Three-Dimensional Finite Element Analysis of Retracting Mandibular Anterior Teeth with Labial Fixed Appliances in Different Force Application and Traction Points

Objective This study aimed to employ three-dimensional finite element analysis (3D-FEA) to investigate the effects of varying microscrew implantation points and traction hook heights on the biomechanical behavior and movement of mandibular anterior teeth during retraction. Methods An adult patient requiring the extraction of maxillary and mandibular first premolars was selected from the Orthodontics Department of Urumqi Stomatological Hospital, which provided ethical approval for this study. Various models of 3D-FEA were constructed, differentiated by microscrew position and traction hook height. Finite element analysis was utilized to calculate stress levels in the alveolar bone, brackets, archwires, and the displacement responses of teeth under different force delivery conditions. Results The length of the anterior traction hook was positively correlated with the displacement magnitude of mandibular lateral incisors and canines. When the same traction hook was applied under different anchorage conditions, the maximum tooth movement in each group exhibited a comparable trend. Compared with the other two groups (mini-implant anchorage groups), Group A1 (47th tooth anchorage group) showed statistically significant displacement of the 47th tooth. The equivalent stress of the periodontal ligament (PDL) remained stable, whereas the alveolar bone stress attained a maximum when mini-screws were placed between the first and second molars (consistent with anatomical sequencing). With increasing height of the anterior traction hook, the bracket stress in Groups A1 and A2 increased incrementally; furthermore, this increase in traction hook height enhanced the control over vertical movement in Group A2. Conclusion The clinical application of microscrews as anchorage is theoretically supported, emphasizing that optimizing force application parameters and selecting appropriate anchorage sites are crucial for effective mandibular anterior tooth retraction. This research provides a foundational rationale for optimizing future orthodontic treatment strategies.