Comparison of Two methods of Transpalatal Arch and Lingual Arch Activation

The TPA and LA can be activated with two methods: the “shape-driven method” where the appliance is made to match the final tooth position and the “force-driven method” where the appliance is made to make sure the force system delivered by it at the beginning is consistent with the planned tooth movement. This study compared the two methods in vitro quantitatively with typodont teeth and multi-axis force torque transducers in all three dimensions. Results: In the TPA first order activation, with comparable Fy (force on Y axis) reading, the shape-driven activation group had a significantly higher Mx (moment on X axis) reading than the force-driven activation group. In the TPA second order activation, with comparable My (moment on Y axis) reading, the shape-driven activation group had a significantly higher Fx (Force on X axis) reading than the force-driven activation group. In the TPA third order activation, with comparable Mx (moment on X axis) reading, the shape-driven activation group had a significant higher Fy (force on Y axis) reading than the force-driven activation group. In the LA first order activation, with comparable Fy (force on Y axis) reading, the shape-driven activation group had a significantly higher Mz (moment on Z axis) reading than the force-driven activation group. In the LA second order activation, with comparable My (moment on Y axis) reading, the shape-driven activation group had a significantly higher Fz (force on Z axis) reading than the force-driven activation group. In the LA third order activation, the shape-driven activation method resulted in the exact same shape as the force-driven activation method, no comparison between the two activation methods was needed and both method yielded the same result. Conclusion: Both TPA and LA activated using the force-driven method exhibited lesser unintended side effects in first, second and third order forces and moments than the shape-driven method. As the targeted tooth movements can be helped or hindered by the side effects, clinicians can refer to the results to make the correct activations for the most efficient and effective tooth movements