200 Participants in this retrospective study were recruited from pre-orthodontic treatment patients in Taipei Medical University Hospital between 2019 and 2021. Patients above 10 years old were included and their extra-oral photographs and lateral cephalograms were collected. The cephalograms were analyzed to classify patients according to their facial types (ANB, FMA) and occlusal relationships (OJ, OB), and all patients' pre-treatment smiling photographs were measured for landmark positioning and linear measurement of smile analysis variables. 

Independent sample t-test was used to compare smile characteristics between males and females, while one way ANOVA analysis was used to compare whether there were differences in smile characteristics between groups with different facial types (ANB, FMA) or occlusal relationships (OJ, OB), with Scheffe post-hoc tests being performed to identify which specific groups showed significant differences. 

Furthermore, we measured the smile characteristics variables from relaxing to smiling positions and compared whether there were differences in soft tissue changes during smiling among different groups. 

Finally, multiple linear regression analysis was performed to investigate the potential factors related to various craniofaciodental types that may influence smile characteristics.