Comparison of Alignment Efficiency, Arch Dimensional Changes, and Passive Extraction Space Closure Between Self-Ligating and Conventional Brackets in Extraction Crowding Patients: A Prospective Randomized Clinical Trial.

OBJECTIVE

To compare the alignment efficiency, arch dimensional changes, and passive extraction space closure between between self-ligating brackets (SLBs) and conventional brackets (CBs).

MATERIALS AND

METHODS

This randomized controlled trial on 70 participants (13-30 years) with moderate to severe crowding, skeletal Class I or mild to moderate Class II malocclusions, all requiring premolar extractions, who were randomly assigned to CB (n = 35) or SLB (n = 35) groups. Baseline age, gender, crowding, and malocclusion type were recorded. Standardized 0.022-inch MBT brackets were bonded, with alignment started using 0.014-inch nickel-titanium (NiTi) archwires and monthly follow-ups. Outcomes-Little's Irregularity Index, intercanine and intermolar widths, and passive extraction space closure-were measured on blinded casts at baseline, 3, 6, and 9 months using digital calipers, with no active space-closing auxiliaries. Data were analyzed using linear mixed-effects models with repeated measures and covariates; regression coefficients with 95% CIs were reported, and p ≤ 0.05 was considered significant.

RESULTS

Over the 9-month observation period, both groups showed substantial improvement in alignment. SLBs demonstrated faster early alignment, with greater reductions in Little's Irregularity Index at 3 months in both arches (maxilla: β = -0.91, p  < 0.001; mandible: β = -0.60, p = 0.009), and in the maxilla at 6 months (β = -0.66, p = 0.005). Intercanine width increased in both groups, but expansion was consistently smaller with SLBs (β = -1.36 to -1.69 mm; all p  < 0.001). In contrast, intermolar width was greater with SLBs throughout follow-up in both arches (maxilla: β = 2.34-2.77 mm; mandible: β = 2.06-2.34 mm; all p  < 0.001). Passive extraction space closure decreased significantly over time in both groups, with no significant effect of bracket type.

CONCLUSION

SLBs showed smaller increases in intercanine width, greater intermolar expansion, and faster early alignment. However, passive space closure was similar between groups. Differences were modest and may have limited clinical significance. Trial Registration: Retrospectively registered at ClinicalTrials.gov (NCT07503314).