Shape, Position, Dimension of Attachments in Clear Aligners: A Systematic Review

Background: Clear aligner therapy (CAT) has become an increasingly popular alternative to fixed appliances, yet its effectiveness in achieving complex orthodontic tooth movements remains limited.Composite attachments are routinely incorporated to enhance biomechanical control, but the optimal attachment shape, position, and dimension for maximizing movement efficiency are still unclear.Objective: To evaluate how the shape, position, and dimensions of composite attachments influence the efficacy and predictability of orthodontic tooth movements in clear aligner therapy.Methods: This systematic review followed PRISMA guidelines and was registered in INPLASY (INPLASY 202570109).Electronic databases including PubMed, Scopus, Cochrane Library, and ScienceDirect were searched for studies published between January 2014 and January 2025.Eligible studies included human research evaluating attachment design variables.Exclusion criteria were finite element simulations, case reports, reviews, and non-English/French publications.Nine studies met inclusion criteria.Risk of bias was assessed using MINORS for non-randomized studies and the Cochrane tool for randomized clinical trials.Results: Nine clinical studies were included.Overall, attachment design significantly influenced tooth movement predictability, although effects varied by movement type.Ellipsoid and cylindrical shapes showed favorable force distribution for extrusion, intrusion, and anterior retraction, while rectangular attachments improved torque and mesio-distal angulation.Optimized attachments enhanced rotational performance in some studies, though evidence remained inconsistent.Attachment position played a critical role: lingual placement consistently provided better torque control and reduced unwanted rotations compared with buccal placement.Larger and more prominent attachments improved force transmission but increased wear and the risk of open gingival embrasures; similarly, a greater number of attachments enhanced anchorage yet did not reliably improve rotational movements.Conclusion: Composite attachments are essential auxiliaries for enhancing the biomechanical performance of clear align-