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

Abstract

Abstract. Uncontrolled tipping during incisor retraction with clear aligners continues to limit orthodontic treatment. Different countermeasures have been proposed to improve the predictability of aligners, such as power ridges and attachments, while their efficacy requires further investigation. This work investigated the biomechanics of the overcorrection in reducing the tipping angle and moment during incisor retraction with a clear aligner, through in vitro experiments and finite element analysis (FEA). Specifically, the influence of overcorrection angle (1 deg), retraction distance (0.15 mm), and the combination of both were assessed through in vitro experiments and the finite element simulation. Further computational simulations were conducted to inspect the mechanical performance of clear aligners with different overcorrection angles (from 0 deg to 1 deg and 2 deg) for a fixed retraction distance of 0.15 mm. As the overcorrection angle increased from 0 deg to 1 deg and 2 deg for the clear aligner with a retraction of 0.15 mm, the tipping angle of the incisor decreased from 0.29 deg to 0.25 deg and 0.21 deg, and the tipping moment at 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, indicating a tradeoff between tipping control and retraction efficiency, likely due to increased counteractive moment and the decreased force exerted by the aligner on the tooth crown. 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.