This tooth has cracks on all four sides around the old silver filling.  After it was removed a white medicine can be seen that was appropriately placed long ago before the silver was placed on top.  This should be removed to get at the bottom of the cracks to properly remove all remaining tooth decay.  The result is a tooth preparation that is deep and close to the nerve.  Sometimes post operative tooth pain requires root canal therapy to be performed by an Endodontist.

Removal of a deep cavity and why some teeth may also need Root Canal.