Effectiveness of the attachment position in rotated premolar in clear aligner treatment: A finite element study

The utilisation of clear aligners in orthodontic treatments for correction of malocclusions has become increasingly prevalent in recent times, due to their advantages such as aesthetics, comfort and easy to use. The aim of this study is to evaluate and compare the changes in tooth, periodontal ligament and aligner with different positioning of vertical rectangular and bevelled vertical rectangular attachments in treatment of rotated premolar using finite element analysis. In the study, a three-dimensional finite element model was created, which included mandibular teeth, aligners, attachments and periodontal ligament structures. Rotational correction without attachments were compared to rotational control with two different attachments. These attachments were positioned on buccal, lingual, both buccal and lingual surfaces and 7 different scenarios were created. For all scenarios, 1.2o of aligner activation was applied. It was observed that presence of the attachment was more effective in rotational movement. The results of the analysis indicated that rotated tooth exhibited a clockwise rotation movement. The amount of displacement of rotated tooth, deformation of aligner and the stress on periodontal ligament were highest in the model with bevelled vertical rectangular attachment positioned both buccal and lingual surfaces. According to the results of the present study; it was determined that presence of attachment was effective in rotation correction, there were similar results between two different attachment types, adding bevel to the attachment and positioning the attachment buccally and lingually together increased the amount of movement in tooth, the amount of deformation in aligner and the stress in periodontal ligament.