Synchronous straight-wire part 2: application

Case study (Figure 1 a–e)

A male patient aged 14 years, 8 months with average oral hygiene with a Class I malocclusion on a Class I base, increased MMPA and vertical lower facial dimension, had moderate crowding in both arches and lateral incisor crossbites. The upper and lower left first molars had a poor prognosis while the third molars presented good form and position.

The treatment plan was as follows:

The required movements were as follows:

The required movements are charted on the ACT (Figure 2).

The forces required for configuration are shown in Figure 3. In the lower arch, elastic traction from molar to canine will give a good balance of movement of canine retraction and molar advancement. Asymmetrical movement of the lower incisors can be facilitated by coil spring, and elastic traction from the wire to the lower right lateral incisor will advance the incisor into the space as it becomes available. In the upper arch, elastic chain can be used in the same way but space loss will be much more rapid in the upper molar region. Therefore, it is important to ensure that the balance of forces is applied so that the canines retract well before the molar space is lost. Coil spring is therefore used to distalize the canines and is supplemented with inter-arch traction to retract the upper canine reciprocally and advance the slower moving lower second molar. Elastic traction to the upper lateral incisors will advance them into their final positions as their space opens and counteract any anterior movement of the upper incisors under the influence of the coil spring.

By these means the appliance is fully configured to move all the teeth into their final positions concurrently to produce rapid synchronous movement.

Treatment

Visit 1

Fit: The appliance is fitted in accordance with the ACT (Figure 4). 0.017″ × 0.025″ thermally activated nickel titanium wire placed.

Visit 2

Fit + 9 weeks: (Figure 5).

Primary focus: canine and molar relationship maintained during canine retraction. Lower centre line correcting.

Secondary focus: space available to align lateral incisors.

Tertiary focus: molar space >50% closed in upper arch and 25% closed in lower arch. Mechanics: reactivated elastic and coil components.

Visit 3

Fit + 17 weeks: (Figure 6)

Primary focus: canine, incisor and molar relationship maintained during canine retraction. Canines over retracted, lower centre line over corrected.

Secondary focus: subsidiary teeth corrected.

Tertiary focus: upper molar space closed; lower 60% closed.

Mechanics: elastic chain placed to close residual spacing; inter-maxillary traction stopped.

Visit 4

Fit + 26 weeks (Figure 7)

Primary focus: appliance fracture upper right second molar: crossbite developed.

Secondary focus: subsidiary teeth corrected.

Tertiary focus: residual space closure required.

Mechanics: bracket re-attached to re-align upper molar; elastic chain replaced to close all residual space.

Visit 5

Fit + 31 weeks: (Figure 8)

Emergency visit upper right second molar tube fracture.

Primary focus: crossbite persists; all space closed in upper arch.

Secondary focus: subsidiary teeth corrected.

Tertiary focus: upper lateral incisor torque to be expressed and lower molar space persists.

Mechanics: upper second molars banded; 0.021″ × 0.025″ thermally-activated nickel titanium wire placed in upper arch to express torque and prepare for expanded steel wire to correct crossbite. Elastic chain in lower arch to complete space closure.

Visit 6

Fit + 35 weeks. (Figure 9)

Primary focus: incisor and canine relationships corrected, centre lines corrected; lower molars tipped mesially.

Secondary focus: subsidiary teeth corrected.

Tertiary focus: all space closed, upper lateral incisors torque expressed.

Mechanics: expanded 0.021″ × 0.025″ upper and contracted 0.017″ × 0.025″ lower steel archwires for crossbite correction and molar uprighting.

Visit 10

Fit + 54 weeks (Figure 10)

Primary focus: key teeth corrected.

Secondary focus: subsidiary teeth corrected.

Tertiary focus: buccal occlusion requires settling.

Mechanics: vertical buccal segment elastics.

Visit 11

Fit + 58 weeks: (Figure 11)

The applied forces have produced the required movements in 58 weeks. Mechanics: de-bond and fit retainers, bonded lower lingual retainer, upper vacuum formed retainer.

Treatment statistics

This case was complicated and efficiency was reduced significantly by breakages. With hindsight, the second molars should have been banded from the outset. This may well have saved 3–4 visits. However, first molar space of 11 mm was closed in 13 months, averaging a rate of 0.85 mm/month and, although this case did take 11 visits, it was a first molar extraction case. The old adage of the ‘extraction of four sixes doubles the treatment time and halves the prognosis’ would appear to be obsolete.

