Comparison of maxillary arch expansion using clear aligners with and without composite attachments - A finite element study.

The influence of composite attachment geometry, placement and aligner thickness on maxillary expansion in clear aligner therapy remains inadequately understood. Therefore, it is of interest to evaluated tooth displacement and periodontal ligament stress using different attachment designs (ellipsoidal and rectangular), placements (buccal and lingual) and thermoplastic aligner thicknesses (0.5 mm and 0.75 mm). A three-dimensional finite element model of the maxillary arch was analyzed using ANSYS R18.1 to simulate expansion mechanics. Maximum displacement of the canine and first premolar was observed with a 0.75 mm aligner without attachments, while the second premolar and molar demonstrated greater expansion and higher stress concentrations with rectangular buccal attachments and 0.75 mm aligners. The null hypothesis was rejected, indicating that attachment design, placement and aligner thickness significantly affect maxillary expansion biomechanics.