Comparison between the designed and achieved mesiodistal angulation of maxillary canines and posterior teeth and influencing factors: First premolar extraction treatment with clear aligners

This study aimed to compare the designed and achieved mesiodistal angulation of maxillary canines and posterior teeth (MCPT) for first premolar extraction with clear aligner treatment and identify the main influencing factors for preventing MCPT tipping toward the extraction space.A total of 21 adults with first premolar extraction were recruited. The designed and achieved tooth movement of MCPT was measured by superimposing their respective pretreatment and posttreatment cone-beam computed tomography images and compared with the designed tooth movement in ClinCheck using the paired t test and scatter plot analysis. Influencing factors, including dental arch length change, canine distalization, and initial mesiodistal angulation, were analyzed using the linear mixed-effect model.Designed distal crown tipping (second premolar, 10.73 ± 3.22°; first molar, 9.83 ± 3.60°; second molar, 7.18 ± 2.36°) significantly increased the distal inclination of the second premolar (2.50° ± 5.15°; P ＜0.001), first molar (1.07° ± 4.14°; P ＜0.001), and second (0.70° ± 3.78°; P ＜0.001). Furthermore, mesial tipping (8.59° ± 6.03°; P ＜0.001) achieved appropriate distal crown tipping of canines (-6.43° ± 5.04°; P ＜0.001). The implemented preliminary formulas showed that shortening of the dental arch length, the distance of canine distalization, and initial mesiodistal angulation were closely related to the antitipping design.Designed distal crown tipping of posterior teeth and mesial crown tipping of canines might prevent unwanted crown tipping toward the extraction space during space closure. The proposed preliminary formula could guide antitipping designs in clear aligner treatment.