Results

A total of 40 cases, treated at the Royal Hampshire County Hospital, Winchester, were compared with three groups of cases using the SWA and the Damon SL system

The group of patients represented in Table 1 is a typical mix, with breakages, poor compliance and missed appointments contributing to decreased efficiency.

Table 2 compares the above 40 cases treated using SSW in Winchester, with 30 cases treated by Harradine³ using standard SWA (H-SWA) and the Damon selfligating (SL) bracket (H-SL) and 200 SWA cases treated by 10 specialist practitioners in the General Dental Services reported by Kelly and Springate⁴ (K+S).

SSW performs well in all areas, reducing treatment time and number of visits by a considerable margin, despite higher initial PAR scores and lower final PAR scores. Higher quality results were achieved in less time and with fewer visits, giving a TEI nearly 2 points higher than the best other group (H-SL). It is reasonable to point out here that such comparisons may not be entirely fair as the groups may not be matched and for statistical reasons may not provide fair comparisons. However, it is also reasonable to suggest that simultaneous movement is at least likely to be more efficient than staged movement, provided that it is achieved smoothly.

Discussion

Physiological and mechanical limitations govern the performance of all orthodontic treatment regimes. We can do little about the former but we can do much to influence the latter. Conventional mechanics are staged and this significantly prolongs treatment. In addition, although brackets are pre-programmed, the appliances themselves are not, they are simply fitted with the initial aim of ‘level and align’ (2-dimensional movement), and not configured to produce the required movements (3-dimensional movement). The aim of this technique is to add the concept of appliance programming for movement optimization to the SWA concept of bracket prescription, which optimizes position.

SSW aims to minimize clinical complexity. The appliance is simple, using only brackets, wires, elastics and coil-spring. There are no uprighting springs, transpalatal arches, piggy-back arches, auxiliary arches or special components of any sort and no special instruments are required.

In comparison with the high initial anchorage demands of SWA, SSW minimizes these and makes allowances for them on the ACT, so that all available intra-oral reciprocal forces may be utilized at the outset. The use of robust wires and inter-maxillary elastics to this end is not feasible with conventional bracket design and archwire progressions.

SSW allows the use at appliance configuration of 0.017″ × 0.025″ pre-curved wires for overbite reduction. This facilitates concurrent overbite reduction with all other aspects of correction. This is impossible with conventional bracket design and archwire progressions.

The system is very flexible until all major movements have been achieved and allows rapid movement. These contrast with the SWA, which progresses to rigid ‘working’ wires with high resistance characteristics before major movements are initiated. Rapidity of movement with SSW can lead to over correction and so it is wise to use the technique having acquired significant clinical experience.

SSW achieves major treatment events quickly. This may raise concerns about force levels, root resorption and pain experience. However, this technique does not advocate or use high force levels. The rapidity of treatment is a consequence of continuous co-ordinated movement by direct translation, not the counterproductive use of excessive force. Looking at the pre- and post-treatment records of cases included here, rarely did any tooth need to move more than 7 mm. Given the average treatment time of 14.1 months, rates of movement were far less than 0.5 mm per month. Clearly, movement rates are not great and there is still plenty of room for significant efficiency gains.

Orthodontic treatment options are expanding with new bracket designs and archwire materials offering ever greater choice. This is not necessarily a good thing in that these greater choices may not always work efficiently when combined inappropriately. However, it may now be time to alter the thought processes that govern our framework for designing tooth movement to make the best use of them. SSW minimizes and harmonizes appliance component use whilst maximizing efficiency by co-ordinating tooth movement in three dimensions from the outset. SSW offers an alternative methodology for progressing fixed appliance treatment by abandoning the concept of treatment staging, and introducing the concept of synchronized, simultaneous movement.

Although this paper makes comparisons with other operators and techniques which, as previously stated, may not be entirely valid, the prime intention here is not necessarily to claim the best method, but to introduce a new means of structuring our fixed appliance treatments and demonstrate clearly that simultaneous treatment events can be achieved in an orderly and logical fashion.

Summary

With the advent of new wire alloys and bracket designs, improved mechanical efficiency is possible. In addition, conventional methodology of staging treatment may no longer be relevant. Finally, with the effects of globalization being felt by us all, the drive for greater efficiency will be inexorable. This paper describes a means of synchronizing treatment events and thereby significantly improving efficiency.

Conclusions

SSW offers the following, all of which enable improved efficiency: