Sometimes people may have this pain after the filling, which implies that the caries was not completely removed, and it has now reached the pulp, leading to pain. This may also mean that there has been a reinfection at the site of the filling. If a person complains of root canal pain after procedure, then it could mean that the root canal done was faulty or that the infection has restarted in the periapical region, that is, the region surrounding the tip of the root.