Planned and achieved orthodontic tooth movement and labiolingual inclination changes of mandibular incisors during nonextraction space closure with clear aligners: A retrospective cohort study.

Introduction: The study aimed to determine the center of rotation and the type of orthodontic tooth movement (OTM) of the mandibular central incisors (Cis) and lateral incisors (Lis), and the efficacy of achieving planned labiolingual incisor inclination changes after nonextraction space closure (NESC) with the Invisalign (Align Technology, Santa Clara, Calif) appliance.

Methods: Digital study models of initial, planned, and achieved treatment outcomes were obtained from the Invisalign treatment planning facility, ClinCheck. Vectors analogous to the long axes of the incisors were generated using Geomagic Control X (version 2022.0: 3D Systems, Cary, NC) metrology software. Intersecting vectors represented the incisors' center of rotation, whereas measurement of the vectors to a reference y-plane enabled determination of incisor labiolingual inclination.

Results: A total of 166 mandibular incisors from 42 patients satisfied the inclusion criteria. The achieved mean (standard deviation) OTMs were 41.4% (23.6) of those planned. Translation was the least successful OTM, with 7.6% of Cis and 8.3% of Lis translating as planned. Planned retroclination resulted in overexpression of 151% for CIs and 165% for Lis. The accuracy of planned proclination was low, with only 16.7% of CIs and 25.8% of Lis proclining as planned, whereas the remainder retroclined instead.

Conclusions: Less than half of the planned OTM for the mandibular incisors during NESC was achieved. Planned retroclination was overexpressed, and most of planned proclination resulted in retroclination. Clinicians should consider these findings when planning NESC treatment with the Invisalign appliance.