Multi-step finite element simulation for clear aligner space closure: a proof-of-concept compensation protocol

Clear aligners have transformed orthodontic treatment; however, they exhibit limited effectiveness in closing extraction spaces due to cumulative movement errors and excessive tipping. This proof-of-concept study introduces an innovative multi-step finite element method (FEM) for simulating sequential clear aligner applications in extraction space closure. A compensation protocol, incorporating an adaptive iterative FEM, was compared with a conventional protocol, and movement precision and unintended tipping were analyzed. The results demonstrated that the compensation protocol significantly reduced tipping (≤ 1°) compared to the conventional approach (> 6°) and minimized the mismatch between crown and root movements. Additionally, the compensation protocol consistently maintained a high achievement rate, preventing the progressive loss of movement efficiency typically observed with conventional protocols. It also provided a more controlled vertical displacement, thereby reducing unwanted extrusion. Furthermore, synchronized crown-root movement contributed to more stable bodily movement, ensuring that teeth followed the intended trajectory more accurately. These findings highlight the potential of the compensation protocol in improving treatment predictability and accuracy in extraction cases. This approach enables systematic adjustment of aligner design based on actual tooth movement, offering an optimized strategy for clear aligner biomechanics and potentially enhancing clinical outcomes in orthodontic treatment.