关键词: 安氏Ⅱ类错??畸形, 稳定性, 拔牙正畸, 侧貌突度

Abstract: Objective    To compare the long-term stability of facial profile protrusion in adolescent patients with Angle class Ⅱ malocclusion treated with two different extraction orthodontic modalities，thereby providing evidence for clinical decision-making. Methods    A retrospective analysis was performed on the clinical and radiographic data of 30 adolescent patients with Angle class Ⅱ malocclusion who were treated at the Department of Orthodontics，Shenyang Stomatological Hospital between September 2016 and August 2017. Based on the extraction orthodontic treatment plan，the patients were divided into two groups：the maxillary extraction group（extraction of bilateral maxillary first premolars）and the bimaxillary extraction group（extraction of bilateral maxillary first premolars and bilateral mandibular second premolars），with 15 patients in each group. Cephalometric landmark identification and displacement measurement analysis were conducted on lateral cephalograms taken before orthodontic treatment（T0），at the end of orthodontic treatment（T1），and 5 years after treatment （T5）. The landmarks were recorded as follows：nasion（N，N'，N''），soft-tissue nasion（Ns，Ns'，Ns''），point A （A，A'，A''），soft-tissue A-point （As，As'，As''），point B（B，B'，B''），soft-tissue B-point（Bs，Bs'，Bs''），upper incisor edge（UIE，UIE'，UIE''），lower incisor edge（LIE，LIE'，LIE''），upper lip（UL，UL'，UL''），lower lip（LL，LL'，LL''），pogonion（Pog，Pog'，Pog''），and soft-tissue pogonion（Pos，Pos'，Pos''）. Results    At the T1-T0 interval，a significant intergroup difference was only observed in the displacement of LIE'-LIE（t = 1.822，P = 0.016）. At the T5-T0 interval，significant intergroup differences were found in the displacements of LIE''-LIE，Pog''-Pog，and LL''-LL（P < 0.05）. Significant intra-group changes between T1-T0 and T5-T0 displacements were observed：in the maxillary extraction group，LIE'-LIE retracted from（0.79 ± 2.35）mm to（-0.82 ± 0.51）mm，and Pog'-Pog retracted from（1.95 ± 2.66）mm to（0.65 ± 0.41）mm；in the bimaxillary extraction group，LL'-LL protruded from（-1.66 ± 2.91）mm to（1.12 ± 0.87）mm；all the differences were of statistical significance（P < 0.05）. For the T5-T1 displacements，the absolute values of LIE''-LIE' and LL''-LL' exceeded 1 mm in both groups；and the maxillary extraction group showed a greater absolute value of LIE''-LIE' than the bimaxillary extraction group（P < 0.05）. Conclusion    Both extraction modalities achieve similar improvements in the facial profile of adolescent patients with Angle class Ⅱ malocclusion. Regarding long-term stability，bimaxillary extraction orthodontic treatment may be more favorable for maintaining mandibular incisor position and chin morphology but carries a risk of compensatory lip protrusion. Maxillary extraction alone faces challenges of lower incisor relapse and chin retraction. The essence of clinical decision-making in orthodontic treatment lies in weighing the long-term stability of teeth and skeleton against the harmony of the soft-tissue profile.

Key words: Angle class Ⅱ malocclusion, stability, extraction orthodontics, facial profile protrusion