Impact of orthodontic-induced facial morphology changes on aesthetic evaluation: a retrospective study

The profound influence of orthodontic treatments on facial aesthetics has been a topic of increasing interest. This study delves into the intricate interplay between orthodontic treatments, facial feature alterations, and aesthetic perceptions. A total of 73 patients who had undergone orthodontic treatment were included in this study. Facial photographs were taken before and after treatment. Ten orthodontists provided facial aesthetic ratings (FAR) for each patient's frontal, profile, and overall views. 48 facial landmarks were manually placed by the orthodontists and normalized using Generalized Procrustes analysis (GPA). Two types of phenotypes were derived from facial landmarks. Global facial phenotypes were then extracted using principal component analysis (PCA). Additionally, 37 clinical features related to aesthetics and orthodontics were extracted. The association between facial features and changes in FAR after orthodontic treatment was determined using these two types of phenotypes. The FAR exhibited a high correlation among orthodontic experts, particularly in the profile view. The FAR increased after orthodontic treatment, especially in profile views. Extraction of premolars and orthognathic surgery were found to result in higher FAR change. For global facial phenotypes, the most noticeable changes in the frontal and profile views associated with FAR occurred in the lip area, characterized by inward retraction of the lips and slight chin protrusion in the profile view, as well as a decrease in lip height in the frontal view. The changes observed in the profile view were statistically more significant than those in the frontal view. These facial changes were consistent with the changes from orthodontic treatment. For clinical features, two profile features, namely pg.sm.hori and pg.n.ls, were found to be associated with FAR following orthodontic treatment. The highest FAR scores were achieved when pg.sm.hori was at 80° and pg.n.ls was at 8°. On the other hand, frontal clinical features had a subtle effect on FAR during orthodontic treatment. This study demonstrated that orthodontic treatment improves facial aesthetics, particularly at lip aera in the profile view. Profile clinical features, such as pg.sm.hori and pg.n.ls, are essential in orthodontic treatment which could increase facial aesthetics.