Biomechanical effects of overcorrection design on extraction space closure with clear aligners: a finite element...

To evaluate the biomechanical effects of counterclockwise overcorrection design on extraction space closure with clear aligners (CAs) using finite element analysis (FEA).

A maxillary first premolar extraction model with attachments and CAs was constructed from cone beam computed tomography and intraoral scan data. Counterclockwise anterior overcorrection was simulated as a two-factor design: (1) overcorrection, ranging from 0° to 5°, applied at a fixed position, and (2) overcorrection applied at five different positions with a constant magnitude of 3°. Tooth displacements were analyzed to assess sagittal, vertical, and transverse biomechanical responses.

Without overcorrection, space closure exhibited characteristic excessive tipping toward the extraction site, including anterior torque loss, posterior mesial tipping, and unfavorable vertical displacements. Overcorrection of 1°-4° substantially mitigated these effects, improving torque control and vertical stability, whereas ≥ 5° compromised space closure efficiency. The position of the overcorrection axis significantly influenced the movement patterns of canines and second premolars. With 3° of overcorrection positioned anteriorly, canines exhibited extrusive movement whereas second premolars showed intrusive movement. Conversely, when overcorrection was positioned posteriorly, canines underwent intrusive movement and second premolars exhibited extrusive movement, with further reduced sagittal tipping angles.

Overcorrection in clear aligner therapy functions biomechanically like V-bends in conventional archwires, counteracting excessive tipping toward the extraction site during extraction space closure. The biomechanical outcome is sensitive to the degree and position of overcorrection, highlighting the need for individualized overcorrection strategies.