Three-dimensional evaluation of smile characteristics in subjects with increased vertical facial dimensions.

Introduction: Patients seeking orthodontic treatment often have esthetic concerns (ie, they want a better smile). Patients with increased vertical facial dimensions have different smile traits than other patients. This study aimed to compare the smile characteristics of subjects with different vertical facial dimensions and to use stereophotogrammetry to evaluate the changes in facial animation upon smiling.

Methods: One hundred twenty adolescents and young adults (aged 15-25 years) who were referred for orthodontic treatment were divided into 2 groups according to their vertical facial height: increased (n = 30) and normal (n = 30). Three-dimensional stereophotogrammetric images were obtained from the patients during rest and smile. The images were superimposed, and the displacements of specific landmarks were recorded. Linear, angular, and proportional measurements were recorded on the smile and rest images.

Results: When smiling, horizontal movement of commissures was less (right, P = 0.038; left, P = 0.009), upper lip elevation was higher (P = 0.014), and the upper lip was shorter (P = 0.014) in the vertical group than in the normal group. In the vertical group, the interlabial gap was increased both at rest and when smiling (P <0.001). Statistically significant differences were found in smile index (P = 0.001), nasolabial fold displacement (P = 0.018), and lip angles (both P = 0.001) between groups.

Conclusions: Group and sex differences were observed when smiling. Careful consideration of these differences will help clinicians in proper diagnosis and treatment planning.