How accurate is predicted root movement achieved in four first‐premolar extraction cases with Invisalign?

Objectives: This study aims to compare the achieved and predicted root movements in adults after four first‐premolar extractions and Invisalign treatment. Materials and Methods: Thirty‐three consecutive adults (22 Class I, 9 Cusp‐to‐cusp Class II and 2 Cusp‐to‐cusp Class III) from a single clinical division who completed the first series of aligners after premolar extractions were included in this retrospective study. A pretreatment cone‐beam computed tomography model was registered onto the pretreatment surface‐scanned dental model (SSDM) to locate the pretreatment root apices of the whole dentition. These were copied and transferred to the predicted and achieved post‐treatment SSDMs to acquire the locations of the predicted and achieved post‐treatment root apices. The differences between predicted and achieved root movements (DPARMs) were tested using the paired t‐test or Wilcoxon signed rank test. Results: In the anteroposterior direction, posterior root movements of maxillary and mandibular anterior teeth were poorly achieved (3.24–5.74 mm DPARMs, p <.05). In the vertical direction, roots of maxillary anterior teeth achieved greater intrusion (0.70–0.93 mm DPARMs, p <.05), while those of mandibular incisors achieved less intrusion (0.57–0.65 mm DPARMs, p <.05) than predicted. In the mediolateral direction, lateral incisor roots did not move distally (−0.65 to −0.96 mm DPARMs, p <.05), while those of canines did not move buccally, compared with the prediction (−0.75 mm DPARMs, p <.05). Conclusions: In the four first‐premolar extraction treatments with Invisalign, root movements were not achieved as predicted, particularly for anterior teeth in the anteroposterior direction. [ABSTRACT FROM AUTHOR]