From Volume 11, Issue 4, October 2018 | Pages 126-132
The 2D lingual appliance is a popular choice for achieving cost-effective and timely results in carefully selected cases and with the minimum aesthetic impact. This article will describe how to use the appliance and highlight particular areas where introducing it into your clinical practice may be particularly beneficial.
The 2D lingual appliance1 can be a good treatment option for patients seeking discreet orthodontic treatment. The system employs the use of low profile, self-ligating brackets which can be bonded directly. The lack of a rectangular slot means that only first and second order movements are possible, which limits its application for comprehensive treatment. The low friction mechanics, the simplicity of the brackets and their ease of use certainly offer a cost-effective adjunctive treatment. The following article highlights ways in which the 2D appliance can be a useful addition to the armamentarium of the clinician.
Most 2D brackets consist of a simple self-ligating bracket with two distortable clips on the lingual surface to contain the wire. The two clips are adjusted to allow vertical insertion of the archwires and then are crimped shut with a Weingarts plier to ensure engagement of the wire.
The clips are ‘self-ligating’ in that no modules are required, with tooth alignment occurring with the increase in archwire dimension, up to a maximum of 0.022” diameter.2
Medium twin brackets are useful for relapse cases where a power chain is not needed, but also comfort is a priority. Where greater rotational control is required, for example on maxillary central incisors, larger twin brackets can be used, and where teeth are severely crowded or rotated and physical access is a significant issue, single wing brackets are used to initiate treatment. In cases requiring space closure or significant derotational requirements, the medium twin bracket with a gingival hook can facilitate the application of a power chain. Finally, molar attachments can be added lingually where the appliance needs to be extended to the molars (Figure 1).
The total profile height of the brackets is 1.3 mm, which means that the archwire is close to the lingual tooth surfaces, and this low profile is conducive to patient comfort, acceptance of the appliance, and more efficient biomechanics.
The opening of the 2D lingual bracket is simply done by the use of a special explorer mechanically deforming the clips to their open position. The force is always applied towards the bracket base to avoid bracket debonding (Figure 2).
Following insertion of the archwire, the bracket clip is closed using a Weingarts plier with the outer beak being closed against a cotton wool roll held against the labial aspect of the teeth to protect the enamel. The clips are designed to withstand their opening and closing up to 20 times before fracture of the clip occurs.
2D lingual appliances are placed directly, thereby avoiding the need for a laboratory set-up with the associated costs that this incurs.3 Site of bracket placement is sometimes predetermined, for example due to lingual surface morphology (Figure 3), or in the maxillary arch where an increased overbite dictates more gingival placement, however, in general, positioning is down to clinician choice.
Where possible, brackets should be placed on the lingual aspect of the clinical crowns, parallel to the long axis of the tooth and in the centre, mesio-distally. From the slot to the incisal edge or occlusal ridge, placement usually ranges between 3–5 mm but needs to be consistent for each patient.4 Lingual bracket-placement tweezers are available to assist. Owing to the relatively small sizes of the brackets, especially where a single wing alone is engaged, force levels are kept low due to increased inter-bracket distances.5
Biolingual wires are pre-formed, mushroom-shaped lingual archwires and are available in five different shapes and with four different wire dimensions. These are all sized with the clear acetate template provided.
Titanol wires are also available (0.012”, 0.014” and 0.016”) and first order bends are added, either through overbending in the martensitic phase and then gently heating the wire with a flame to regain its austenitic phase, or through bending the wire with a Hammacher triple beak fine tip plier.
The lack of individuality in the 2D bracket base can mean that first order finishing bends may be required at the end of treatment and this is typically undertaken with 0.016” stainless steel archwires.
Once in situ the archwires can be secured by annealing the archwire ends or cutting them flush and placing composite stops in the inter-bracket spans.
An advantage of the 2D lingual appliances is the ability to bond brackets directly, thereby avoiding third party laboratory costs.
One of the authors (TH) undertook a personal audit of 32 dualarch and 21 single-arch treatments. The average length of time in treatment was 12 and 10 months, respectively, and the average number of appointments was 10 and 9. In the case of the dual-arch treatments, an average of 5 brackets were intentionally repositioned during the course of treatment and one was replaced due to loss or fracture. In the case of singlearch treatments, this was 2 and 1 brackets, respectively. On average, 8 brackets were placed from first premolar to first premolar in both arches, and 4 aligning and 2 stainless steel archwires were used overall in dual-arch treatments, whilst 3 aligning and 1 stainless steel archwires were used in single-arch treatments. Therefore, as of May 2017, based on these audit results, the cost of materials for dual-arch and single-arch treatments were approximately £280 and £150, respectively.
Clinical indications include the following:
The 2D appliance can be an ideal discreet appliance to use anteriorly where the treatment goal is alignment. The more complex aspects of a malocclusion, for example space creation or space closure, can be managed with a sectional, labial, pre-adjusted edgewise appliance being placed out of the aesthetic zone.
