Smile Line and Arc Most Broadly Linked to Facial Proportions
An analysis of the dynamic smile of 490 young adult Vietnamese individuals (average age 21.04 years) showed that the smile line, smile arc, and upper lip curvature are associated with a range of dentofacial measures, while buccal corridors and smile index showed limited correlations.
Three Smile Features Have the Most Connections with Soft Tissues and Teeth
Researchers captured and analysed the dynamic smile of 490 young adult Vietnamese individuals with an average age of 21.04 ± 1.79 years. The aim was to describe the morphology of the smile in this population and determine which facial and oral cavity measures are associated with how the smile appears and its perceived attractiveness.
Five categorical features were assessed: anterior smile line, smile arc, upper lip curvature, the most distal tooth visible in the smile, and the relationship of the upper teeth to the lower lip. Quantitatively measured were buccal corridors, smile index, and dynamic smile symmetry. Additionally, a range of facial measures was collected: upper lip length and mobility, philtrum height, proportional indices, inclination of the lip line and occlusal plane, dental midline deviation, mouth size ratio, and visibility of incisal edges.
The anterior smile line, smile arc, and upper lip curvature showed broad associations with multiple dentofacial parameters. The most distal visible tooth was significantly associated with the philtrum height to upper lip length ratio and the visibility of incisal edges. Dynamic symmetry was associated with the upper lip length in a smile and the mouth size ratio at rest.
Two parameters often highlighted in esthetic analysis, buccal corridors and smile index, showed relatively limited correlations. When subjects were categorised by smile attractiveness, multiple soft tissue variables and dentofacial relationships were identified as contributing factors, rather than a single measure.
Limitations
The sample consists of young adults from a single population, and the authors themselves mention population-specific features; applicability to other groups has not been verified. The summary does not provide effect sizes or information on funding.
For your practice
- Evaluate smiles using video or in motion, not just static photographs: the study measured dynamic smiles.
- In esthetic analysis, give weight to upper lip length and mobility, and philtrum height, not just teeth and buccal corridors.
- Do not automatically apply norms from one population to your patients.