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Updated: Jul 9, 2026
Quantitative Assessment Protocol for Facial Soft Tissue Volumetric Changes with Stereophotogrammetry
Published on: December 9, 2025
Three-dimensional evaluation of lip changes before and after bracket debonding in patients with different vertical
Yongjie Fan1, Qiang Wang2, Xin Lv3
1Department of Orthodontics, The Fourth Affiliated Hospital of Inner Mongolia Medical University, No. 24 Qingshan Rd, Qingshan District, Baotou, Inner Mongolia, 014030, China. 13947240089@163.com.
Background:
The objective of this study was to quantitatively evaluate changes in lip morphology before and after bracket debonding in patients with different vertical skeletal patterns using 3D structured light scanning.
Methods:
285 patients (110 males, 175 females) who completed orthodontic treatment and debonding at an orthodontic clinic in China between June 2024 and September 2025 were classified into hypodivergent (FH-MP ≤ 22°), normodivergent (22°< FH-MP < 32°), and hyperdivergent (FH-MP ≥ 32°) groups based on the mandibular plane angle (FH-MP). Three-dimensional facial scans were obtained before (T0) and after (T1) debonding, and 17 lip-related parameters were measured. Linear and angular changes were compared within and between groups.
Results:
Within-group analysis showed that all skeletal pattern groups exhibited significant changes in the nasolabial angle, the mentolabial angle, the upper and lower lip prominence, the upper and lower lips to the E-line, and the commissure depth after bracket debonding. The upper lip position relative to the true vertical line changed significantly in the normodivergent and hyperdivergent groups, whereas the lower lip position relative to the true vertical line changed significantly only in the hyperdivergent group (q < 0.05, FDR-adjusted p value). No other parameters showed significant within-group changes (q > 0.05). Intergroup comparisons revealed statistically significant differences in the magnitude of change for the nasolabial angle, the mentolabial angle, the upper and lower lip prominence, the upper and lower lips to the E-line, the lower lip position relative to the true vertical line, and the commissure depth (q < 0.05). In particular, between the hyperdivergent and hypodivergent groups, the nasolabial angle was approximately 1.67° and 0.90°, respectively, while the mentolabial angle was approximately 1.78° and 0.94°, respectively. No significant differences were observed for the remaining parameters (q > 0.05).
Conclusions:
Lip changes following bracket debonding varied according to vertical skeletal pattern. Frontal analysis showed stable morphology, while lateral analysis revealed lip retrusion, which was greatest in hyperdivergent patients. After bracket debonding, the lower lip had a numerically larger retrusion than the upper lip.
