[An in-vitro study of the use of palatal arches in controlling the position of the upper molars].

An in-vitro study was performed analysing the forces and moments produced by the transpalatal arches of the Goshgarian type (0.036" x 0.032" stainless steel and and of the "Precision Lingual Arch System" advocated by Burstone (0.032" x 0.032" stainless steel and 0.032" x 0.032" TMA) using an electronic force-moment gauge recently developed by Planert. The palatal bars were adapted passively, and in addition, molar expansion, symmetrical molar rotation, and buccal root torque were applied. It was found that under clinical conditions it was impossible to fabricate an absolutely passive arch wire with any of the arch types under investigation. The highest precision in applying forces and moments together with the least side-effects was possible using the low stiffness TMA version of the Burstone system.