Abstract: Objective　 To establish a three-dimensional (3D) model of maxillary molar distalization with clear aligners, analyze the initial displacement and stress distribution of the orthodontic system and find the optimal force for anterior anchorage. Methods A 3D Finite Element (FE) model of maxillary molars distalization including the teeth, periodontal ligament (PDL), alveolar bone and clear aligners were conducted to analyze the effects of molar distalization and different forces on Class II elastics. Results The distal movement of the second molar was accompanied by distal inclination, distal rotation, extrusion and lingual inclination. The anterior teeth showed labial inclination and depression, and the displacement was inversely proportional to the distance from the abutment teeth. All the anterior teeth moved backward in every group of Class II elastic. Except for applying a force of 300g on the aligner, all stress didn’t exceed the maximum magnitude for the periodontal tissue. In addition, the stress concentration in the second molar and the displacement peak was less than the elastic and tensile limit of the aligner material. Conclusion Molar distalization with clear aligners can’t completely induce bodily movement, and the anterior teeth require additional anchorage control. A Class II elastic of 100g is sufficient to enhance anterior anchorage, while applying a force of 300g on the aligner should be avoided for the health of periodontal tissues.

Key words: finite element analysis, molar distalization, anterior tooth anchorage, clear aligner