Introduction
Facial expressions as a type of nonverbal communication play an essential role in daily conversations. When assessing emotions, facial expressions carry more weight than the spoken message [Since orthodontic treatment, and in particular orthodontic-surgical treatment, always affects the appearance of the facial soft tissue, three-dimensional (3D) imaging using stereophotogrammetry has become increasingly important in recent years. In orthodontic-surgical treatment, this helps to predict postsurgical soft tissue changes and to improve the surgical plan [Non-invasive, four-dimensional (4D) video stereophotogrammetry offers a modern and promising approach for the objective recording and evaluation of facial movements [The aim of the present study was to compare facial expressions before (T0) and after (T1) orthognathic surgery by implementing the novel method of 4D videostereophotogrammetry in orthodontics. We hypothesised that the magnitude, shape change, symmetry, and time of facial expressions change from T0 until T1.