My wife had a root canal done on an upper bicuspid tooth 15 years ago for which she paid her dentist $600. This dentist has long since retired and emigrated to Israel. Our new dentist was surprised when she was having trouble with that same tooth. When he took X-rays he discovered that the previous dentist had left the metal files embedded in the 2 root canals and then filled and capped the tooth.
She wast sent to a specialty endodontist who will take 3 visits to remove these files from the tooth, (which is no easy job), at a cost of $850. It will then take another $1,500 to properly restore the tooth. Leaving files embedded in the root canals today is considered malpractice. However, I understand that at one time long ago it was considered standard safe practice to do so for a period of 2 years. My wife was unlucky in that that her first root canal was done during that 2 year period.
                                                       SOL