From Volume 8, Issue 3, July 2015 | Pages 92-100
Transpalatal arches (TPAs) are widely used in clinical orthodontics. The versatility of the TPA makes it an extremely useful adjunct to both conventional and contemporary fixed appliance treatment. This paper describes the history, the variety of designs and the clinical steps and laboratory methods for TPA construction. The range of clinical applications of the TPA are presented using a series of cases.
The transpalatal arch (TPA) is a stainless steel wire connecting the maxillary molars during fixed appliance orthodontic treatment to assist with anchorage reinforcement. Although, in most countries, the term lingual arch is reserved for the lower arch, in North America, auxiliary arches used for both the lower and upper dentition are termed lingual arches.
The TPA was originally described by Robert Goshgarian.1 It is constructed from 0.9 or 1.25 mm stainless steel wire and crosses the palate to connect one molar or premolar to a contralateral tooth. This connection can be fixed by welding/soldering or be removable by insertion into a lingual sheath on the molar bands. These molar band sheaths are known as Wilson tubes2 or Mershon attachments.2,3 A modification of the attachment involves bonding the palatal wire directly to the lingual surface of the molars.2
Although the TPA does not provide absolute anchorage, it is used as an adjunctive appliance during orthodontic treatment to control anchorage in the vertical, transverse and sagittal (antero-posterior) dimensions. The extent of anchorage it provides depends on the design and the anatomical/morphological features of the palate. Where the TPA is modified by the addition of acrylic for the palatal vault (see Nance arch below), the depth and width of the palate contribute to the potential increase in anchorage. Logically, a shallow and wide palate has less anchorage potential than that of a deep-vaulted palate.4
The Nance appliance or Nance palatal arch (NPA) was one of the earliest modifications of the TPA, first described in 1947.5 The palatal wire is welded/soldered to the molar bands and is connected anteriorly by an acrylic button positioned in the highest part of the palatal vault resting on non-compressible mucosa. The button is made of heat-cured, cold-cured or light-cured acrylic. Light-cured composite has also been used.5 Modifications of the wire design and minor alterations in the position of the button can also be made (Figures 1–3).
The lingual arch was used extensively by Nance in the mid-1940s.6 The same 0.9 mm diameter wire is used for construction as with the palatal arch (Figure 4). Again the stainless steel wire can be either welded/soldered to molar bands, inserted into molar sheaths (removable), or bonded directly to the lingual surface of lower molars. Modifications in wire construction (Figure 5) allow direct attachments of exposed teeth to the arch to improve patient comfort and allow initial traction. The wire diameter can be increased where greater rigidity is required. However, Owais et al showed that, when using 1.25 mm wire compared with 0.9 mm wire, the increased wire stiffness results in increased forces on the lower incisors and first molars.7 Consequently, more proclination of the incisors and loss of the Leeway space loss may occur.7 Additionally, the increase in wire stiffness of the lingual arch results in higher cementation failure and wire breakage.7
The clinical steps involved in construction of all types of transpalatal and lingual arches are similar. It is best to fit the appliance before extractions are undertaken or active orthodontic treatment is commenced to avoid tooth movement which can make fitting of the appliance difficult, with the potential loss of vital space. The traditional clinical steps include prior placement of separators for 5–7 days8 in order for molar bands to fit well.
When selecting bands, it is a common practice to choose bands one size bigger since the lumen of the band can reduce during the laboratory welding and soldering procedures. An impression is then taken over the bands; these are repositioned in the impression, which is decontaminated before transporting to the laboratory. When the anchor molars are rotated, this makes band placement difficult and so four options are available:
TPAs have great versatility, acting as a stand-alone appliance or as an adjunct to fixed appliances. Owing to the versatile design, TPAs can provide passive and active orthodontic forces in all three dimensions (Figure 6):
TPAs and lingual arches can be used to provide transverse anchorage and arch width stabilization in clinical situations, as when aligning palatally impacted maxillary canines (Figure 7).9 The TPA is also effective as a holding appliance or as a retainer after active maxillary expansion with a quadhelix or rapid maxillary expansion (RME) (Figure 8). For patients with an alveolar cleft, the TPA can also be used to maintain the form of the expanded arch immediately before alveolar bone grafting (Figure 9).10
Another traditional use of TPA in the transverse dimension is as an adjunctive appliance in segmental Burstone arch (intrusion) mechanics used to correct anterior deep bites or to decompensate the anterior segment (in the case of a skeletal anterior open bite) before proceeding with a two piece Le Fort I osteotomy (Figure 10).11 The TPA counteracts the buccal tipping of the crown of the molars during intrusion of the anterior teeth.
