Predictability of In-Office Clear Aligner at Final Canine Retraction: A Comparison of Interproximal Contact Tightness and Canine Distalization Between Virtual and Actual Outcomes in Premolar Extraction Cases

Objective: This retrospective study aimed to evaluate interproximal contact tightness (ICT) at completion of maxillary canine retraction in first premolar extraction cases treated with In-office Clear Aligner (IOCA). Materials and Methods: The study sample comprised 18 subjects who underwent maxillary first premolar extractions. All cases were treated using a multi-stage intraoral scanning protocol, followed by digital laboratory set-up for the fabrication of IOCA. Recorded data of both virtual and actual stereolithography models at completion of canine retraction were collected. The ICT between the maxillary canine and second premolar was evaluated using (1) virtual residual extraction space (VRS) and (2) actual residual extraction space (ARS). Using superimposed models, canine distalization was assessed through (1) virtual canine distalization (VCD) and (2) actual canine distalization (ACD). All measurements were performed using GOM Inspect Suite. Statistical analysis involved the Wilcoxon signed-rank test and paired t-test. Results: Interproximal contact tightness of the actual group (median 0.46 mm; 95% CI: 0.41–0.58 mm) demonstrated statistically significant larger residual space than the virtual group (median 0.11 mm; 95% CI: 0.10–0.21 mm). The median difference between ARS and VRS was 0.28 mm (95% CI: 0.26–0.42 mm). The mean VCD was significantly greater (7.41 ± 0.89 mm) than the ACD (7.18 ± 0.97 mm). Conclusion: The actual interproximal contacts were not completely closed, in contrast to the complete contact predicted by the 3D virtual setup. To prevent this remaining gap, it is recommended to perform fake interproximal stripping or tooth collision during the virtual planning stage.