This study investigated the effects of different mini-screw anchorage techniques on the three-dimensional (3D) movement of anterior and posterior teeth during maxillary anterior retraction with clear aligners in extraction cases, aiming to provide guidance for clinical orthodontic practice.

A 3D finite element model (FEM) was developed based on a patient who underwent orthodontic treatment involving bilateral first premolar extractions. Six mini-screw anchorage approaches were designed: no anchorage (NA), direct anchorage (DA), two types of indirect anchorage (IDA1 and IDA2), and two mixed anchorage strategies (MA1 and MA2). Using ANSYS software, the initial 3D movements of the anterior and posterior teeth were analysed, along with stress distribution in the periodontal ligaments.

Finite element analysis revealed distinct displacement patterns among the six anchorage strategies. For the anterior teeth, MA2 produced the greatest retraction of the maxillary central incisors (0.123 mm) but demonstrated insufficient torque control and notable tooth elongation (incisor extrusion 12% higher than that with DA: 0.0726 mm vs. 0.0667 mm, respectively). Posterior anchorage was best preserved with MA2, reducing anterior displacement of posterior teeth by 19.7% compared with IDA1. In contrast, DA provided superior vertical control of anterior teeth, while IDA2 showed the greatest extrusion of second premolars. Stress distribution concentrated in the cervical and apical regions of the periodontal ligament, with notable force concentration on the buccal alveolar bone of the second premolars in indirect and mixed anchorage groups.

Overall, MA2 provided more effective anterior retraction, while maintaining posterior anchorage and reducing anterior displacement of posterior teeth. However, as this benefit was accompanied by a risk of vertical loss of incisor control, additional vertical control attachments should be incorporated to achieve optimal tooth movement. Clinically, anchorage selection should be individualized, and auxiliary torque or vertical control measures may be required to optimize tooth movement outcomes.