Fig. 9

Movement trend of incisors and canines when the incisors were intruded by 0.2 mm. The sequence is A (90°), B (95°), C (100°), D (105°), and E (110°). Those in blue represent the position before the intrusion, and those in yellow represent the position after the intrusion. Blue arrows represent the direction and trend of teeth movement. The movement magnification is 50 times. I. Potential movement trend of the central incisor: When the initial IMPA was less than or equal to 100°, the apex rotated labially, and the crown rotated lingually, while the apex moved labially. When the IMPA was greater than or equal to 105°, the apex rotated lingually, and the crown rotated labially, while the root cervix moved labially. II. The potential movement trend of the lateral incisor: The movement trend of the lateral incisor was similar to that of the central incisor, but the lingual crown rotation trend was smaller and the labial crown rotation trend was more obvious. When the initial IMPA was less than or equal to 95°, the apex rotated labially, and the crown rotated lingually, while the apex moved labially. When it was greater than or equal to 100°, the apex rotated lingually, and the crown rotated labially, while the root cervix moved labially. III. Potential mesiodistal movement trend of the canine: The canine distal crown tipped with an extrusive trend, and the CR tended to move mesially. There was no significant change in the trend of canine movement with increasing IMPA. IV. Potential labiolingual movement trend of the canine: The canine crown tended to rotate lingually with the extrusion trend. There was no significant change in the movement trend with increasing IMPA