Finite element analysis of impacted canine disimpaction: effects of anchorage systems and T-loop gable bend angles

To compare the effects of micro-implant (MI) and transpalatal arch (TPA) combined with T-loops of varying gable bend angles on the distalization of mesially impacted canines.

A finite element model of a mesially impacted left maxillary canine was developed using patient CBCT data. Separate models combining MI or TPA with T-loops featuring α-end angulations of 0°, 15°, and 30° were created. A 1 N retraction force was applied, and canine displacement, stress distribution, and rotation were analyzed.

Increasing the α-end angulation from 0° to 30° changed canine movement from uncontrolled tipping (crown distal/root mesial) to controlled translation (concurrent crown-root distal displacement). The 30°angulation achieved the best root control, minimizing crown-root displacement differences along the X-axis. Among the tested conditions, the 30° angulation showed the most favorable root control pattern in this analysis. Greater angulation also produced lingual root torque and intrusion, maintaining root position within the alveolar bone. Both anchorage systems enabled distalization; however, the TPA group showed slightly greater canine displacement with minor mesial movement and extrusion of anchorage teeth.

Increasing the T-loop α-end angulation converts uncontrolled tipping to controlled translation by synchronizing crown and root displacement. Angulations of 15°-30°are recommended for optimal root control. While MI offers greater anchorage stability, TPA remains a practical noninvasive alternative despite some anchorage loss.