英语语法分析

It is conventionally performed through a hole drilled into the crown of the affected tooth, namely orthograde root canal therapy.

根管治疗手术通常通过在受影响的牙齿牙冠中钻孔完成，即矫正根管治疗。

For teeth that cannot be treated with orthograde root canal therapy, or for which it has failed, retrograde root filling, which seals the root canal from the root apex, is a good alternative.

对于不能用矫正根管治疗或用次治疗失败的牙齿，根尖倒充填(其将根管从根尖密封)是个良好的替代方案。