The major problem with sub-gingival fracture is absence of adequate coronal ferrule and a compromised biological width. This usually complicates the application of the rubber dam during endodontic treatment. The primary objective of tooth extrusion or forced eruption is to provide both a sound tissue margin for ultimate restoration and to create a periodontal environment (biological width) that will be easy for the patient to maintain. Ingber et al. suggested that a minimum distance of 3 mm is required from the restorative margin to the alveolar crest to permit adequate healing and restoration of the tooth that is biologically acceptable.
图1. 一位40岁的女性患者右上第一前磨牙腭尖折裂就诊。临床检查显示腭侧折裂线延伸至龈下，很难修复。
A 40-years-old female patient presented to my private dental clinic with fracture of palatal cusp of upper right first premolar.
Clinical examination showed fractured line extended sub-gingival on the palatal side making the prosthetic rehabilitation difficult.
图2. 治疗的主要目的是在生物学上、功能上和美学原则等方面恢复受损的牙齿。
The main objective of the treatment was to restore the traumatised tooth in respect to all biological, functional and aesthetic principles of all the treatments involved.
图3. 然而，由于折裂位置深无法隔离患牙，需行牙冠延长术。最终决定正畸牵引是最好、最保守的选择。正畸托槽在折裂牙上粘接于更靠近根方的位置，钢丝牵引一个月，橡皮圈牵引3周。
However, as tooth isolation was not possible due to the deep fracture, lengthening of the clinical crown had to be performed. It was decided that orthodontic extrusion was the best and most conservative option. Orthodontic brackets was positioned in its place and more apically on fractured tooth. The time required for wire application is one month and 3 weeks for power chain.
图4. 最少量的牙龈成形术以获得均匀的牙龈边缘。
Minor gingival re-contouring was carried out in order to have a symmetrical gingival margin.
图5. 冠向牵引的效果很不错，折裂位置已达游离龈水平，可行有效的橡皮障隔离。正畸钢丝拆除。
The coronal extrusion was considered satisfactory as the fractured site had reached the free gingiva level, allowing for a qualitative RDI. Orthodontic wire was removed.
图6. 放置环状成形片。
Band placement.
图7. 复合树脂重建。
Composite build up.
图8. 复合树脂修复邻牙（尖牙）。
Composite restoration of adjacent tooth (canine).
图9. 放置主尖。
Master cone in place.
图10. 试主尖X线片。
Master cone radiograph.
图11. 桩道预备。
Post preparation.
图12. 纤维桩就位。
Insertion of fiber post.
图13. 复合树脂修复。
Composite restoration.
图14. 颊侧观。
Facial view.
图15. 术后片。
Obturation radiograph.
总结
In cases of crown fractures, where endodontic treatment is required and proper field isolation is impossible due to subgingival crown fracture, coronal extrusion of the remaining root via orthodontics, is a viable option before the completion of the root canal and the subsequent coronal restoration under optimal conditions.
