Treatment Predictability of Two Clear Aligner Systems: A Retrospective Assessment of Invisalign Versus Eon Aligner

Background/Objectives: To compare the efficacy of two aligner systems (Invisalign and Eon Aligner) across multiple linear and angular movements. Methods: A total sample of 80 patient cases (n = 40 in each group) was recruited retrospectively. Per case, 3 digital models were retrieved in the form of stereolithography (STL) files. Predicted and achieved tooth movements were measured using the 3Shape Clear Aligner Studio. Initial models were aligned on the predicted and achieved models to create superimposition. Differences in measurement between pre-treatment, predicted, and post-treatment scans were measured. Agreement between the two, Invisalign and Eon, was measured using the interclass correlation coefficient (ICC). Results: Both Invisalign (ICC = 0.82; 95% CI 0.66, 0.9) and Eon Aligner (ICC = 0.75; 95% CI 0.53, 0.87) have shown good agreement when calculating the average differences between the achieved and predicted interpremolar width values. Similar results were found for both intercanine width values (Invisalign: ICC = 0.96; 95% CI = 0.93, 0.98 vs. Eon Aligner: ICC = 0.98; 95% CI = 0.97, 0.99). In Eon cases, good to excellent agreement between the achieved and predicted models was observed for lateral (ICC = 0.89; 95% CI = 0.79, 0.94) and central (ICC = 0.93; 95% CI = 0.87, 0.96) mesiodistal rotations. Conversely, Invisalign displayed moderate strength of agreement for the lateral (ICC = 0.68; 95% CI = 0.40, 0.83) and central (ICC = 0.70; 95% CI = 0.44, 0.84) mesiodistal readings. While both aligners demonstrated some level of predictive capacity towards horizontal movements, they were unreliable in predicting vertical movements. Differences in magnitude of change between initial and achieved values between Eon and Invisalign were noted only for certain teeth in the case of horizontal and vertical movements. Conclusions: Both clear aligner therapy systems were able to achieve satisfactory outcomes in terms of inter-premolar and intercanine width changes. Eon Aligner, on the other hand, outperformed Invisalign in terms of rotational accuracy and horizontal movement precision. Notably, both systems demonstrated poor predictability for vertical movements and suffer from significant systemic bias requiring over-correction.