Introduced by Robert A. Goshgarian, transpalatal arch (TPA) transverses across the palate, extending from one maxillary first molar to the molar on the opposite side, with an omega loop in the midline.
The original design included a straight bar extending across the palate, hence, also referred as transpalatal bar.
Rationale
When permanent maxillary molars move anteriorly, they rotate mesiolingually around the large lingual root.
- The space between the buccal and lingual cortical plates becomes narrow anterior to the first molar roots, preventing the molar from advancing directly and limiting its movement to a rotation.
- The large lingual root contacts the lingual plate and acts as a pivot, allowing the two buccal roots to rotate mesiolingually.
The transpalatal arch reduces anterior molar movement by coupling the right and left permanent molars together, hence, preventing any possibility of rotations.
Types
TPA can be of fixed and removable type.
Fixed TPA
- Routinely used.
- Made from 0.036-inch SS wire that is soldered to the molar bands, at their mesiolingual line angles.
- Lingual extensions to the primary cuspids are often used if no molar rotation is needed and/or post-RME treatment.
Removable TPA
- Fabricated in 0.032 inch round TMA or Elgiloy wire.
- The midline omega loop is usually oriented distally with 1-1.5mm clearance in the palatal area.
Function/Uses
TPA can be used as both an active orthodontic appliance and a stabilisation/anchorage maintenance appliance during the transition of the dentition.
- Molar stabilisation: The major function of TPA in the mixed dentition is to prevent the mesial migration of the upper first molars during the transition from the second deciduous molars to the second premolars. The appliance is routinely left in place until the comprehensive phase of orthodontic therapy is completed.
- Anchorage: It is routinely used to increase posterior anchorage in maximum anchorage cases. The TPA changes the ratio of anterior retraction to posterior protraction to approximately 2:1.
- Correction of molar rotation: TPA is capable of producing molar rotations and changes in root torque by sequential unilateral activation of the appliance. It is used to derotate unilaterally or bilaterally rotated molars.
- Correction of unilateral crossbites for maxillary expansion and buccal root torque of upper molars.
- Control upper molar eruption : Intrusion TPA can provide vertical control by the intrusion of molars in high angle cases. By placing an omega loop in the mesial direction and increasing the clearance in palatal area, tongue pressure places an intrusive force on TPA, thereby preventing molars' extrusion.
Fabrication
- It is constructed using a 0.036-inch (0.9 mm) SS wire that runs across the palate, avoiding contact with the soft tissue.
- The central loop is oriented either mesially or distally.
- When used as a space maintainer, the wire is mostly soldered directly onto the bands.
- Another method uses prefabricated lingual attachments welded to the molar bands, into which the arch wire is inserted and it can be removed also.
- During cementation, TPA should be passive. If the appliance is not passive, unexpected vertical and transverse movements of the permanent molars may occur.
Advantages
- Better soft tissue compatibility: No inflammatory changes in the palate.
- Increased vertical control: TPA has the potential to control the vertical dimension of the permanent molars and prevent overeruption or tipping of the molars.
- More effective if there is bilateral premature loss of deciduous first molars.
Disadvantages
- Some patients report of food debris getting entrapped between the transpalatal wire and palate.
- Many clinicians think that it allows the teeth to move and tip mesially, resulting in space loss.
- It is far from being recommended as the first-choice appliance for space maintenance following loss of primary maxillary molars.
References
- Orthodontics Current Principles and Techniques, 5th Edition, Xubair, Graber, Vanarsdall, Vig, Elsevier Mosby.
- The Transpalatal Arch : An alternative to the Nance appliance for space maintenance, Clinical Article, Pediatric Dentistry V29/ No 3, May/June 07, Ari Kupietzky, DMD MSc, Eli Tal, DMD
- Orthodontics Diagnosis and Management of Malocclusion and Dentofacial Deformities (3rd edition), Om Prakash Kharbanda, Elsevier India (2020).
- Textbook of Orthodontics (2nd Edition), Gurkeerat Singh, Jaypee Brothers Medical Publishers (P) Ltd.
*This article is an excerpt from the above mentioned sources and Medical Sutras does not make any ownership or affiliation claims.