Iterative finite element analysis of clear aligner-induced bodily canine movement under alveolar bone loss conditions.

Objective: This study aimed to evaluate the long-term biomechanical effects of alveolar bone loss on 0.25-mm canine bodily movement using a clear aligner (CA) through iterative finite element analysis (FEA). Methods: Three-dimensional maxillary models with normal bone height, 2-mm bone loss, and 4-mm bone loss were constructed. An iterative FEA approach was applied to a single CA designed for 0.25 mm of planned distal movement, with biomechanical responses calculated throughout 50 sequential stages to simulate progressive tooth displacement. All components (maxilla, teeth, periodontal ligament, and CA) were assigned linear elastic properties. At each iterative stage, the forces, moments, crown displacement, tipping, rotation, and moment-to-force (M/F) ratios were analyzed. Results: Alveolar bone loss produced lower initial forces but increased initial crown displacement and tipping. Forces declined rapidly after the initial stages and stabilized at a level below 1 N. Tipping peaked early and gradually decreased, with the largest reduction observed in the severe bone loss group. The M/F ratio increased after the early stages and maintained values above 10 across all groups, thereby promoting controlled bodily movement. Final crown displacement was greatest in the normal bone group, while overall rotation remained minimal and clinically insignificant. Conclusions: Iterative FEA demonstrated that CAs produced lower forces and higher M/F ratios under periodontally compromised conditions, supporting controlled bodily movement. However, the observed excessive initial displacement underscores the need for careful clinical management to optimize outcomes.