A post that has fractured in a root canal can pose a major problem. In such a situation the risk of root fracture or perforation during removal of the post remnant may be high. These fractured posts can often be loosened by using a ultrasonically powered chisel at the cement interface. The chisel breaks up the luting cement and the irrigant washes it away, and this in turn helps removal with the Masserann trepan which is used to cut down along the cement. Care must be taken to check the edges of the trepan, sharpening them when necessary. Occasionally the edges can flare out, with resultant danger of excessive removal of dentin and increased risk of weakening the root or even perforation. A smaller trepan can be used, as described in the silver point removal page, to grip the fractured portion.
If the fractured post is of the threaded type a groove cut in the end of it may enable it to be unscrewed, provided the cement seal is first weakened. If this is unsuccessful the Masserann kit can be used: the trepan should be of a diameter to cut along the threads of the post, as this will minimize the amount of dentine removed while easing cutting of the metal. If a Masserann kit is not available the post may have to be drilled out using an end-cutting bur. However, this becomes a more hazardous procedure as one gets higher up the canal.
See clinical sequence here.