Biomechanical Response To Crown-Root Angular In Clear Aligner Therapy

The maxillary canine plays a critical biomechanical role in maintaining archform integrity and functional occlusion.The accuracy of clear aligners (CA) for canine movement depends on anatomical factors, particularly the crown-root angle (CRA).This study aims to analyze the biomechanical characteristics of canines with different CRAs under the pressure of CA. A 3D finite element model of a right maxillary arch missing the first premolar was built. Three types of canine CRA (166°, 175°, and 184°) were applied across three aligner-based movements: tipping, rotation, and intrusion.The initial displacement of CRA-varied canines and the principle stress on the PDL were quantitatively assessed. High-CRA canine exhibited the greatest displacement at both the cusp and apex during lingual crown tipping. In rotation movement, all three canines exhibited deviation in the long axis of rotation, specifically manifesting as a mesial shift in the coronal direction and a distal shift in the apical direction,with the high-CRA canine displaying the greatest degree of deviation.In intrusion movement, the high-CRA canine demonstrated the largest vertical movement and the highest apical stress concentration. The high-CRA canine demonstrates greater efficiency during lingual crown tipping and intrusion.However, this also correlates with increased biomechanical risk, such as potential root resorption or alveolar compromise. Canines with different CRAs exhibit variations in the long axis of rotation during rotation.