Distalization of the Mandibular First Molar with Clear Aligners: A 3D Finite Element Study

Fujia Kang^1,2Yifei Xu³Xinyan Zhao^1,2Zhen Lu^1,2Dongning Li^1,2Jiamin Zhao¹Yibao Li¹Menghong Li^1,2*Kun Qi^1,2*

• ¹Hospital of Stomatology, Xi'an Jiaotong University, Xi'an, China
• ²Xi'an Jiaotong University, Xi'an, China
• ³Air Force Medical University, Xi'an, China

Introduction: To analyze the impact of varying initial positions of mandibular first molar and attachment configurations on teeth movement by finite element analysis(FEA). Methods: A three-dimensional model was constructed including the mandible, dentition, periodontal ligaments(PDLs), clear aligners, and attachments. The second molar was initially positioned 3.2mm distally. Groups were defined: no attachment, attachment on the second molar(2nd molar ATT), and attachment on the first molar(1st molar ATT). In each group, the first molar's initial position relative to the second premolar varied(0mm, 1mm, 2mm, and 3mm). The displacement was extracted for result analysis. Results: With distal movement of the first molar's initial position, distal displacement of the first molar, mesial displacement of premolars, and labial displacement of anterior teeth increased from 9.18e-2 to 1.12e-1mm, from 1.32e-2 to 4.16e-2mm, and from 4.07e-2 to 4.69e-2mm, while mesial displacement of the second molar decreased from 4.59e-2 to 2.96e-2mm in NO ATT group. Displacement of the first molar, premolars, and anterior teeth in the 1st molar ATT group were more than that of other groups. For the second molar, the most significant mesial displacement was in the 2nd molar ATT group. Conclusion: Without additional anchorage, the distal displacement of the first molar is concomitant with the opposite movement of other teeth in the dentition. With the distal movement of the first molar's initial position, the movement efficiency of the mandibular first molar was increased. Therefore, increased step distance in precedence can be designed to enhance the overall movement efficiency.