Effect of varying anchorage force intensity on upper molar distalization using clear aligners: a finite element study

This study investigated the effects of maxillary molar distalization using clear aligners and skeletal anchorage, specifically examining the influence of varying anchorage force levels through 3D finite element modeling.

Eight models were developed, systematically varying anchorage force (1.66 N and 3.34 N) from infrazygomatic crest (IZC) screws, force application site (precision cuts or buttons), and the presence or absence of vertical rectangular attachments. A 0.2 mm activation was applied between the first and second molars.

Results indicated that variations in anchorage force did not significantly alter the displacement of the second molars or anterior teeth (canines and central incisors) across the X, Y, and Z axes, provided the force application site and attachments remained constant. However, changing these variables led to observable differences in displacement. Notably, models employing precision cuts and vertical attachments showed second molar distalization, expansion, and extrusion. Additionally, canines displayed reduced mesial crown displacement and intrusion, while central incisors moved labially with less intrusion.

Overall, none of the combinations tested were sufficient to prevent some anchorage loss or unwanted tooth movement. Variations in anchorage force did not significantly affect the extent of second molar distalization or anterior anchorage loss. However, the precision cuts and vertical attachments on molars and premolars resulted in different and more pronounced unwanted displacements.