Finite Element Analysis of Torque Mechanics in Clear Aligner Therapy With and Without Skeletal Anchorage

Introduction Torque control of maxillary incisors is essential for esthetics and stability. In clear aligner therapy, torque expression is often unpredictable due to material and design limitations. Finite element method (FEM) analysis offers insights into optimizing aligner biomechanics. Objectives To evaluate the torque mechanics of maxillary incisors during anterior retraction with aligners alone and in combination with auxiliaries, including skeletal anchorage. Methods A cone beam computed tomography-derived finite element model of the maxilla and dentition was constructed. Five configurations were simulated: D1—aligner only, D2—aligner with ellipsoid attachment, D3—aligner with power ridge, D4—aligner with labial elastic from a mini-implant, and D5—aligner with linguoincisal elastic from a mini-implant. A 100 g bilateral retraction force was applied. Crown and root displacement of maxillary incisors and von Mises stress distribution in cortical and cancellous bone were analyzed. Results D1 exhibited uncontrolled tipping with a crown-to-root ratio of 411.11. D2 improved displacement (ratio 3.57), while D3 showed limited root control (ratio 214.81). D4 demonstrated a favorable root-dominant translation pattern (ratio 0.20) with maximum root displacement and highest but physiologically acceptable stress values. D5 also achieved favorable torque control (ratio 0.31) with slightly lower stress compared to D4. Conclusions Within the limitations of a single-anatomy proof-of-concept FEM model, the study shows that clear aligners alone are insufficient for effective torque expression. The addition of skeletal anchorage with elastics significantly enhances root control, with labial mini-implant-supported mechanics providing the most favorable outcomes. This hybrid approach expands the biomechanical efficacy of aligners in complex cases.