1 Professor, Department of Orthodontics, School of Dentistry and Dental Research Centre, Tehran University of Medical Sciences

2 Post graduate student, Department of Orthodontics, School of Dentistry, Tehran University of Medical Sciences

3 Dentist



Introduction: Soft tissue changes and especially smile is one of the most important parameters in diagnosis and treatment planning in orthodontics. The main aim of this study was evaluating the correlation of the smile line with verticaldental parameters of occlusion.
Materials And Methods: In this cross sectional study, 46 patients (23 females and 23 males) aged between 18 to 25 years old were selected. The subjects were asked to pose a smile and several variables were measured and recorded which were mainly related to smile line. A lateral cephalometric radiography was ordered for each patient and anatomic landmarks were determined. And then correlation between 6 vertical dental parameters and some smile variables were analyzed. In order to determine association between quantitative variables, correlation coefficient of Pearson was used. P<0.05 was considered as significant. 
Results: There was significant correlation between palatal-occlusal plane with quantitative variables such as tooth-lower lip position and inter labial distance during smile. No significant correlation was seen with other smile variables. There was significant correlation between upper 6 to palatal plane with smile width but no correlation was found with other smile variables. Upper 6 to Frankfort plane had significant correlation with clinical crown and smile width but not with other smile variables.
Conclusion: According to the result of this study, dental vertical variables affect the vertical component of smile, which means vertical development in the dentition can lead to the distance between some vertical variables of posed smile.