Effects of tooth position, magnitude, and attachment on anterior tooth movement success in clear aligner therapy: a retrospective cohort study

Objective To evaluate the clinical acceptability, at first refinement, of eight anterior tooth movement categories during Invisalign ® clear aligner therapy in adults and to assess the independent contributions of tooth position, prescribed movement magnitude, and attachment design to outcome. Materials and methods A retrospective cohort study was conducted using digital orthodontic records from 91 adult patients (mean age 37.1 ± 11.2 years; 78.0% female) treated with Invisalign at a single academic orthodontic center between 2018 and 2025. Prescribed anterior tooth movements (canine to canine maxillary teeth 13–23; mandibular teeth 31–43) meeting predefined minimum thresholds (linear movements ≥ 0.5 mm; angular movements ≥ 1.0°) were evaluated by comparing the initial ClinCheck plan with the first refinement plan. A movement was classified as clinically accepted if it did not appear as a continuing prescription in the first refinement plan. Eight movement categories were assessed: extrusion, intrusion, mesial rotation, distal rotation, buccal inclination, lingual inclination, mesial angulation, and distal angulation. Success rates were compared across tooth types, arches and attachment design using Chi-square tests. Results Rotational movements were least predictable overall: mandibular canine mesial rotation had the lowest success rate in the cohort (15.4%), compared with 50.7% in mandibular lateral incisors ( p < 0.001). Buccal inclination was most predictable in canines (maxillary 48.9%) and least predictable in maxillary central incisors (17.8%; p < 0.001). Vertical movement success was position-dependent: extrusion was highest in mandibular central incisors (12/17; 70.6%) and intrusion in maxillary canines (51.9%). Optimized attachments significantly improved lingual inclination success rates (40.9% vs. 32.9% conventional vs. 26.9% no attachment; p = 0.002). Conventional attachments outperformed optimized attachments for mesial rotation (33.8% vs. 21.8%), a finding likely confounded by case complexity, but attachment design did not significantly influence vertical or rotational angulation outcomes. Conclusion The clinical predictability of anterior tooth movements in clear aligner therapy is determined primarily by movement type, tooth position, and prescribed magnitude rather than attachment design alone. Rotations and lingual inclination in incisors represent high-risk movement categories requiring adjunctive strategies or modified patient expectations. These success rates reflect clinician-determined treatment acceptability at first refinement rather than a continuous, geometry-based measure of achieved tooth position and should be interpreted accordingly. These findings provide a movement-specific framework for evidence-based anterior aligner treatment planning. Clinical trial registration Not applicable.