The Relationship Between Obesity and Mandible Size in Children and Adolescents

Hypothesis: We hypothesize that there is a significant relationship between obesity and mandible size and shape in children and adolescents. Objective: To investigate the relationship between craniofacial morphology and size and the body mass index (BMI) of children and adolescents. Methods: The initial pre-treatment records of patients from the Orthodontics Department at the University of Illinois at Chicago (UIC) were reviewed retrospectively. Following the application of specific inclusion and exclusion criteria, 181 patients, both male and female, were included in the study. The subjects ranged from ages 9-19 years old. The height and weight measurements recorded at the time of initial records was used to calculate a raw body mass index (BMI) score. The raw BMI score was then used to identify each subject’s age and sex specific BMI percentile. Using the Center for Disease Control and Prevention (CDC) growth charts, each subject was categorized as either underweight, normal weight, overweight or obese. The tpsDig2 computer software program was used to digitally landmark 22 points on each lateral cephalometric radiograph (LCR). These landmarks were used quantify and analyze the size and shape of each mandible using geometric morphometrics. Results: 6 underweight subjects were identified as potential outliers and ultimately removed from the sample. Evidence of allometry, or size related shape differences, was detected and scaled out. Principal Component Analyses (PCA) were performed on the allometric regression residuals of mandibular shape. 6 of the 24 PCs yielded were representative of >5% of total shape variation of the mandible. A series of ANOVA test on PC1-6 using BMI category (normal, overweight, obese) as the grouping variable showed PC6 was approaching a significance difference across each BMI category. Partial correlation analyses revealed a positive relationship between increased BMI and centroid size of mandible (r=0.212, p=0.005) and craniofacial complex (r=0.168, p=0.029). Conclusions: Results are too ambiguous to make any clear clinical recommendations. Evidence was found of an association between high BMI and increased centroid size of the mandible and craniofacial complex. No statistically significant relationship was identified between obesity and shape in this subject population. Further study of this relationship is warranted. Funding: N/A IRB/ACC protocol: #2018-0716