Correlation Between Lip Prominence and Orthodontic Incisor Repositioning Within an Aesthetic Triangle Framework

Background: Accurate prediction of lip prominence changes following orthodontic treatment remains challenging because traditional profile analyses rely on isolated reference lines that do not account for combined nasal and chin morphology. The aesthetic triangle framework integrates these structures and may provide a more comprehensive evaluation of lip position. Methods: This correlative clinical study evaluated 82 orthodontic patients undergoing bimaxillary incisor repositioning. Lateral cephalograms and standardized profile photographs were obtained before and after treatment. Lip position was assessed relative to the aesthetic triangle boundaries, and dentoalveolar changes were quantified using standard incisor measurements. Lip thickness was analyzed as a potential modulating factor. Results: Orthodontic treatment produced significant incisor proclination and sagittal advancement. Within the aesthetic triangle framework, the lower lip demonstrated consistent anterior migration toward the central compartment following mandibular incisor advancement. In contrast, the upper lip showed minimal displacement despite substantial maxillary incisor movement. Mandibular incisor inclination significantly predicted lower lip migration, while maxillary incisor variables showed limited predictive value. Thinner lips exhibited greater positional responsiveness. Conclusions: The aesthetic triangle provides a clinically meaningful framework for interpreting orthodontic soft tissue changes as spatial migration rather than isolated linear measurements. Lower lip prominence responds predictably to dentoalveolar mechanics, whereas upper lip position is more constrained by soft tissue morphology.