Main findings in context of the existing evidence—results
The main finding was that orthodontic-surgical treatment increases the magnitude of the facial expression maximum smile by approximately 13% (= 2 mm), while it decreases that of the facial expression lip purse by approximately 11% (= 1 mm). The parameters shape change, time, and symmetry of the movement demonstrated no relevant changes from T0 to T1. The novelty of videostereophotogrammetry makes it difficult to compare these results with existing evidence. There are first attempts to integrate the dynamics of facial motion in orthodontic-surgical research [Furthermore, the question arises whether 1 or 2 mm (11–13%) changes in the magnitude of the facial expressions, like found in the present study, are clinically relevant. With regard to social interaction the interpretation of the data gets even more complex as culture and gender shapes our expectations about the intensity of facial expressions in the sense of emotions [