Introduction: There is currently no consensus regarding the best method for predicting the changes in soft tissues due to the modification of hard tissues in orthognathic surgery.
Objective: To measure the changes in soft tissues of the upper lip, lower lip, and chin regions due to the modifications of hard tissues caused by orthognathic maxillary advancement surgery using a cephalometric methodology.
Methods: The study was conducted on 35 patients with dentoskeletal and facial deformities submitted to orthognathic maxillary advancement surgery. Two teleradiographs were taken: one during the preoperative period and the other 1 year after the surgery, on which the cephalometric tracing was drawn.
Results: A strong correlation (r = 0.747) was demonstrated in the horizontal analysis between the hard A (Ah) point (located in the deepest point of the anterior curvature of the maxilla) and the soft A (As) point in the advancement of the maxilla, with a mean variation of 0.859% occurring in As with each 1% variation of the Ah point. A mean variation of 0.698% occurred in the superior soft prostion point (prolongation of the superior hard prostion point to its corresponding point on soft tissue) for each 1% variation in the superior hard prostion point (bone point located at the junction of the alveolar process with the crown of the upper incisors).
Conclusion: The cephalometric methodology applied here revealed that the soft tissues of the upper lip accompanied 70 to 80% of the movement of hard tissues in maxillary advancement and that the soft tissues of the lower lip did not change or showed no significant changes.