Abstract: Objective    To evaluate the effect of resection root length and crown-root ratio on the result of endodontic microsurgery in the treatment of apical cysts，providing guidance for clinical treatment. Methods    A retrospective analysis of 116 apical cyst patients with 164 teeth treated by endodontic microsurgery in the Affiliated Stomatological Hospital of Zhejiang University from January 2018 to June 2021 was performed. According to the surgical method，the patients were divided into two groups，which were 43 cases（75 affected teeth）in the root resection group and 73 cases（89 affected teeth）in the root-end filling group. Based on the cone beam CT images of the two groups before and 12 months after surgery，the relevant indexes of teeth ［anatomical root length（ARL），clinical root length（CRL），root length involved in cyst（RLC），resection root length（RRL），ratio of RRL to RLC（RRL/RLC），anatomical crown-root ratio（ACR），clinical crown-root ratio（CCR），relative change of anatomical crown-root ratio（RACR），relative change of clinical crown-root ratio（RCCR）］ were measured and calculated. The differences of the relevant measurement indexes of the affected tooth among different efficacy（cured，effective and ineffective）were compared. Results    In the root resection group，13 affected teeth were cured，40 teeth were effectively treated，and 22 teeth were ineffective，while there were significantly differences in ARL，CRL，ACR，CCR，RRL/RLC，RACR and RCCR among groups of different efficacy 12 months after surgery（all P < 0.05）. Among them，the ARL and CRL of the cured teeth were significantly greater than those of the ineffective teeth 12 months after surgery，while the ACR and CCR were smaller. The RRL/RLC，RACR and RCCR of cured teeth were smaller than those of ineffective teeth，and the differences were statistically significant （all P < 0.05）. In the root-end filling group，36 affected teeth were cured，33 teeth were effectively treated，and 20 teeth were ineffective. Only the RRL/RLC index showed that the effective tooth was significantly smaller than the ineffective tooth（P < 0.05），while the other difference was not statistically significant（P > 0.05）. Conclusion    When endodontic surgery is performed for apical cyst，especially when only microapectomy is performed，the length of apical resection and crown-root ratio have a certain impact on the curative effect，and it is necessary to avoid removing the excessive length of root of teeth，which affects the long-term prognosis of the affected teeth.

Key words: apical cyst, endodontic microsurgery, crown-root ratio, prognosis

摘要： 目的    研究根尖切除长度和冠根比对显微根尖手术治疗根尖囊肿效果的影响，为临床治疗提供指导意见。方法    选择2018年1月至2021年6月于浙江大学医学院附属口腔医院口腔颌面外科行显微根尖手术治疗根尖囊肿的116例患者临床和影像学资料行回顾性分析，共计患牙164颗。根据患者的手术术式分为2组，分别为根切组43例（75颗患牙）和倒充填组73例（89颗患牙）。基于2组患者术前和术后12个月的锥形束CT影像，测量和计算牙体相关指标［解剖牙根长度（ARL）、临床牙根长度（CRL）、囊肿累及牙根长度（RLC）、截根长度（RRL）、RRL与RLC之比（RRL/RLC）、解剖冠根比（ACR）、临床冠根比（CCR）、解剖冠根比相对变化百分比（RACR）、临床冠根比相对变化百分比（RCCR）］。比较2组不同疗效（治愈、治疗有效、治疗无效）患牙牙体相关指标测量结果差异。结果    根切组治愈患牙13颗、治疗有效患牙40颗、治疗无效患牙22颗，不同疗效患牙术后12个月的ARL、CRL、ACR、CCR，以及RRL/RLC、RACR、RCCR总的比较，差异均有统计学意义（均P < 0.05）。其中，术后12个月治愈患牙的ARL和CRL均显著大于治疗无效患牙，ACR和CCR均小于治疗无效患牙；治愈患牙的RRL/RLC、RACR和RCCR也是小于治疗无效患牙的，差异均有统计学意义（均P < 0.05）。倒充填组治愈患牙36颗、治疗有效患牙33颗、治疗无效患牙20颗；仅RRL/RLC指标，治疗有效患牙显著小于治疗无效患牙，差异有统计学意义（P < 0.05）；不同疗效患牙其他牙体相关指标比较，差异均无统计学意义（均P > 0.05）。结论    在行显微根尖手术治疗根尖囊肿时，特别是仅行显微根尖切除术时，根尖切除长度和冠根比对疗效可能具有一定影响，应避免切除过长牙根影响患牙长期预后。

关键词: 根尖囊肿, 显微根尖手术, 冠根比, 预后