Predictability of arch width changes in patients undergoing extraction versus non-extraction clear aligner therapy: A pilot study

Abstract

Objectives: This study aimed to assess the clinical accuracy of digital treatment planning by comparing arch width measurements at pre-treatment (T0), planned with ClinCheck ® software (TC), and achieved at the first refinement stage (T1) in clear aligner (CA)-treated patients with and without extractions. Material and Methods: This retrospective single-center study included 26 patients treated with CAs, divided into non-extraction ( n = 13) and extraction ( n = 13) groups. Arch width measurements were performed in the maxilla at the canine (3–3), second premolar (5–5), and first molar (6–6) regions at T0, TC, and T1. Planned expansion (TC–T0), achieved expansion (T1–T0), and the discrepancy between planned and achieved values (T1–TC) were calculated. Clinical accuracy was expressed as the ratio of achieved to planned expansion. Intra-observer reliability was assessed using the intra-class correlation coefficient (ICC). Statistical analyses were performed using paired t -tests or Wilcoxon tests ( p < 0.05). Results: Intra-observer reliability was high for all measurements (ICC >0.866). In the non-extraction group, mean planned and achieved expansions were 1.23 mm and 0.94 mm, respectively, corresponding to a clinical accuracy of 66.67%. Significant increases were observed between T0 and T1 at all measurement sites ( p < 0.05). In the extraction group, the mean planned expansion was 1.53 mm, whereas the achieved expansion was limited to 0.34 mm, resulting in a clinical accuracy of 38.92%. Planned expansions were not achieved at any measurement point, and TC–T1 differences were statistically significant ( p < 0.05). Conclusion: Digital treatment plans with CAs show acceptable clinical accuracy in non-extraction cases, whereas accuracy is substantially reduced in extraction treatments. Therefore, greater caution is required when planning expansion in extraction cases.