Facial esthetics is a major concern of orthodontic patients. This study aims to evaluate orthodontic\ntreatment-related thickness changes of the masseter muscles and surrounding soft tissues and the potential factors\nthat would influence these changes during orthodontic treatment in female adults.\nMethods: Forty-two female adult patients were included in this retrospective study and were divided into\nextraction (n = 22) and nonextraction (n = 20) groups. Pretreatment and posttreatment cone-beam computed\ntomography (CBCT) images were superimposed and reconstructed. The thickness changes of the masseter area of\nfacial soft tissue (MAS), masseter muscles (MM) and surrounding fat tissue (FT) were measured. Pretreatment age,\ntreatment duration, sagittal relationship (ANB), and vertical relationship (Frankfort-mandibular plane angle, FMA)-\nrelated MAS, MM and FT changes were compared between extraction and nonextraction groups. Spearmanâ??s\ncorrelation coefficient was calculated between the above variables. Regression analysis was conducted to confirm\nthe causal relations of the variables.\nResults: The thickness of MAS and MM significantly decreased in both groups, with larger decreases...................
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