Abstract: Objective: To study the displacement trend of teeth and the stress distribution of periodontal ligament by simulating the application of different attachments on the buccal and lingual sides of mandibular first molar to move 0.2 mm mesially. Methods: Mimics19.0, Geomagic Wrap2017, NX10.0, and other professional modeling software were used to establish the finite element model. Ansys Workbench18.0 software was used to simulate the application of different attachments on the buccal and lingual sides of mandibular first molars and move 0.2 mm mesially. Results: The mandibular first molars of six groups of models showed mesial lingual tilt movement, and the anchorage tooth movement mode was mainly tilt movement. Conclusion: In the process of mesial movement of mandibular first molars, the crown is mainly inclined to the mesial lingual direction and the root is inclined to the distal buccal direction. At the same time, the anchorage loss of anchorage teeth occurs. When the lingual attachment is applied, the molar moves is close to the whole movement.

Key words: clear aligners, proximal molar movement, three dimensional-finite element