technique throughout Stage II is the same.
Irrespective of the starting malocclusion, the second stage should begin synchronously, in both arches, as soon as the first stage objectives have been met. In practice, this means when enamel-to-enamel contact has been achieved between upper and lower incisors, above the lower incisor brackets, together with anterior alignment. At this time, in a deep bite case, the vertical battle will have been won, so that the anchorage bends can be dispensed with, in favour of conventional vertical ‘sweeps’ in the archwires, in order to maintain overbite reduction during space closure. In fact, Stage II largely follows straight-wire practice, but with the significant advantage, particularly in extraction cases, that the orthodontist can choose between protractive and retractive mechanics, according to whether or not Side-Winder ‘brakes’ are placed on the canines.
In cases where the initial overbite was not significantly increased, the premolars will have been bonded from the start of treatment, and will already have been aligned during the first stage. However, in increased overbite cases, where Begg-derived mechanics have been used in Stage I, the premolars will have been omitted, and will require to be picked up and aligned at a pre-Stage II visit.
The premolar brackets should be selected with reference to the direction of tooth tip to be accommodated within the bracket, remembering that the second premolar, in a first premolar extraction case, is the exception tooth that comes the opposite way, with mesial crown tip toward the extraction space. A full guide to selection is described in Chapter 6.
The same .016 inch high tensile stainless archwires, as used throughout Stage I, generally have sufficient flexibility to align the premolars within a 3-week interval. However, there are cases which may require additional help. If a premolar is submerged, for instance, it may not be possible to enter the rectangular molar tube at the pickup visit. It may therefore be necessary to place the archwire in the more gingival round tube, elevating it to the rectangular tube some 2 weeks later.
Another way to deal with wayward premolars is elastic thread, which can be tied through the vertical bracket slots and out to the archwire (Fig. 11.3). This is particularly effective with lingually displaced teeth. Rotated premolars can be corrected with elastomeric E-Links or chain: in the case of a mesial rotation, the elastomeric can run from bracket to molar hook, while a distal rotation will be handled in the opposite direction, routing the elastomeric to the cuspid circle (Fig. 11.4). It is seldom necessary to use lingual attachments, although these are a further option for severe rotations.
Just occasionally, we all encounter the awkward premolar that has a combination of problems, being lingually displaced as well as rotated. Although rarely necessary, the nickel–titanium ‘underarch’ is worth remembering. This can be used sectionally beneath the main archwire if the problem is unilateral (Fig. 11.5A), or one can use a full auxiliary arch, worn ‘piggy-back’ beneath the main archwire. Either way, the premolars need to align to the rectangular molar tubes, the underarch using the rectangular tube with the main archwire temporarily sitting in the round tube. At the following visit, .020 inch archwires should readily engage the rectangular tubes to begin Stage II (Fig. 11.5B). On no account should a nickel–titanium arch be used to align premolars at the end of Stage I without the security of the stainless main arch, as this would invite loss of control elsewhere, such as relapse of overbite and overjet.
As an intermediary wire between the flexible .016 inch stainless first stage archwires and the rigid but passive .0215 × .028 inch rectangular stainless archwires used during the third stage, the author’s preference for Stage II is .020 inch high tensile stainless archwires. These are stiff enough to maintain vertical and horizontal control during space closure, but are also sufficiently flexible for derotation of the first molars at the end of the stage.
It is however possible to use .022 inch stainless archwires, which will slide through the rectangular molar tubes without undue increase in friction. There may be occasional indications for using these archwires through Stage II, where the added stiffness (nearly one-third greater than .020 inch wires) can be useful:
As in Stage I, the cuspid circles serve as traction hooks. Buccal segment spacing can be closed very easily by applying elastomeric E-Links from the cuspid circles to the molar hooks (Fig. 11.6). Space closure is greatly facilitated throughout Stage II by the design of Tip-Edge brackets, as described in Chapter 3, whereby the binding that causes friction with conventional brackets is eliminated. Once again, this is because />