Efficacy of planned maxillary central incisor rotation with clear aligners: A direction-specific retrospective cohort study

INTRODUCTION: This retrospective cohort study evaluated differences between the planned and achieved rotational changes of maxillary central incisors (MxCIs) with emphasis on direction-specific rotational changes during the initial Invisalign® (Align Technology, Tempe, Ariz) treatment series. METHODS: A total of 150 MxCIs with ≥5̊ of planned rotation from 106 adult patients sourced from the Australasian Aligner Research Database (AARD) were evaluated. Pretreatment, planned, and digital models after wear of the initial series of aligners were obtained from ClinCheck® (Align Technology, Tempe, Ariz) and measured using Geomagic Control X® software (3D Systems, Rock Hill, SC). Rotational changes were classified into six subtypes: two balanced rotations (pure rotation and combination) and four hinge patterns. RESULTS: The mean planned rotation was 16.17̊±6.68̊. The mean difference between the planned and achieved rotation was 5.40̊±5.00̊ (P<0.001) and overall accuracy was 67.4%±26.8%. No pure rotations were observed; therefore, five subtypes were analysed. Accuracy did not differ significantly among subtypes (P=0.841). Overall, 71.3% of rotational changes were expressed in the intended direction; this proportion ranged from 79-100% for hinge rotations to 38% for combination rotations. Linear regression showed that interproximal reduction and attachment type did not affect accuracy, whereas higher staging velocity and increasing age reduced the accuracy of planned rotational changes (P<0.05). CONCLUSIONS: Approximately 67% of planned MxCIs rotation was achieved, and 71% of teeth rotated in the direction planned. Rotational subtype influenced whether rotation occurred in the intended direction but did not significantly affect mean rotational accuracy.