Abstract:Objective To observe the changes of bone density and morphology of the upper airway in obese children, and understand their diet and sleep situation and past history of oral diseases, so as to investigate the correlation between obesity and Angel class Ⅱ malocclusion deformity in children. Methods Body mass index (BMI) was examined for 895 children of 11-12 years. The 170 children with BMI ≥ 23 were enrolled into obesity group, 170 children were randomly chosen from the remaining 725 with BMI < 23 into matched normal group. Bone mineral density was determined in both groups, and related parameters of soft and hard tissues in upper respiratory tract were calculated. Questionnaire survey was conducted to understand children's diet, sleep and past history of oral diseases. Results In the obesity group, bone mineral density reduced, upper airway was relatively narrow, the incidence of mouth breathing habit and early tooth loss was relatively high. Conclusions Although obesity does not immediately cause Angel class Ⅱ malocclusion, it has an indirect correlation with Angel class Ⅱ malocclusion deformity.