根管预备旨在清除根管系统内的细菌及毒素、残余牙髓,扩大根管,除去根管壁感染牙体质,休整管壁,除去管内残余的物质和碎屑,为根管充填创造良好的条件。根管预备的一个重要的标准为:预备后的根管最狭窄处应与原根管狭窄处相重合,即根管预备在精确的有效工作长度中进行。但是在根管预备过程中超工作长度预备是不可避免的,有报道~([1])显示尽管在X线片上工作长度距根尖孔约0~2mm,超根管预备发生率高达22%~50%。以往,学 Root canal preparation aims to remove bacteria and toxins in the root canal system, residual pulp, expand the root canal, remove the root canal wall infection of tooth texture, rest pipe wall, remove the tube of residual material and debris, to create a good root canal filling conditions of. An important criterion for root canal preparation is that the narrowest root canal after the preparation should coincide with the original root canal stenosis, that is, the root canal preparation should be performed in an accurate and effective working length. However, in the process of root canal preparation, it is inevitable that the length of super-working is inevitable. It has been reported that although the working length on the X-ray film is about 0 ~ 2mm away from the apical foramen and the rate of preparation of the extra-root canal is as high as 22% 50%. In the past, learn