The effects of clear aligner to move mandibular first molar distally using finite element method.

Abstract Objectives To analyze the features of tooth movement with clear aligner(CA) under different starting point and attachment settings.Materials and methods A 3D finite element(FE) model was established including mandible, dentition, periodontal ligaments(PDLs), CA and horizontal rectangular attachment. The second molar was previously positioned 3.2mm distally. Three groups were created according to attachment setting: (1)no attachment, (2)attachment on the second molar, (3) attachment on the first molar. In each group, the starting point of the first molar was 0mm(SET1), 1mm(SET2), 2mm(SET3) and 3mm(SET4) to the premolar in turn. A distal moving distance of 0.2 mm was applied to the first molar.Results As the first molar got closer to the second molar, distal displacement of the first molar, mesial displacement of premolar and labial displacement of anterior teeth increased, while the mesial displacement of the second molar decreased. When the attachment was applied on the buccal surface of the first molar, the average displacement value reached the top for the first molar(6.79e− 2mm), premolar(2.72e− 2mm) and anterior teeth(2.59e− 2mm) in SET 4. The average displacement of the second molar reached the top(3.07e− 2mm) in SET1 when attachment was placed on the second molar.Conclusions The distal displacement of the first molar resulted in an opposite movement of other teeth in dentition without additional anchorage. The effect of mesial and labial movement increased except for the second molar when the first molar moved distally. The horizontal rectangular attachment placed on the first molar produced more distal movement of the first molar crown.