A TPA in combination with a fixed-functional appliance can also be used to counteract the buccal forces produced by Class II bite correctors, such as the Twin Force Bite Corrector (Ortho Organizers®, Ca, USA) or AdvanSync appliance (Ormco®, CA, USA) (Figure 11).12 Although TPAs have been advocated as an adjunct to headgear (to reduce the buccal tipping of molars and palatal cusp extrusion during molar distalization),13 no difference has been found between the use of headgear with or without a TPA for molar distalization.14
More recently, the use of TPA-temporary anchorage devices (TADs) combination to correct anterior open bites has been reported.15 A TPA is frequently used to control molar tipping when posterior teeth are intruded using this method (Figure 12). A further use of the TPA is in the interceptive treatment of palatally displaced canines (PDC): this has been shown in a clinical trial by Baccetti et al to be as efficient as a combination of RME and a TPA.16
The TPA can also be used as a habit deterrent for persistent thumb and digit-sucking habits (Figure 13). This requires the soldering/welding of a crib to the TPA.17 Furthermore, the requirement for bilateral space maintenance following premature loss of primary molars is an indication for the use of a TPA or lingual arch for both the upper and lower arches to prevent loss of Leeway space and potential crowding of the premolars where extractions of the deciduous molars are planned in order to harness the Leeway space, a TPA and lingual arch is also indicated. However, one of the potential problems when using a lingual arch as a space maintainer is the interference of the wire with the erupting premolars. A modification of this has been suggested which involves soldering the wire on the buccal surface of the molars and allowing it to pass along the buccal vestibule before it passes over the canine embrasure to run behind the lower incisors (Figure 14).18
TPAs can be used actively to minimally expand or constrict the dental arches in a similar way to the quadhelix appliance. In this situation, the TPA can be expanded or contracted by 3–4 mm to provide a force of around 200 gm. 19 Furthermore, TPAs can be used for distalization of the molars unilaterally or bilaterally to correct a mild Class II molar relationship. This is achieved by activating the U-shaped bend in the TPA.20 Where unilateral distalization is required, it is better to reinforce the anchor side with headgear, place torque in the archwire to make use of cortical anchorage, or use temporary anchorage devices.20,21,22,23
A TPA positioned away from the palate can produce a molar intrusive effect by the tongue, which can help in correcting or controlling any over eruption of maxillary molars (Figure 15).1 In this situation, the TPA is constructed 5 mm away from the palate. Wise et al found that, when compared with controls, a TPA can control the maxillary vertical growth although, as this was a retrospective study, the results should be treated with caution.14
A Nance palatal arch can be used to provide anchorage to distalize the molars as in part of the pendulum appliance,24 rapid molar distalization; the distal jet (American Orthodontics®, WI, Canada),25,26 Jones jig (American Orthodontics®, WI, Canada)27,28,29 and the Lokar distalizing appliance (Ormco®, CA, USA).30,31 Once distalization has been achieved, the Nance appliance is replaced by a TPA to maintain the molar position and the space gained.5
The most common use of a TPA is to minimize loss of anchorage during fixed appliance treatment. This is done by preventing the roots of the upper molars from rotating mesially as they move mesially1 and by bringing the buccal roots into contact with cortical bone (cortical anchorage), which is resistant to remodelling and therefore provides additional anchorage (Figure 16). The loop should be directed posteriorly if the TPA is to provide antero-posterior anchorage.
