2023, Vol. 27 ›› Issue (7): 1050-1054

Clear aligner orthodontic therapy of rotated mandibular teeth with different shapes: a three-dimensional finite element analysis

Li Huiqin1, Wang Chunjuan2, Wang Yu1, Wang Weifeng3, Chen Dinggen3, Li Na3   

Abstract: BACKGROUND: The rotation is unpredictable tooth movement in clear aligner treatment. Tooth shape can affect the efficiency of tooth de-rotation, but there is no relevant biomechanical study.
OBJECTIVE: To investigate aligner activation influencing on biomechanics of clear aligner orthodontic therapy of rotated mandibular teeth with different shapes.
METHODS: A three-dimensional finite element model of mandibular dentition-periodontium-alveolar bone-appliance with highly simulated crown shape was established based on cone-beam computed tomography and intraoral optical scanning data of an adult who had rotated lower central incisor and second premolar. The initial displacement, movement trend and von Mises stress distribution of periodontium of target teeth and adjacent teeth were analyzed when the loading of three different aligner activation of 1.0°, 1.5° and 2.0° was applied to rotated the left lower central incisor (group A) and second premolar (group B).
RESULTS AND CONCLUSION: (1) The displacement and periodontium stress of target teeth were significantly higher in the group A than those in the group B under different rotation loads. Increasing the aligner activation could improve the efficiency of tooth de-rotation to a certain degree, but the risk of periodontal tissue injury was also increased. It was suggested that aligner activation should not exceed 1.5° for the lower incisor and 2.0° for the lower premolars. (2) In group A, the displacement of meso-adjacent tooth was 65%-105% as much as target tooth. For incisor de-rotation, we should pay attention to the adverse effect on adjacent teeth. (3) During the rotation movement, mesial tipping and slightly intrusive movement of target teeth were observed, and adjacent teeth showed the trend of tipping movement, which required additional measures to strengthen the grip on three-dimensional movement of teeth.
Key words: clear aligner, finite element analysis, biomechanics, rotated teeth, lower central incisor, second premolar