If the separated instrument is screwed through the apex a surgical approach is usually indicated to free the fragment. If possible, the apex of the tooth should be removed and the fragment pushed up into the empty canal space. The root canal can then be cleaned and obturated at the time of surgery prior to placing the retrograde filling. If it is not possible to remove the fragment a retrograde amalgam filling should be placed and the canal cleaned and obturated as far as possible.
In the event of failure to remove a separated instrument it may be possible to bypass it, although in our experience it is difficult to bypass a separated instrument which lies in the apical third because the root canal is usually more circular in cross section in this area.