Recent studies that have investigated the effectiveness of the TPA for anchorage reinforcement have found that TPA is moderately successful for anchorage reinforcement when compared with other methods of anchorage reinforcement (Table 1). Correction of molar rotations to facilitate insertion of a headgear inner bow can be achieved using a TPA. It is thought that derotation might provide additional arch length. The removable TPA can produce this when the U-shaped bend is activated (Figure 17).20 In some cases, with a Class II molar and where premolar extractions are undertaken, rotating the molar mesiobuccally is required to produce a good buccal segment occlusion. The TPA may help to achieve an optimal molar relationship due to the additional space resulting from the removal of the upper premolars. Similarly, mesial or distal tipping to achieve ‘Andrew’s Class 1 molars relationship', or to correct molar distal tipping following headgear, can be achieved using a TPA.20
| Appliances | Findings | Authors |
|---|---|---|
| No appliance (control) | Mean anchorage loss of 4.1 mm and 4.5 mm was found in association with the TPA and the control group, respectively | Zablocki et al38 |
| Onplant, TADs and headgear | Anchorage loss in the TPA group during the initial alignment stage was approximately 2 mm compared to 1.6 mm in the headgear group while the anchorage was stable in the Onplant group from the start until the end of treatment | Feldmann & Bondemark39 |
| Nance and TPA appliances | Both appliances are moderately effective in preserving anchorage (anchorage loss of around 1 mm over 6 months) and there was no difference in anchorage support between the groups but TPA was well tolerated by the patient | Stivaros et al40 |
| TADs | 2.5 mm of mesial movement of the upper first permanent molars in the TPA group while the TADs group provided absolute anchorage | Sharma et al41 |
| Nance, TADs and headgear | No statistical significance between the three methods in providing anchorage | Sandler et al42 |
A recent development of the traditional TPA is the incorporation of finger or ballista springs to aid eruption of impacted maxillary canines.9Figure 18 shows several clinical applications in cases with impacted canines. The acrylic buttons in these cases are vertically positioned in the palatal vault to provide vertical anchorage and allows a ballista spring to be embedded and activated to extrude the canine (Figure 18a, b). However, the spring can be directly soldered on to the TPA and activated to extrude a deeply impacted canine (Figure 18c, d).
Lingual arches can be used to provide attachments to extrude multiple teeth after surgical exposure (eg in cases of cleidocranial dysplasia) using the Jerusalem approach,32,33,34,35 the Belfast–Hamburg approach36 and the Toronto–Melbourne approach.37 In general, all these approaches co-ordinate the timing of extraction of primary and supernumerary teeth, the surgical exposure of the permanent teeth and alignment. Figure 19 shows a 14-year-old patient with delayed eruption of multiple permanent teeth mainly due to severe arch crowding. A TPA and a lingual arch were used to provide AP anchorage and preserve the Leeway space, with the extraction of second deciduous molars to allow eruption of the second premolars. Loops in the lingual arch were incorporated to allow attachment of the gold chains.
TPAs can provide an attachment for other fixed appliance auxiliaries (Figure 20). A modified Nance appliance modified with an anteriorly positioned acrylic button can provide a fixed acrylic flat anterior bite plane for the treatment of anterior deep overbite.
These can be summarized in Table 2.
| Complication | Comment |
|---|---|
| Breakage and cement failure | Breakage and cementation failure is approximately 2% and 30%, respectively, and common with large diameter wire wires43,44,45,46 |
| Oral hygiene difficulties | Nance appliances result in deterioration of oral hygiene beneath the acrylic plate leading to inflammation of the palate47 |
| Unwanted changes in lower arch width with the lingual arch | Increase in intercanine width as the canines migrate distally and the proclination of lower incisors as a result of the reciprocal force on the lingual surface of lower incisors48,49,50,51 |
| Poor patient tolerance | Nance appliance in comparison to the standard TPA and other method of anchorage reinforcement40,42 |
| Impinging on the palatal mucosa as the molars move mesially | The loop of the TPA can cause palatal trauma (Figures 21, 22) |
| Increase of risk of root resorption | As TPA positions the roots of the anchor units against the cortical bone plate52 |
| Frequent need for TPA removal and recementation during space-closing mechanics | In order to overcome this potential problem, a combi/TPA/Nance appliance can be used (Figure 23). The Nance button portion of the arch can be removed during space closure, whilst leaving the TPA portion in situ to provide some A-P anchorage53 |
Transpalatal, Nance and lingual arch appliances have a variety of uses in clinical orthodontic treatment. Their uses range from interceptive applications to anchorage management for challenging malocclusions. They can be custom-made, ready-made, fixed or removable.
