目的: 通过临床及影像学评价罹患重度牙周炎下颌磨牙拔牙同期微翻瓣牙槽嵴保存的效果，探讨该术式的适应证。方法: 选择2013年9月至2021年6月于北京大学口腔医院牙周科因重度牙周炎拔除下颌磨牙患者的临床资料进行回顾性分析，根据微创拔牙后进行同期微翻瓣牙槽嵴保存术(micro crestal flap-alveolar ridge preservation，MCF-ARP)或仅清创处理后自然愈合分为微翻瓣牙槽嵴保存组(MCF-ARP组)和自然愈合组。通过对拔牙前或拔牙即刻(作为基线)及种植前(拔牙愈合后)拍摄的锥形束计算机断层扫描配准后分析骨高度、宽度和体积及其变化，并比较两组种植时同期引导骨再生(guided bone regeneration，GBR)的比例。结果: 共纳入87例患者96颗下颌磨牙，MCF-ARP组愈合后拔牙窝底中心处距离下颌管骨皮质最冠方的高度(中心骨高度)平均增加了(8.34±2.81) mm，自然愈合组平均增加了(3.82±3.58) mm，两组间差异有统计学意义(P < 0.001)。MCF-ARP组高骨壁骨嵴顶下1 mm处的牙槽骨宽度平均增加了(3.50±4.88) mm，自然愈合组牙槽嵴宽度减少了(0.16±5.70) mm，两组间差异有统计学意义(P=0.019)。MCF-ARP组愈合后的牙槽骨中心骨高度均大于8 mm，其中97.1%的牙槽骨中心骨高度>10 mm；自然愈合组愈合后有23.1%的牙槽骨中心骨高度 < 8 mm，仅61.5%的牙槽骨中心骨高度>10 mm。愈合后MCF-ARP组牙槽窝总体积、颊侧体积和舌侧体积增加量及增加比例均大于自然愈合组，两组间差异有统计学意义(P < 0.001)。MCF-ARP组68颗种植体有5颗(8.3%)种植同期进行GBR，自然愈合组26颗种植体有8颗(30.8%)种植同期进行GBR，两组间差异有统计学意义(P=0.003)。结论: 对于罹患重度牙周炎的下颌磨牙，如果拔牙前拔牙窝底中心处距下颌管骨皮质最冠方距离较小(＜7 mm)时，临床医生可考虑进行拔牙同期微翻瓣牙槽嵴保存术，为未来种植治疗时提供充足的骨量，减少种植同期进行引导骨再生的比例，降低种植治疗的难度与风险，提高种植治疗的安全性。

Objective: To evaluate the clinical and radiographic efficacy of micro crestal flap-alveolar ridge preservation following extraction of mandibular molars with severe periodontitis compared with natural healing, and to preliminarily propose the surgical indication. Methods: A retrospective analysis was conducted on clinical data from patients with mandibular molars with severe periodontitis either receiving micro crestal flap-alveolar ridge preservation (MCF-ARP group) or undergoing natural healing in department of periodontology, Peking University School and Hospital of Stomatology from September 2013 to June 2021. Cone-beam computed tomography scannings performed before/immediately after extraction (as baseline) and repeated before implantation (after the extraction socket healing) were used to measure the ridge width, height and volumetric changes of the sockets, and the proportion of guided bone regeneration (GBR) during implant therapy were compared between the two groups. Results: Between baseline and healing, significant differences in changes of MCF-ARP group [(8.34±2.81) mm] and natural healing group [(3.82±3.58) mm] in the distances from mandibular canal to center of the tooth socket were recorded (P < 0.001). The ridge width at 1 mm below the most coronal aspect of the crest increased by (3.50±4.88) mm in the MCF-ARP group but decreased by (0.16±5.70) mm in the natural healing group, respectively (P=0.019). After healing, the MCF-ARP group showed the distances from mandibular canal to center of the tooth socket >8 mm in all the cases, with 97.1% exceeding 10 mm. Natural healing group displayed 23.1% of the cases with center bone height < 8 mm and 61.5% exceeding 10 mm. Volume changes at the buccal and lingual aspect as well as the total socket were significantly greater in the MCF-ARP group compared with natural healing group (P < 0.001).At the time of implantation, GBR was performed in 5 out of 68 subjects (8.3%) in the MCF-ARP group, whereas 8 out of 26 subjects (30.8%) in the natural healing group required GBR, reflecting significant difference (P=0.003). Conclusion: In the sites of mandibular molars with severe periodontitis, when the distances from mandibular canal to center of the tooth socket was not enough (less than 7 mm), clinicians could consider performing the micro crestal flap-alveolar ridge preservation to achieve augmentation for alveolar ridge and reduce the proportion of guided bone regeneration during implant therapy to reduce the difficulty and risk of injuries during implant therapy.