An example of a hybrid treatment is shown in Figure 4. Early loss of the lower left second deciduous molar had resulted in lingual crowding of the lower left second premolar. After a discussion of all options it was decided in the first instance to manage the case on a non-extraction basis, uprighting the teeth that had tipped into the site of the lower left second premolar and then aligning it. This was deemed the most complex aspect of the malocclusion and the rate limiting step, so treatment began here with a sectional labial appliance creating space to align this premolar. As treatment progressed, a 2D appliance was bonded anteriorly in both arches to complete alignment with the use of Mini-molds6 to settle the occlusion to completion.
When adults with increased overbites attend for orthodontic treatment this can make placement of appliances difficult. Where the overjet is positive and lingual appliances are placed in both arches, in deep bite cases, occluding onto the maxillary brackets may cause issues with both appliance damage in the upper arch and discomfort. To avoid problems, bite planes can be added to protect the anterior dentition temporarily and provide posterior contact, but where a labial appliance is fitted in the upper arch, the use of a directly bonded 2D lingual appliance in the lower can eliminate all occlusal interferences at the same time as allowing alignment to be achieved.
In the case shown in Figure 5, the patient requested alignment of his Class II division 2 malocclusion, which was complicated by the significantly increased overbite present. By placing a ceramic, labial, pre-adjusted edgewise appliance in the upper arch and a sectional 2D appliance in the lower alignment, a result could be achieved with minimal occlusal interference or discomfort for the patient.
The time it takes to derotate a tooth during orthodontic treatment can at times be unpredictable and more problematic than first anticipated. Lower incisors, in particular where rotated towards each other, can be a challenge to align from the labial aspect. Although there is a need for full effective labial ligation, the depth of the brackets can make this difficult due to the reduced inter-bracket distance.
The patient in Figure 6 was having her Class II division 1 malocclusion comprehensively treated with the loss of upper first premolars and pre-adjusted edgewise appliances. One year into treatment and a 0.019” x 0.025” stainless steel maxillary archwire was in situ and space closure and overjet reduction had commenced. At the same time, in the lower arch both lower central incisors remained rotated so a decision was made to remove the labial archwire and fit 2D lingual brackets on the lower 6 anterior teeth. The larger inter-bracket span between the brackets on the lingual aspect of the lower central incisors, coupled with the reduced friction of the archwire in the self-ligating 2D brackets, resulted in alignment of the incisors in just one visit with a lower 0.014” Titanol lingual archwire. This allowed for subsequent resumption of labial treatment to case completion.
Aligner type appliances are a popular and evolving treatment modality with advancements being made all the time in their design and use. The efficiency of their use depends on a variety of factors including the delegation to assistants of:
Sometimes, both patients and clinicians can be impatient about the rate of tooth movement, especially extrusive movements and derotation of teeth. 2D lingual brackets can provide an inexpensive method of assisting in aligner treatments either prior to aligner delivery or afterwards.
In the first case, the patient was already in aligner treatment for 14 months when a lower sectional 2D lingual appliance was used to extrude the lower right central incisor (Figure 7). This treatment was then completed in a further 4 months.
In the second case, a sectional 2D lingual appliance was placed to complete efficient incisor derotation of the upper right canine, upper right lateral incisor and the lower left central incisor at the end of the initial series of aligner trays, rather than opting for additional aligners and refinement (Figure 8).
Aligner treatments can also be assisted with a supplemental 2D lingual appliance when there are treatment sequelae that are unanticipated, such as the development of ‘black triangles’ at the gingival margin following tooth alignment.
In the case illustrated in Figure 9, significant spaces opened up under the contact points of the lower incisors mid-treatment and, rather than manage with refining aligners, a sectional 2D lingual appliance was placed. With a little judicious interproximal reduction, these spaces could then be closed with relative ease using an elastomeric chain.
For some patients, the option of orthodontic treatment to align their teeth was previously not considered and veneers, both porcelain and composite, have been provided. Fortunately, the dental profession has moved away from this practice more in recent years, either as a consequence of adverse sequelae of undertaking more aggressive cosmetic work, following collective introspection,7 or due to the greater uptake amongst the adult population of orthodontic treatment.8 Those who have had this treatment, however, can present requesting orthodontic treatment at a later stage and, when this occurs, labial appliances can be an issue both in terms of adhesion to labial restorative materials, the aesthetic impact of the appliances and the difficulty in progressively reducing the bulk of labial veneers as teeth are re-aligned and reshaped to the correct bucco-lingual dimension.
The patient in Figure 10 had previously had a veneer placed on the upper right central incisor and a crown, that had required recementation a couple of times in recent years, on the upper right lateral incisor. She was unhappy with the height, mesio-distal width, buccolingual dimension and colour of the upper right central incisor and was wanting to have the crown replaced on the upper right lateral incisor. The 2D appliance offered a good aesthetic solution allowing for progressive reduction of the veneer as the tooth was aligned. Veneer removal revealed no enamel loss so only a new crown on the upper right lateral incisor was required.
The low start-up and inventory costs means that the 2D lingual appliance is ideal for practitioners who mainly use fixed labial appliances and clear aligners, but have the desire to incorporate a lingual appliance into their treatment armamentarium, for cases requiring a limited amount of tooth movement.
