ObjectiveTo investigate the effect of different soft-tissue morphologies on the treatment of skeletal class Ⅰ malocclusion patients by analyzing measurement data before and after treatment.MethodsPre- and post-treatment lateral cephalograms of 55 adult female Angle class Ⅰ patients were collected in the Department of Orthodontics, Hospital of Stomatology, Jilin University from January 2012 to December 2020. Chin soft-tissue morphologies in the lateral cranial radiographs were used to divide the patients into an abnormal chin morphology group (flat and retracted chins,n=27) and a normal chin morphology group (rounded and prominent chins,n=28). Relevant soft- and hard-tissue indexes were selected to study in-group varieties and intergroup differences in the varying chin morphologies before and after treatment.ResultsThe chin-lip angle, mandibular chin angle, mandibular chin vertex angle, PP-MP, LL-E, UL-E, Po-Pos, and B-B’ thickness in the abnormal chin morphology group were significantly higher than those in the normal chin morphology group (P<0 .05). furthermore, m∶bme and n∶b’mes in the abnormal chin morphology group were signi-ficantly lower than those in the normal chin morphology group (P<0 .05). after treatment, the mandibular chin angle, mandibular chin vertex angle, u1-sn, l1-mp, ll-e, ul-e, sna, snb, and b-b’ thickness of the abnormal chin morphology group significantly decreased (P<0 .05), whereas the nasolabial angle, m∶bme, n∶b’ mes, and po-pos significantly increased (P<0 .05). in the normal chin morphology group, the u1-sn, l1-mp, ll-e, ul-e, and b-b’ thicknesses decreased significantly (P<0 .05), whereas the nasolabial angle significantly increased (P<0 .05). among them, m∶bme and n∶b’ mes were positively correlated.ConclusionChin morphology affects the formulation of treatment plans. Compared with the normal chin morphology group, the abnormal chin morphology group required a larger retraction of incisors. Although the chin of soft-tissue morphology is related to the morphology of bones, the changes in soft tissue chin after treatment cannot be directly predicted according to the bone changes. Soft-tissue chin morphology affects the aesthetic assessment of the soft-tissue lateral profile and the change in soft tissue before and after treatment. The method of predicting the change in soft-tissue chin after treatment should consider the morphology of the soft-tissue chin.
