Effect of Operator Experience on the Predictability of Rotational and Vertical Tooth Movements in Clear Aligner Therapy: A Retrospective Observational Study

Design: Retrospective observational cohort study conducted at university and private practice setting. Objective: To evaluate whether operator experience affects the predictability of orthodontic tooth movements and the overall treatment duration in clear aligner therapy. Materials and Methods: This retrospective observational study was conducted at the Dental School of the University of Turin and in private orthodontic settings. Seventy-two patients (50 females, 22 males; median age: 24.6 years; IQR = 5.9) with mild to moderate malocclusions were included and equally distributed between two groups: 36 patients treated by postgraduate orthodontic students (Group B) and 36 patients treated by experienced orthodontists (Group E). Post-treatment digital models were analyzed to assess discrepancies between the predicted and achieved tooth positions. The accuracy of specific movements—rotation, vertical displacement, and treatment duration—was statistically evaluated using the Mann–Whitney U test. Most of these differences, although statistically significant, remained below established thresholds for clinical relevance (0.5 mm/2°). Results: Expert operators achieved significantly greater accuracy in controlling the vertical movements of the upper central incisors (p = 0.01) and the rotational movements of the upper first molars (p = 0.03), upper lateral incisors (p = 0.03), lower incisors (p = 0.001), and lower premolars (p = 0.001). In contrast, non-expert operators demonstrated superior outcomes in the control of vertical movements of the upper premolars (p = 0.01) and in the rotational movement of the lower canines (p = 0.03). Treatment duration was significantly shorter in the expert group, with a median difference of 4.1 months (p = 0.0037). Conclusions: These findings confirm the importance of clinical experience in enhancing the predictability and efficiency of clear aligner therapy, particularly in complex movements. However, the improved performance of non-expert operators in selected areas—such as vertical control of upper premolars and rotation of lower canines—suggests that conservative movement planning may also play a role in improving clinical outcomes. Overall, expert clinicians achieved more predictable tooth movements and shorter treatment durations, underscoring the value of structured training and accumulated clinical expertise in optimizing clear aligner therapy.