Impact of obesity on orthodontic tooth movement in adolescents: a prospective clinical cohort study

Obesity is a widespread chronic inflammatory disorder characterized by an increased overall disease burden and significant association with periodontitis. The aim of this prospective clinical cohort study was to investigate the effect of obesity on orthodontic tooth movement. Fifty-five adolescent patients (27 males, 28 females) mean age 15.1 (SD, 1.7) years and mean body mass index 30.2 (3.5) in obese and 19.4 (2.2) kg/m2 in normal-weight groups were followed from start-of-treatment to completion of tooth alignment with fixed orthodontic appliances. Primary-outcome was time taken to complete tooth alignment, whilst secondary-outcomes included rate of tooth movement and change in clinical parameters (plaque/gingival indices, unstimulated whole mouth salivary flow rate, gingival crevicular fluid biomarkers). Data collection took place at baseline (start-of-treatment: appliance-placement); 1-hour and 1-week following appliance-placement; and completion-of-alignment. Results were analyzed by descriptive statistics followed by generalized estimating equation regression modelling. There were no significant differences between groups in time taken to achieve tooth-alignment (mean 158.7 days; SD 75.3; P=0.486). However, at 1-week initial tooth displacement was significantly increased in the obese group (P<0.001) and after adjusting for confounders, obese patients had a significantly higher rate of tooth movement compared to normal-weight (+0.017 mm/day; 95 CI: 0.008,0.025; P<0.001) over the period of alignment. Explorative analyses indicated that levels of the adipokines leptin and resistin, the inflammatory-marker myeloperoxidase and the cytokine receptor for nuclear factor kappa-B ligand (RANKL) were significantly different between obese and normal-weight patients and associated with observed rates of tooth movement. This represents the first prospective data demonstrating a different response in obese patients compared to normal-weight during early orthodontic treatment. These differences in the response of periodontal tissues to orthodontic force in the presence of obesity have potential short and long-term clinical implications.