Analysis of the effects of different composite attachments on anchor teeth during canine retraction with clear aligner – A three-dimensional finite element analysis

Objectives: This study aimed to assess the effects of different composite attachment designs on molars during canine retraction with aligners using the finite element analysis (FEM). Materials and Methods: Five 3D models of the maxilla, maxillary dentition with the first premolars removed, and aligners were created with the following attachments on the molars: Group 1: Horizontal rectangular attachments; Group 2: Distal vertical rectangular attachments; Group 3: Mesial vertical rectangular attachments; Group 4: Beveled ellipsoid attachments; and Group 5: Inclined rectangular attachments. Canine retraction was simulated by applying a thermal contraction of 0.25 mm (40 g force) in the extraction space, and the stresses and displacement were calculated. Results: The inclined rectangular attachment was found to cause the least molar movement with the most canine displacement. The ellipsoid attachment had the most balanced displacement and stress distribution. The distal vertical attachment had the least favorable properties. Conclusion: Inclined rectangular attachment is most favorable for maintaining anchorage in maximum anchorage cases, while the ellipsoid attachment can be used in maximum to moderate anchorage cases. However, attachment design is not a substitute for good treatment planning, and proper understanding of reactionary forces and overcorrection will be required to achieve ideal results.