Limitations
The participants of the study were not operated on by the same surgeon, but all surgeries were performed at a single centre following the same stringent protocol. Since a multi-centre study revealed that even different surgeons at different centres obtain similar accuracy when following a virtual treatment plan [It is possible that the patients’ compliance, the intensity of care provided by the orthodontic-surgical treatment team, and subsequently the speed of post-surgical recovery were influenced by the fact that the patients were part of a clinical trial. Because of that Hawthorne effect, the participants in the present study might show increased facial expressiveness.The observed changes in maximum smile and lip purse were rather small. Due to the novelty of the method, there are no reference values which indicate what amount of change should be considered clinical relevant and what extent of change is detected by orthodontists, surgeons, laypersons, or the patients themselves. Future studies are needed to generate norm values.