Upper incisal torque movement with clear aligners: A three‑dimensional finite element analysis.

Area of Science:

• Orthodontics
• Biomaterials Engineering
• Dental Mechanics

Background:

• Torque movement is a significant challenge in clear aligner therapy (CAT).
• Understanding incisor torque mechanics is crucial for improving CAT efficacy.

Purpose of the Study:

• To analyze incisor torque movement under varying aligner trimming line designs.
• To investigate the influence of trimming line morphology on torque control using 3D finite element analysis.

Main Methods:

• A 3D finite element model of adult maxillary dentition was created from CBCT data.
• Clear aligner therapy (CAT) models with scalloped, straight, and extended trimming lines were simulated.
• Palatal root torque was applied to incisors with varying centers of rotation (COR) from the incisal edge (0-5 mm).

Main Results:

• Incisors showed uncontrolled palatal tipping when COR was at the incisal edge.
• Extended trimming lines generated more labial-cervical stress and less root displacement.
• Moving the COR away from the incisal edge shifted movement from tipping to controlled palatal root torque.

Conclusions:

• Extended trimming lines are beneficial but insufficient for achieving predictable palatal root torque in CAT.
• Optimizing the center of rotation (COR) in the setup is essential for predictable incisor torque movement.