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. 2022 Aug 1;23:26. doi: 10.1186/s40510-022-00421-8

Fig. 1.

Fig. 1

Three-dimensional finite element model for incisor retraction in a case involving 1st premolar extraction. a Maxillary arch with 1st premolar removal with attachments on the vestibular surfaces of the crowns and a geometric model of the clear aligner. b Different axial inclinations of the upper central incisor (U1-SN = 105°; U1-SN = 110°). c The position and size of the power ridge