Abstract: Management of dental trauma cases is always a challenge for dentists. When crown-root subgingival fracture lines locate in close proximity to or below the alveolar bone crest due to traumatic injury，multidisciplinary assessments are indicated in order to create space for restoration. Modified crown lengthening is presented by conservative removal of the supporting alveolar bone in combination with reshaping the existing tooth surface，as a consequence of which the indication for crown lengthening has been broadened to reserve more natural teeth. This article illustrates a case of the maxillary lateral incisor with crown-root fracture caused by trauma undergoing modified crown lengthening and post-core crown restoration to get functional and esthetic recovery，and the 2-year follow-up shows satisfactory results，which provides experience for clinical management of such cases.

Key words: maxillary lateral incisor, modified crown lengthening, crown-root fracture, post-core crown

摘要： 牙外伤一直是口腔医生临床处置的难点。对于冠根折至龈下较深的外伤牙，需通过多学科综合评估，为最终保留创造修复条件。改良牙冠延长术通过少量去骨联合根面改形，拓宽了牙冠延长术的适应证，使冠根折断位于龈下较深的部分天然牙得以保留。文章完整展示了1例外伤导致折裂的上颌侧切牙通过改良牙冠延长术及桩核冠修复恢复功能与美观的诊治过程，随访2年的临床效果令人满意，为推广此类病例实施改良牙冠延长术保留患牙提供了一定的经验。

关键词: 上颌侧切牙, 改良牙冠延长术, 冠根折, 桩核冠