Abstract
Objective
To determine whether initial lip asymmetry predicts long-term symmetry changes in patients with unilateral cleft lip and alveolus (UCLA) and to characterize patterns of region-specific morphic change relevant to orthodontic planning.
Design
Retrospective observational study.
Setting
University-based orthodontic clinic.
Patients
Among 80 UCLA patients treated between 2008 and 2023, 42 with standardized frontal photographs at two treatment stages (before active orthodontic treatment [T1] and before comprehensive orthodontic treatment [T2]) under rest and smile conditions were included.
Main Outcome Measures
Ten lip-related measures (7 linear distances, 3 angular variables) were obtained from frontal images, and left-to-right asymmetry was calculated as the difference between the noncleft and cleft sides (noncleft-cleft). Longitudinal change was defined as Δ = T2 − T1. Paired t tests with effect sizes (Cohen's dz) and false discovery rate adjustment were used, and importance scores were used to visualize the combined magnitude and robustness of changes.
Results
Overall lip symmetry tended to improve from T1 to T2 in both rest and smile conditions. Measure 2 (peak of Cupid's bow to oral commissure distance) and Measure 6 (lower lip width) exhibited negative Δ values with moderate effect sizes (dz = 0.39-0.42) in unadjusted analyses. After adjustment for multiple comparisons, no comparisons remained statistically significant; however, effect-size patterns suggested consistent, moderate improvement in symmetry in regions around the Cupid's bow.
Conclusions
Initial lip asymmetry influences long-term symmetry changes in UCLA patients. Quantitative assessment of region-specific symmetry changes may support interdisciplinary planning focused on individualized soft-tissue outcomes.
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