Predictability of movements achieved with Invisalign® clear aligners: a retrospective study

The purpose of this study was to evaluate the predictability of tooth movements achieved with Invisalign® clear aligners and to compare the efficiency of two different types of attachments (conventional vs optimized) for rotational and extrusive movements on the upper dentition. Four hundred forty-seven upper teeth from 61 patients were evaluated. Pre- and post-treatment models were superimposed on the entire maxillary model using the 3D Slicer platform and the iterative closest point algorithm. Extrusion and labial crown inclination of upper incisors, rotation of upper canines and premolars, and expansion of the first molars and premolars were assessed and compared with the tooth movement table of the ClinCheck® virtual treatment plan. The overall predictability of movements across all attachment types was 29.5% for extrusion, 33% for labial crown inclination, 70% for rotation, and 86% for expansion. The median predictability of all movements was 65.55%. Central incisors achieved greater extrusion than lateral incisors ( p = 0.011), whereas laterals demonstrated greater labial crown inclination relative to predicted values ( p = 0.023). Premolars showed a greater predictability of movement between achieved and predicted rotation than canines ( p < 0.001). Conventional attachments achieved 1.95° more rotation than optimized attachments ( p = 0.002). While the predictability for expansion and rotational movements was satisfactory, it was less accurate for extrusion and labial crown inclination. Optimized attachments were as efficient as conventional ones for extrusive movements, but rotational movements showed better efficiency with conventional attachments.