Abstract: Objective : To establish the three-dimensional finite element models of micro-implants-lingual straight wire about anterior teeth retraction; and to analyze the teeth movement tendency with different micro-implant heights for providing the biomechanical reference for clinical application of lingual orthodontics. Methods: Three dimensional model of maxilla, teeth, and periodontal ligament was obtained by CBCT scan. The palatal micro-implants between first and second molars were set respectively with different heights (4 mm, 8 mm and 12 mm) from the alveolar crest. The obtained three-dimensional finite element models of micro-implants-lingual straight wire were used to analyze the teeth movement tendency and stress changes when labial intrusion force and lingual retraction force were applied. Results: All of the anterior teeth showed a degree of buccal root torque during the retraction. With the increase of palatal micro-implant height from the alveolar crest, the tendency of the buccal root torque of anterior teeth were significantly reduced, and the change of central incisors was the most obvious compared with the lateral incisors and canines. When the height of micro-implant was 8mm, the root and periodontal ligament stress was the minimum. Conclusion: It can effectively control the anterior teeth torque during the retraction in the lingual orthodontics treatment by choosing the right height of micro-implant and applying the labial intrusion force in anterior teeth.

Key words: Lingual straight wire, Finite element model, Micro-implant, Biomechanics, Torque