Facial and oral factors affecting smiles in young people

Objective To characterize smile morphology and examine its associations with facial and oral parameters, with emphasis on factors associated with smile attractiveness in Vietnamese young adults. Materials and methods Dynamic smiles of 490 Vietnamese individuals (mean age 21.04 ± 1.79 years) were recorded and analyzed. Categorical smile characteristics including anterior smile line, smile arc, upper lip curvature, most posterior tooth displayed, and upper teeth-lower lip relationship were assessed. Quantitative parameters comprised buccal corridor space, smile index, and dynamic smile symmetry. Multiple facial and dentofacial measurements were also obtained, including upper lip length, lip mobility, philtrum height, proportional indices, lip-line and occlusal plane cant, dental midline deviation, mouth size ratio, and incisal edge visibility. Participants were further classified according to smile attractiveness to identify associated determinants. Results The anterior smile line, smile arc, and upper lip curvature demonstrated broad associations with several dentofacial parameters. The most posterior tooth displayed was significantly related to the philtrum height–upper lip length ratio and incisal edge visibility. Buccal corridor space and smile index showed comparatively limited correlations. Dynamic smile symmetry was significantly associated with upper lip length during smiling and mouth size ratio at rest. Several soft tissue and dentofacial variables were identified as contributing factors to smile attractiveness. Conclusion Smile morphology in Vietnamese young adults is influenced by coordinated interactions between soft tissue dynamics and dentofacial proportions. These findings highlight population-specific characteristics and provide clinically relevant guidance for aesthetic evaluation and treatment planning in orthodontic and restorative practice.