关键词: 舌侧矫治, 直丝弓, 前牙内收, 牵引钩, 微种植体

Abstract: Objective    To analyze the anterior teeth movement during en-masse retraction using lingual straight-wire appliance with combinations of different positions and lengths of power arms and mini-implants through the three-dimensional finite element method. Methods    The study was conducted from September 2024 to July 2025 at the Shanghai Ninth People's Hospital，and a 26-year-old female patient who attended the Department of Orthodontics was selected as the modeling subject. Finite element models were established for the maxillary lingual square straight-wire appliance. Two traction methods were used. The median traction was from the power arms placed on the mesial of the lateral incisors to the mini-implant on mid-palatal suture between the first and second molars. The lateral traction was from the power arms placed on the distal of the lateral incisors to the mini-implants on the palatal slopes between the first and second molars and 8 mm away from the archwire plane. Three different lengths of the power arms were designed so that the traction force line passed through the alveolar ridge，23% of root length，and 50% of root length of the central incisors，respectively. Initial movement of the maxillary anterior teeth after loading was analyzed. Results    With the increase in length of the power arms in medial traction，the central incisors changed from bodily movement to lingual root torque movement，the labial tipping of the lateral incisors increased，and the canines exhibited crown distal tipping. As the length of the power arms increased in the lateral traction，the uncontrolled lingual tipping of the central incisors decreased first and then increased，while the lateral incisors shifted from lingual tipping to bodily movement，and the canines were approaching distal bodily movement. Conclusion    When using lingual straight-wire appliance for retraction of maxillary anterior teeth，appropriate direction of traction should be designed according to clinical needs. The medial traction is conducive to the torque control and intrusion of the incisors. The lateral retraction is beneficial to the distal bodily movement of the canine while additional torque should be placed on the central incisors.

Key words: lingual orthodontics, straight wire, anterior teeth retraction, power arm, mini-implant