Precision adjustment of the transpalatal lingual arch: computer arch form predetermination.

Correction of widths and axial inclinations with a transpalatal lingual arch has the advantage of distributing forces across the arch, thus minimizing undesirable side effects. The proper shape of an arch to deliver the required force systems for both unilateral and bilateral width change was determined by using an analytical approach which enabled the deactivated shape of the arch to be established and drawn by computer. The transpalatal lingual arch is extremely sensitive to shape in producing a force system. The critical nature of this shape requires the clinician to understand the over-all pattern of properly forming the arch for various applications and the clinical procedures for evaluation before final insertion. The deactivated shape and the force systems for representative applications are presented; these differ significantly from the concept of the ideally shaped wire.