Predictability of Sequential Distalization of the Upper Arch Using Invisalign^®: A 3D Superimposition Study

Background: Sequential distalization of the upper arch with clear aligners is widely used to correct Class II malocclusion, but its predictability across molars, canines, and incisors is unclear. This study compared virtual planning with intraoral outcomes and identified the associated side effects. Methods: A retrospective study analyzed 80 maxillary quadrants from 40 patients with dental Class II malocclusion treated with Invisalign^® (Smart Track^® material) using a sequential V-pattern distalization protocol with Class II elastics and vertical rectangular/optimized attachments. Predicted movements were extracted from ClinCheck Pro^®. Scans at baseline and after the first approved aligner stage were superimposed on the palatal rugae using Geomagic Control X^®. Extrusion/intrusion, buccolingual movement, mesiodistal translation, rotation, angulation, and torque were measured for molars, canines, and incisors. Results: Molar distalization reached 1.80 of the 2.60 mm planned (69.2%), and canines 1.12 of 2.45 mm (45.7%) and incisor intrusion reached only 0.03 of the 1.45 mm planned (2.1%). Buccolingual molar movement was most predictable (97.4%), and molar rotation showed moderate-to-good predictability (88.4%); incisor rotation, angulation and torque accuracy were 62.2%, 53.8% and 23.2%, respectively. Molar angulation and torque were markedly overexpressed, with unplanned intrusion of 0.80 mm; canine angulation/torque were similarly overexpressed. Incisor intrusion/torque movements were least predictable. Conclusions: Predictability of sequential upper-arch distalization varied widely across tooth groups and movement types. Linear distalization was moderately to poorly predictable and rotational movements were well reproduced, but angulation/torque control were the least predictable, especially for molars and canines, with unintended molar intrusion and buccal torque. Incisor torque, intrusion, and retrusion were most underexpressed. Vertical rectangular attachments improved molar tipping control, while absent attachments and Power Ridges worsened incisor torque/translation. Clinicians should anticipate overcorrection and refinement stages to avoid false expectations based on the initial ClinCheck outcome.