Dynamic smile analysis in young adults

Introduction: Current trends in orthodontics place greater emphasis on smile esthetics, yet few studies provide averages and norms for the smile. The purposes of this study were to provide averages for various components of the smile and to compare some of these in orthodontically treated and untreated groups. Also, smiles of patients with and without rapid maxillary expansion (RME) were compared. Methods: Video equipment was used to capture smiles in 230 subjects. Results: The majority of subjects showed on smile flat smile arc, back to the second maxillary premolar, and an 11% buccal corridor. The orthodontically treated group showed a statistically significant more parallel smile arc compared with the untreated group. The RME group had statistically significant less buccal corridor compared with the nonexpanded subjects. Conclusions: This study helps to establish dynamic norms for the smile and shows that orthodontic treatment might not flatten the smile arc as previously suggested, and, furthermore, that RME appears to be associated with a decreased buccal corridor.