Apical preparation

Once the coronal preparation is completed, the canal should be explored to full working length using fine hand files and the balanced force technique. The working length should be confirmed, and the canal enlarged to a size 15 or 20. If this is not done, the rotary instrument will have to cut at its tip, rather than along its length, which may lead to jamming and fracture. Each time a file is removed from a canal after use the position of the dentine debris in the flutes should be inspected. The instruments should cut along their entire length. If debris is only seen at the tip, the instrument may be excessively stressed, which may lead to fracture. The apical part of the canal may now be prepared with sequentially smaller instruments, stepping down the canal with
each smaller size. It may be necessary to return to a larger size during preparation (recapitulation) to create more space for the smaller instruments.