Comparison of the effectiveness of clear aligners and conventional brackets in correcting mandibular anterior crowding

Objective: This study aimed to compare the clinical effectiveness of clear aligners and conventional fixed appliances in resolving mandibular anterior crowding cases with Little's Irregularity Index (LDI) ≥6 mm. Materials and Methods: A total of 62 systemically healthy patients (31 treated with clear aligners and 31 with fixed appliances) were included. Pre- and post-treatment intraoral scans were obtained using the TRIOS (3Shape) system, and digital models were analyzed in Ortho Analyzer software to measure LDI, intercanine width, first and second premolar widths, first molar width, and arch length. All measurements were performed by a single examiner, and intra-observer reliability was excellent (ICC ≈ 0.95–0.99). Non-parametric statistical analyses were used to compare intra- and intergroup changes. Results: At baseline, the groups were comparable in sex distribution (male 61.3%, female 38.7%), but the clear aligner group was significantly older (25.45 ± 7.97 vs. 17.42 ± 2.55 years; p = 0.01). Baseline LDI was higher in the fixed group (10.12 ± 2.52 vs. 8.70 ± 2.23; p = 0.01). The clear aligner group showed greater palatal cusp widths at the first and second premolars at baseline (both p = 0.01). By the end of treatment, LDI decreased to near zero in both groups (clear aligner: 0.45 ± 0.69; fixed: 0.03 ± 0.06; both p = 0.01). No significant between-group differences were found in post-treatment outcomes (end-point LDI p = 0.12; all other transverse and arch-length parameters p > 0.05). Within-group changes in transverse widths and arch length were not statistically significant beyond the LDI reduction (p > 0.05). Conclusion: In patients with moderate mandibular anterior crowding, clear aligners and conventional fixed appliances demonstrated comparable clinical effectiveness, with both approaches significantly reducing the Little's Irregularity Index to minimal levels. Demographic variables such as age and sex were not determinant factors, and no significant differences were observed between treatment modalities in post-treatment transverse or sagittal dimensions. Keywords: Clear aligner, fixed orthodontic treatment, Little's Irregularity Index, digital model analysis, intercanine width, arch length.