Influence of body mass index on perceived lower facial asymmetry

Facial asymmetry plays a crucial role in facial esthetics, and factors such as body mass index may influence its visibility by altering soft tissue thickness, which can lead to differences in how orthodontists, dentists, and laypeople perceive lower facial asymmetry. This discrepancy can affect aesthetic evaluations and treatment expectations. The aim of this study is to evaluate the perceptibility of lower facial asymmetry among individuals with different body mass indices as assessed by orthodontists, dentists, and laypeople. Frontal photographs were obtained from four female models representing different body mass index (BMI) categories, severely underweight (U), normal weight (N), obesity class I (OI), and obesity class III (OIII), ranging from 16.1 to 41.8. All models exhibited symmetrical lower faces. To simulate asymmetry, each image was digitally altered by rotating the chin clockwise by 2°, 4°, and 6°. A web-based survey was created featuring 20 randomly arranged images (five per model). Participants, comprising 97 orthodontists, 86 dentists, and 86 laypeople, rated each image using a 7-point Likert scale (1 = no asymmetry, 7 = maximum asymmetry). Statistical analysis was performed using the Kruskal–Wallis test to evaluate intergroup differences, followed by pairwise comparisons with the Mann-Whitney U test (p < 0.05). For models in the U, N, and OI categories, orthodontists and dentists detected minimal deviations of approximately 2.5 mm, whereas laypeople identified deviations of about 3.4 mm or greater. In the OIII category, the threshold for orthodontists increased to 3.41 mm, while neither dentists nor laypeople were able to perceive asymmetry. Body mass index has a significant influence on the perception of lower facial asymmetry. As BMI increases, the perceptibility of lower facial asymmetry decreases. Orthodontists demonstrate greater sensitivity in detecting lower facial deviations compared with dentists and laypeople. Clinically, orthodontists should consider BMI-related changes in soft-tissue balance, as weight variation may influence facial symmetric perception and treatment expectations.