Iterative Modeling Enables Dynamic Biomechanical Simulation In Clear Aligner Therapy

The biomechanics of clear aligner (CA)-tooth interactions undergo constant variations during orthodontic tooth movement. However, due to the technological constraints, the dynamic force changes of CA remain unknown in the computer-aid design process and the predictability of space closure is not as expected. Therefore, this study aims to propose an iterative procedure to simulate the long-term biomechanical responses during extraction treatment. Radiologic/intraoral scans, in vitro mechanical testing, and viscoelastic-FEA modeling were combined with an automated algorithm to generate sequential CA models and dynamically update tooth-periodontal ligament positions for real-time biomechanical simulation. Three groups were set up and analyzed: (1) CAs alone, (2) CA with elastics between mini-screws and aligners, and (3) CAs with elastics between mini-screws and power arms The extraction spaces fully closed, with initial biomechanical responses showing similar PDL stress (4.598±0.447 E+05 Pa) across groups but significant divergence in final stages due to dual-system force transformation. As gaps narrowed, torque control increased, redistributing stress from labial crowns to labial cervixes and lingual incisal regions. Power arms reduced posterior mesial displacement by 14.6%, demonstrating optimized force control during closure. The proposed iterative algorithm achieves dynamic simulation of the space closure process in CAT based on biomechanical calculations. Notably, due to the mechanical limitations of CAs, it is difficult to achieve “absolute anchorage” even with mini-screws. Therefore, stage-specific, biomechanically guided designs are required over static morphological approaches for aligner optimization.