Initial forces acting on the maxillary teeth with aligner activation of canine distalization on the basis of different initial canine tips in vitro.

INTRODUCTION: The objective of this study was to investigate the 3-dimensional forces exerted on the maxillary teeth with aligner activation of maxillary canine distalization on the basis of different initial canine tips in vitro. METHODS: A force/moment measurement system was used to measure the forces exerted by the corresponding aligners with the same activation of 0.25 mm for canine distalization on the basis of the 3 initial canine tips. The 3 groups included: (1) group T1, with canine inclined mesially 10° on the basis of the standard tip; (2) group T2, with canine maintained standard tip; and (3) Group T3, inclined distally 10° on the basis of the standard tip. A sample size of 12 aligners was tested for each of the 3 groups. RESULTS: The canines were subjected to distomedial forces and labiolingual and vertical components, which are minimal in group T3. As the anterior anchorage for canine distalization, the incisors were mainly subjected to labial and medial reaction forces, with the most significant reaction forces in group T3, and the lateral incisors were subjected to greater forces than the central incisors. The posterior teeth mainly received medial forces, which were greatest when the pretreatment canines were distally tipped. The forces on the second premolar are greater than those on the first molar and the molars. CONCLUSIONS: The results demonstrate that attention to the pretreatment canine tip is necessary when performing canine distalization with aligners, and further work, both in vitro and clinically based, investigating the effect of the canine initial tip on maxillary teeth during canine distalization would greatly aid in better treatment protocol with aligners.