Fig. 7
From: Expert consensus on the clinical strategies for orthodontic treatment with clear aligners
Different elastic tractions and biomechanical features. a A class II elastic traction is applied between the precision cut on the upper canine and the button on the lower first molar. Since the traction force (blue dashed line) passes occlusally to the center of resistance (red dot) of the upper anterior teeth, a clockwise moment (blue curved arrow) is generated. b An elastic traction is engaged between the precision cut on the upper canine and a buccal mini-implant. Likewise, a smaller clockwise moment (blue curved arrow) is generated. c One elastic traction is applied between the precision cut on the canine and a buccal mini-implant and the other one is engaged between the aligners on the incisors and a labial mini-implant. The retraction force (blue dashed line) generates a clockwise moment (blue curved arrow) while the intrusion force (yellow dashed line) offers a counterclockwise moment (yellow curved arrow). The two moments are offset by each other and the anterior teeth are retraction in a bodily movement mode
