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The study of three-dimensional smile changes on orofacial morphology
Johnson Hsin-Chung Cheng1,2, Yu-Chien Hsu1,2, Od Bayarsaikhan3
1School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei City, Taiwan.
Journal of Dental Sciences
|April 14, 2025
Summary
This study reveals significant three-dimensional (3D) changes in orofacial soft tissues during smiling, primarily in the z and y-planes. These findings highlight the limitations of 2D analysis and emphasize the importance of 3D assessment in orthodontic planning.
Area of Science:
- Orthodontics
- Dentofacial Orthopedics
- Facial Aesthetics
Background:
- Traditional 2D facial analysis offers limited insight into 3D craniofacial relationships.
- Understanding dynamic 3D soft tissue changes during smiling is crucial for comprehensive facial assessment.
Purpose of the Study:
- To investigate the three-dimensional (3D) alterations in orofacial soft tissues during smiling.
- To explore the influence of craniofacial and dental morphology on these dynamic 3D smile changes.
Main Methods:
- Recruited 131 individuals (18-30 years) with attractive facial features.
- Captured 3D facial images and cone-beam computed tomography (CBCT) scans at rest and during a posed smile.
- Analyzed 23 landmarks, 11 linear, and 6 angular measurements to assess 3D smile dynamics.
Main Results:
- Significant differences in soft tissue landmarks were observed across all three planes (x, y, and z) during smiling.
- The most pronounced changes occurred in the z and y-planes, which are not fully captured by traditional 2D methods.
- Correlations were found between upper and lower lip lengths and hard tissue measurements.
Conclusions:
- Dynamic 3D soft tissue changes during smiling are significant and predominantly occur in the z and y-planes.
- Orthodontic diagnosis and treatment planning should incorporate 3D analysis, particularly considering z-plane changes often missed in 2D assessments.
