Effects of Overcorrection on Mitigating Uncontrolled Tipping During Incisor Retraction Using Clear Aligners: Finite Element Analysis and In Vitro Experiment

The uncontrolled tipping in the treatment of incisor retraction with clear aligners is still compromising orthodontic treatment. Different countermeasures have been proposed to improve the predictability of aligners.This work inspected the biomechanics of the overcorrection in reducing the tipping angle and moment during incisor retraction with a clear aligner, with in-vitro experiments and finite element analysis. Specifically, the influence of angle, retraction distance, and the combination of both were assessed through in vitro experiments and the simulation. Further computational simulations were conducted to inspect the mechanical performance of clear aligners with different overcorrection angles for a fixed retraction distance of 0.15 mm. As the overcorrection angle increased from 0deg; to 1deg; and 2deg; for the clear aligner with a retraction of 0.15 mm, the tipping angle of the incisor decreased from 0.29deg; to 0.25deg; and 0.21deg;, and the tipping moment in the tooth root decreased from 13.60 N∙mm to 9.38 N∙mm and 6.27 N∙mm. However, the retraction force also decreased from 0.84 N to 0.73 N and 0.47 N, which leads to a trade-off and may result from the increased counteractive moment and decreased force exerted onto the tooth crown by the aligner. In conclusion, this study presents both the benefits and limitations of overcorrection strategies in reducing the tipping angle and moment during incisor retraction using clear aligners, providing biomechanical insight for the optimal design of clear aligners for improving treatment outcomes.