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Fig. 5.30 Upper molar expansion should be carried out by bodily movement rather than tipping. Minimal molar crossbites can be corrected using rectangular steel wires which are slightly expanded from the normal form and which carry buccal root torque.

Fig. 5.31 Teeth which are significantly out of the arch form should be left unbracketed until adequate space is provided for their movement and positioning. The above examples show space being created for lower canines (Case LB, p. 116) and upper canines (Case TC, p. 192).

EXCEPTIONS TO FULL BRACKET PLACEMENT

Placement of brackets or bands on all possible teeth is recommended at the start of most treatments. This allows for the earliest possible stabilization of arch form, and also helps control the cuspids. However, there are exceptions to full bracket placement.

Cases with unerupted teeth, or teeth significantly out of the arch form

Such teeth can be left unbracketed until adequate space is provided for their movement and positioning (Fig. 5.31). Once space is created, these teeth can be bracketed and lightly tied with elastic thread to the main archwire. Sufficient space must be opened for movement of instanding teeth so that they do not fulcrum at the contact area, causing improper root positioning. The creation of adequate space allows bodily movement of these teeth into the arch form and more correct root positioning, reducing the treatment needs in the finishing phase.

High-angle deep-bite cases in which the upper incisors interfere with bracket placement on the lower incisors

These cases are unusual, but when they occur, the upper incisors can be bracketed and the lower incisors left unbracketed at the start of treatment. After leveling and aligning have occurred in the upper arch for 2 to 3 months and the upper incisors have been slightly advanced, the lower incisors can then be bracketed. This prevents unnecessary extrusion of posterior teeth during the leveling procedure. In low-angle deep-bite cases, a biteplate can be placed at the initial bonding visit, provided the occlusion allows this.

Fig. 5.31 Teeth which are significantly out of the arch form should be left unbracketed until adequate space is provided for their movement and positioning. The above examples show space being created for lower canines (Case LB, p. 116) and upper canines (Case TC, p. 192).

RE-LEVELING PROCEDURES

It is necessary to repeat leveling and aligning procedures in many cases when using preadjusted appliances. Re-leveling is needed when newly erupted teeth are included for the first time, or when bracket and bands are re-cemented, either because of breakage or incorrect original positioning. During treatment, re-leveling should be carried out as few times as possible for treatment efficiency, but even experienced clinicians can fail to place all brackets accurately at their first attempt. During early leveling and aligning, these errors can be identified, and it is better to reposition brackets rather than making archwire bends throughout subsequent treatment.

Incorrectly positioned brackets can be repositioned when newly erupted or poorly positioned teeth are bracketed for the first time, because it is necessary to return to lighter archwires to pick up these teeth. Also, if second molars have not been banded until after a stage of treatment such as space closure or overjet reduction, brackets can be repositioned at the second molar banding visit. In this way, re-leveling can occur without loss of treatment time.

WIRE SEQUENCING DURING TOOTH LEVELING AND ALIGNING

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Historical background

Round and rectangular steel arclnvires were used with the standard edgewise appliance and during the early years with the preadjusted appliance. Round steel wires were used in sizes .014, .016, .018, and .020.

Rectangular steel wires were available in a number of sizes, with .018/025, .019/.025, and .0215/.025 being the most popular wires used with the .022 bracket slot. The authors prefer the .022 slot over the .018 slot, primarily because of the rigidity needed in (he archwire during space closure with sliding mechanics.

The .014, .016, .018, and then .020 round wire sequence was used by the authors, followed by the .019/.025 rectangular steel wire (Fig. 5.32). This wire allows for efficient sliding mechanics, unlike the larger .0215/.025 wire, which creates excess friction during space closure. Also, the .019/.025 rectangular wire shows less deflection than the more flexible .018/.025 wire.

One of the early attempts at producing archwires with greater flexibility involved twisting together strands of very small stainless steel wires (Fig. 5.33). These were referred to as multistrand wires. These wires, in sizes .015 and .0175, were used as initial wires, prior to the use of the .014 round steel wire, in cases with significant tooth malalignment.

.014

Fig. 5.32 Round and rectangular steel wires were used during the early years with the preadjusted appliance.

.015

.0175

Fig. 5.33 Multistrand wires were produced to introduce greater flexibility. They are currently used as initial wires in cases with significant tooth malalignment.

Recommended sequencing

The introduction of nickel-titanium wires provided a possible substitute for multistrand and steel round wires during the leveling and aligning stages of treatment. One nickel titanium wire could be used in place of approximately two sizes of stainless steel wires. I lowever, given their higher cost, their significance was considered questionable by many clinicians. They were also mistakenly used during procedures that required the rigidity of a rectangular stainless steel wire, such as complete arch leveling, overbite control, space closure, and overjet reduction with inter-maxillary elastics.

The development of copper nickel-titanium wires, referred to as 'heat-activated' wires, provided wires with significantly greater flexibility. As a result, these wires could be used as a substitute for three of the traditional stainless steel wires in certain situations, which was a significant improvement.

Instead of replacing wires on a per visit basis during leveling and aligning, a coolant could be applied to the heat-activated nickel-titanium (HAN I ) wire in the areas where full bracket engagement had not been achieved, and the wire could be retied for complete engagement. The normal warmth of the oral cavity produced significant activation of the wire and very efficient tooth movement. Surprisingly, patients did not seem to complain of added discomfort, probably because of the light forces that were introduced.

The archwire sequence shown (Fig. 5.34) has been employed by the authors. It has significantly reduced chairside time and increased the efficiency of tooih movement, owing to the minimizing of permanent archwire deflection.

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